Radiation detector and radiation detector array

Abstract

To provide a radiation detector having high time resolution and high energy resolution.SOLUTION: The substrate 11 has a first part 21 which is covered with the side faces of the scintillators and in which the plurality of light detection areas 23a and 23d are arranged, and a second part 22 which is arranged side by side with the first part 21 in the first direction D1 and is exposed from the side faces of the scintillators. The lengths of the scintillators at the D1 in the first direction are greater than the lengths of the scintillators at the D2 in the second direction. The lengths of the side surfaces of the scintillators at the first direction D1 are greater than the widths of the side surfaces of the scintillators at the third direction D3. In the second portion 22, the electrodes 14a connected to the light detection region 23a via the conducting wires 17a and the electrodes 14d connected to the light detection region 23d via the conducting wires 17d are arranged. The light detection region 23d is closer to the second portion 22 than the light detection region 23a. The line 14a is wider than the line 14d.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to radiation detectors and radiation detector arrays. [Background technology]

[0002] A radiation detector is known that includes a hexahedral scintillator and a semiconductor photodetector element that has a semiconductor substrate disposed on the scintillator (see, for example, Patent Document 1). The scintillator generates scintillation light when exposed to radiation, and the generated scintillation light is detected by the semiconductor photodetector element. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2015-83956 Summary of the Invention [Problem to be solved by the invention]

[0004] An object of the first and second aspects of the present invention is to provide a radiation detector having high time resolution and high energy resolution, and an object of the third and fourth aspects of the present invention is to provide a radiation detector array including radiation detectors having high time resolution and high energy resolution. [Means for solving the problem]

[0005] The present inventors have conducted extensive research into radiation detectors with high time resolution and high energy resolution. As a result, the present inventors have newly obtained the following findings, which led to the present invention. Patent Document 1 does not disclose a radiation detector with high time resolution and high energy resolution. When radiation is incident on one of a pair of end faces of a scintillator that is long in the first direction, the scintillator reliably absorbs radiation in the high-energy range and generates scintillation light. In a configuration in which a semiconductor photodetector element is disposed on the other end face of the pair of end faces, radiation in the high-energy range is more likely to be reliably absorbed. However, this configuration makes it difficult to achieve high time resolution. The semiconductor photodetector element detects scintillation light that is directly incident on the other end face. The semiconductor photodetector element also detects scintillation light that is reflected by one end face and then incident on the other end face. These two scintillation lights are generated simultaneously within the scintillator. However, these two scintillation lights are detected by the semiconductor photodetector element with a large time difference. Detection with high time resolution is difficult. Therefore, in a radiation detector, it is desirable to position the semiconductor photodetector element at a position where the simultaneously generated scintillation lights can be detected without a significant time difference. With this positioning of the semiconductor photodetector element, incident radiation can be detected with high time resolution. The higher the energy of radiation incident on the scintillator, the more the scintillator light is generated at a position farther away from the one end face in the first direction. The magnitude of the radiation energy is correlated with the distance from the one end face of the scintillator. In a configuration in which the semiconductor photodetector element has one photodetection region that detects scintillation light, it is difficult to measure the distance from the one end face of the scintillator. Therefore, it is desirable that the semiconductor photodetector element has a plurality of photodetection regions arranged in the first direction. With a configuration of the semiconductor photodetector element in which a plurality of photodetection regions are arranged, incident radiation can be detected with high energy resolution.

[0006] A radiation detector according to a first aspect includes a scintillator having a pair of end faces facing each other in a first direction and side faces connecting the pair of end faces, a semiconductor photodetector element having a semiconductor substrate arranged to face the side faces, and a wiring member electrically connected to the semiconductor photodetector element. The length of the scintillator in the first direction is greater than the length of the scintillator in a second direction perpendicular to the side faces. The length of the side faces in the first direction is greater than the width of the side faces in a third direction perpendicular to the first and second directions. The semiconductor substrate is covered with the side faces and has a first portion in which multiple photodetection regions are arranged, and a second portion aligned with the first portion in the first direction and exposed from the side faces. The multiple photodetection regions are aligned in the first direction, and each includes at least one avalanche photodiode operating in Geiger mode, and at least one quenching resistor electrically connected in series with one of the anode and cathode of a corresponding one of the at least one avalanche photodiodes. The second portion includes a plurality of first electrodes electrically connected to at least one quenching resistor included in a corresponding one of the plurality of photodetection regions, and a second electrode electrically connected to the other of the anode and the cathode of each avalanche photodiode. The wiring member has a plurality of conductors electrically connected to corresponding one of the plurality of first electrodes, and a conductor connected to the second electrode.

[0007] According to the first aspect, the radiation detector includes a scintillator that is long in a first direction and a semiconductor photodetector element that is arranged on a side of the scintillator. The semiconductor photodetector element detects not only scintillation light that is directly incident on the side surface on which the semiconductor photodetector element is arranged, but also scintillation light that is incident on the side surface after being reflected by another side surface that faces the side surface on which the semiconductor photodetector element is arranged. Because the length of the scintillator in the second direction is shorter than the length of the scintillator in the first direction, the scintillation light that is directly incident on the side surface and the scintillation light that is incident on the side surface after being reflected by the other side surface are detected by the semiconductor photodetector element with a small time difference. Therefore, the first aspect achieves high time resolution. According to the first aspect, the radiation detector includes a semiconductor photodetector element having a plurality of photodetection regions arranged in a first direction. For example, the distance in the first direction between the point of generation of scintillation light and one end face of the scintillator can be determined from the position of the photodetection region that detects the most scintillation light among the plurality of photodetection regions. As a result, the magnitude of the energy of the radiation incident on the scintillator can be accurately measured. Therefore, the first aspect achieves high energy resolution.

[0008] In the first aspect, at least one of the pair of end faces may be inclined with respect to the second direction. In a configuration in which at least one of the end faces is inclined with respect to the second direction, the scintillation light is more reliably incident on the side face facing the semiconductor substrate. Since the number of times the scintillation light is reflected by the end face or side face is reduced and the return loss is also reduced, this configuration more reliably improves the amount of light received by the semiconductor photodetector element.

[0009] In the first aspect, of the pair of end faces, the end face extending in the second direction may have a cross section with a triangular wave shape. In a configuration in which the cross section of the end face extending in the second direction has a triangular wave shape, the scintillation light is more reliably incident on the side face facing the semiconductor substrate. Since the number of times the scintillation light is reflected by the end face or side face is reduced and return attenuation is also reduced, this configuration more reliably improves the amount of light received by the semiconductor photodetector element.

[0010] In the above one aspect, of the pair of end surfaces, the end surface extending in the second direction may be a rough surface. In a configuration in which the end face extending in the second direction is roughened, the scintillation light is more reliably incident on the side face facing the semiconductor substrate. Since the number of times the scintillation light is reflected by the end face or side face is reduced and return attenuation is also reduced, this configuration more reliably improves the amount of light received by the semiconductor photodetector element.

[0011] In the first aspect, the scintillator may have another side surface that connects the pair of end surfaces and is adjacent to the side surface, and has a triangular wave-shaped cross section. In the case where the cross section of the other side surface is triangular wave shaped, the scintillation light is more reliably incident on the side surface facing the semiconductor substrate, and therefore this configuration more reliably improves the amount of light received by the semiconductor photodetector element.

[0012] In the first aspect, the scintillator may have another side surface that is a rough surface and connects the pair of end surfaces and is adjacent to the side surface. In the case where the other side surface is roughened, the scintillation light is more reliably incident on the side surface facing the semiconductor substrate, and therefore this configuration further reliably improves the amount of light received by the semiconductor photodetector element.

[0013] In the first aspect, when viewed from the second direction, one region formed by the outlines of the plurality of light detection regions may have a shape corresponding to the outline shape of the side surface. In a configuration in which one region formed by the outlines of multiple photodetection regions has a shape corresponding to the outline shape of the side surface, it is not necessary to arrange the photodetection regions in locations on the semiconductor substrate that cannot receive scintillation light, thereby suppressing increases in dark count and capacitance in the photodetection regions. Therefore, this configuration reliably improves the time resolution and energy resolution of the radiation detector.

[0014] In the first aspect, the scintillator may have a plurality of independent portions corresponding to the plurality of photodetection regions, each of which may have a pair of opposing surfaces facing each other in the first direction and a connecting surface connecting the pair of opposing surfaces and facing the semiconductor substrate. In a configuration in which the scintillator has multiple independent sections corresponding to the multiple photodetection regions, the scintillation light generated in each section is confined within that section. The photodetection region corresponding to that section reliably detects the scintillation light generated within that section. Therefore, this configuration reliably achieves high energy resolution.

[0015] In the first aspect, the plurality of portions may be joined to one another. The structure in which multiple sections are bonded together improves the physical strength of the scintillator, and therefore this structure more reliably achieves high energy resolution.

[0016] In the first aspect, the light-reflecting element may further include a light-reflecting member. The light-reflecting member may be disposed between the plurality of portions. In a configuration in which a light reflecting member is disposed between multiple portions, the scintillation light generated in each portion is reliably confined within that portion. The light detection region corresponding to that portion more reliably detects the scintillation light generated within that portion. Therefore, this configuration more reliably achieves high energy resolution.

[0017] In the first aspect, at least one of the pair of opposing surfaces may be inclined with respect to the second direction. In a configuration in which at least one of the opposing surfaces is inclined with respect to the second direction, the scintillation light is more reliably incident on the coupling surface opposing the semiconductor substrate. Since the number of times the scintillation light is reflected by the opposing surface or the coupling surface is reduced and the return loss is also reduced, this configuration more reliably improves the amount of light received by the semiconductor photodetector element.

[0018] In the first aspect, of the pair of opposing surfaces, the opposing surface extending in the second direction may have a cross section that is triangular wave shaped. In a configuration in which the cross section of the opposing surface extending in the second direction D2 has a triangular wave shape, scintillation light is more reliably incident on the connecting surface opposing the semiconductor substrate. Since the number of times that the scintillation light is reflected by the opposing surface or the connecting surface is reduced and return attenuation is also reduced, this configuration further reliably improves the amount of light received by the semiconductor photodetector element.

[0019] In the above one aspect, of the pair of opposing surfaces, the opposing surface extending in the second direction may be a rough surface. In the configuration in which the facing surface extending in the second direction is rough, the scintillation light is more reliably incident on the connecting surface facing the semiconductor substrate. Since the number of times the scintillation light is reflected by the facing surface or the connecting surface is reduced and the return loss is also reduced, this configuration further reliably improves the amount of light received by the semiconductor photodetector element.

[0020] In the first aspect, the scintillator may have another connecting surface that connects the pair of opposing surfaces and is adjacent to the connecting surface, and that has a triangular wave-shaped cross section. In the case where the cross section of the other coupling surface is triangular wave shaped, the scintillation light is more reliably incident on the coupling surface facing the semiconductor substrate, and therefore this configuration more reliably improves the amount of light received by the semiconductor photodetector element.

[0021] In the first aspect, the scintillator may have another connecting surface that connects the pair of opposing surfaces and is a rough surface adjacent to the connecting surface. In the configuration in which the other coupling surface is rough, the scintillation light is more reliably incident on the coupling surface facing the semiconductor substrate, and therefore this configuration more reliably improves the amount of light received by the semiconductor photodetector element.

[0022] In the first aspect, when viewed from the second direction, each of the plurality of photodetection regions may have a contour shape that corresponds to the contour shape of the coupling surface of a corresponding one of the plurality of portions that faces the semiconductor substrate. In a configuration in which the photodetection region has a contour shape corresponding to the contour shape of the coupling surface, the photodetection region does not need to be disposed in a portion of the semiconductor substrate that cannot receive scintillation light, thereby suppressing increases in dark count and capacitance in the photodetection region, thereby reliably improving the time resolution and energy resolution of the radiation detector.

[0023] In the first aspect, the scintillator may have a rectangular or triangular shape when viewed from the first direction. In a configuration in which the scintillator has a rectangular or triangular shape, scintillation light is reliably incident on the surface facing the semiconductor substrate, thereby reliably improving the amount of light received by the semiconductor photodetector element.

[0024] In the first aspect, the plurality of photodetection regions may include a first photodetection region and a second photodetection region that is closer to the second portion than the first photodetection region. A width of a conductor electrically connecting the first electrode corresponding to the first photodetection region to the first photodetection region may be larger than a width of a conductor electrically connecting the first electrode corresponding to the second photodetection region to the second photodetection region. In a configuration in which the width of the conductor electrically connecting the first electrode corresponding to the first photodetection region to the first photodetection region is larger than the width of the conductor electrically connecting the first electrode corresponding to the second photodetection region to the second photodetection region, the difference in electrical resistance is reduced. The length of the conductor electrically connecting the first electrode corresponding to the first photodetection region to the first photodetection region is larger than the length of the conductor electrically connecting the first electrode corresponding to the second photodetection region to the second photodetection region. The longer the conductor, the higher the electrical resistance of the conductor. Therefore, in a configuration in which the width of the longer conductor is larger than the width of the shorter conductor, the difference in electrical resistance between the longer conductor and the shorter conductor is reduced. Therefore, this configuration more reliably improves the time resolution and energy resolution of the radiation detector.

[0025] In the first aspect, the device may further include a base disposed so that the semiconductor substrate is located between the base and the scintillator. The base may have a third portion covered with the semiconductor substrate and a fourth portion aligned with the third portion in the first direction and exposed from the semiconductor substrate. The fourth portion may include a first terminal and a second terminal disposed on the same side of the semiconductor substrate as the scintillator. The first terminal may be electrically connected to the first electrode by a first wire, and the second terminal may be electrically connected to the second electrode by a second wire. In the configuration including the base, the mechanical strength of the radiation detector is reinforced, and therefore, this configuration reliably realizes a radiation detector with reinforced mechanical strength.

[0026] In the first aspect, the first wire and the second wire may be covered with a resin. In the configuration in which the first wire and the second wire are covered with resin, the resin protects the first and second wires, making them less susceptible to damage, and therefore, this configuration suppresses deterioration of the electrical connection between the first and second terminals and the first and second electrodes.

[0027] In the first aspect, the light-emitting device may further include a light reflector arranged such that the semiconductor substrate is located between the light reflector and the scintillator. In a configuration including a light reflector, when one radiation detector is lined up with another radiation detector in the second direction, the light reflector of the one radiation detector improves the reflectivity of scintillation light on the other side surface that faces the side surface of the other radiation detector in the second direction. The other side surface of the other radiation detector has high reflectivity for scintillation light even in a configuration in which a light reflector is not provided. Therefore, this configuration simplifies the configuration of the radiation detector.

[0028] In the first aspect, the light reflector may have a thickness of 0.05 to 100 μm. In a configuration in which the thickness of the light reflector is within the above range, the reflectance of the scintillation light from the other side surface is reliably improved, and therefore this configuration reliably simplifies the configuration of the radiation detector.

[0029] In the first aspect, the wiring member may be disposed on the same side of the semiconductor substrate as the scintillator. In a configuration in which the wiring member is disposed on the same side of the semiconductor substrate as the scintillator, it is not necessary to prepare a new substrate for connecting the wiring member to the first and second electrodes by die bonding, for example, and therefore this configuration more reliably simplifies the configuration of the radiation detector.

[0030] In the first aspect, the wiring member and the semiconductor substrate may be flexible. The flexibility of the wiring member may be greater than the flexibility of the semiconductor substrate. In a configuration in which the flexibility of the wiring member is greater than the flexibility of the semiconductor substrate, vibrations are less likely to be transmitted from the wiring member to the semiconductor substrate. Forces from the wiring member are less likely to be applied to the semiconductor substrate, and the semiconductor substrate is less likely to be physically damaged. Therefore, this configuration reliably maintains the mechanical strength of the radiation detector.

[0031] A radiation detector according to a second aspect includes a scintillator having a rectangular shape when viewed from a first direction and including a pair of end faces facing each other in the first direction, a first side face connecting the pair of end faces, and a second side face connecting the pair of end faces and adjacent to the side face, a first semiconductor photodetector element having a first semiconductor substrate arranged to face the first side face, a second semiconductor photodetector element having a second semiconductor substrate arranged to face the second side face, a first wiring member electrically connected to the first semiconductor photodetector element, and a second wiring member electrically connected to the second semiconductor photodetector element. The length of the scintillator in the first direction is greater than the length of the scintillator in a second direction perpendicular to the first side face and the length of the scintillator in a third direction perpendicular to the second side face. The length of the first side face in the first direction is greater than the width of the first side face in the third direction. The length of the second side face in the first direction is greater than the width of the second side face in the second direction. The first semiconductor substrate and the second semiconductor substrate have a first portion covered by either a corresponding first side surface or a second side surface and including a plurality of photodetection regions, and a second portion aligned with the first portion in a first direction and exposed from either the corresponding first side surface or the second side surface. The plurality of photodetection regions are aligned in the first direction and each include at least one avalanche photodiode operating in Geiger mode and at least one quenching resistor electrically connected in series with one of the anode and cathode of a corresponding one of the at least one avalanche photodiodes. The second portion includes a plurality of first electrodes electrically connected to at least one quenching resistor included in a corresponding one of the plurality of photodetection regions, and a second electrode electrically connected to the other of the anode and cathode of each avalanche photodiode. The first wiring member and the second wiring member include a plurality of conductors electrically connected to corresponding one of the plurality of first electrodes and a conductor connected to the second electrode.

[0032] According to the second aspect, the radiation detector includes a scintillator that is long in a first direction and a semiconductor photodetector element that is arranged on a side of the scintillator. The semiconductor photodetector element not only detects scintillation light that is directly incident on the side surface on which the semiconductor photodetector element is arranged, but also detects scintillation light that is incident on the side surface after being reflected by another side surface that faces the side surface on which the semiconductor photodetector element is arranged. Because the length of the scintillator in the second direction is shorter than the length of the scintillator in the first direction, the scintillation light that is directly incident on the side surface and the scintillation light that is incident on the side surface after being reflected by the other side surface are detected by the semiconductor photodetector element with a small time difference. Therefore, the second aspect achieves high time resolution. According to the second aspect, even if the angle of incidence of scintillation light on the first side surface exceeds the critical angle at the first side surface and the scintillation light is not detected by the first semiconductor photodetector element arranged on the first side surface, the scintillation light is detected by the second semiconductor photodetector element arranged on the second side surface adjacent to the first side surface. Therefore, the second aspect realizes a radiation detector having high time resolution and reliably improves the amount of scintillation light received by the first and second semiconductor photodetector elements. According to the second aspect, the radiation detector includes a semiconductor photodetector element having a plurality of photodetection regions arranged in a first direction. For example, the distance in the first direction between the point of generation of scintillation light and one end face of the scintillator can be determined from the position of the photodetection region that detects the most scintillation light among the plurality of photodetection regions. As a result, the magnitude of the energy of the radiation incident on the scintillator can be accurately measured. Therefore, the second aspect achieves high energy resolution.

[0033] In the second aspect, at least one of the pair of end faces may be inclined with respect to the second direction. In a configuration in which at least one of the end faces is inclined with respect to the second direction, the scintillation light is more reliably incident on the side faces facing the first and second semiconductor substrates. Since the number of times the scintillation light is reflected by the end face or side face is reduced and return attenuation is also reduced, this configuration more reliably improves the amount of light received by the first and second semiconductor photodetector elements.

[0034] In the second aspect, of the pair of end faces, the end face extending in the second direction may have a cross section with a triangular wave shape. In a configuration in which the cross section of the end face extending in the second direction has a triangular wave shape, the scintillation light is more reliably incident on the side face facing the first and second semiconductor substrates. Since the number of times the scintillation light is reflected by the end face or side face is reduced and return attenuation is also reduced, this configuration more reliably improves the amount of light received by the first and second semiconductor photodetector elements.

[0035] In the second aspect, the end face of the pair of end faces that extends in the second direction may be a rough surface. In a configuration in which the end faces extending in the second direction are roughened, the scintillation light is more reliably incident on the side faces facing the first and second semiconductor substrates. Since the number of times the scintillation light is reflected by the end faces or side faces is reduced and return attenuation is also reduced, this configuration more reliably improves the amount of light received by the first and second semiconductor photodetector elements.

[0036] In the second aspect, when viewed from the second direction, one region formed by the outlines of the plurality of photodetection regions may have a shape corresponding to the outline shape of the first side surface. When viewed from the third direction, one region formed by the outlines of the plurality of photodetection regions may have a shape corresponding to the outline shape of the second side surface. In a configuration in which one region formed by the outlines of the multiple photodetection regions has a shape corresponding to the outline shapes of the first and second side surfaces, the photodetection regions do not need to be disposed in locations on the first and second semiconductor substrates that cannot receive scintillation light, thereby suppressing increases in dark count and capacitance in the photodetection regions. Therefore, this configuration reliably improves the time resolution and energy resolution of the first and second semiconductor photodetector elements.

[0037] In the second aspect, the scintillator may have a plurality of independent portions corresponding to the plurality of photodetection regions, each of the plurality of portions having a pair of opposing surfaces facing each other in the first direction, a first connecting surface connecting the pair of opposing surfaces and facing the first semiconductor substrate, and a second connecting surface connecting the pair of opposing surfaces, facing the second semiconductor substrate, and adjacent to the first connecting surface. In a configuration in which the scintillator has multiple independent sections corresponding to the multiple photodetection regions, the scintillation light generated in each section is confined within that section. The photodetection region corresponding to that section reliably detects the scintillation light generated within that section. Therefore, this configuration reliably achieves high energy resolution.

[0038] In the second aspect, the plurality of portions may be joined to one another. The structure in which multiple sections are bonded together improves the physical strength of the scintillator, and therefore this structure more reliably achieves high energy resolution.

[0039] In the second aspect, the light-reflecting element may further comprise a light-reflecting member. The light-reflecting member may be disposed between the plurality of portions. In a configuration in which a light reflecting member is disposed between multiple portions, the scintillation light generated in each portion is reliably confined within that portion. The light detection region corresponding to that portion more reliably detects the scintillation light generated within that portion. Therefore, this configuration more reliably achieves high energy resolution.

[0040] In the second aspect, at least one of the pair of opposing surfaces may be inclined with respect to the second direction. In a configuration in which at least one of the opposing surfaces is inclined with respect to the second direction, the scintillation light is more reliably incident on the connecting surfaces that face the first and second semiconductor substrates. Since the number of times that the scintillation light is reflected by the opposing surfaces or the connecting surfaces is reduced and the return attenuation is also reduced, this configuration more reliably improves the amount of light received by the first and second semiconductor photodetector elements.

[0041] In the second aspect, of the pair of opposing surfaces, the opposing surface extending in the second direction may have a cross section that is triangular wave shaped. In a configuration in which the cross section of the opposing surface extending in the second direction has a triangular wave shape, scintillation light is more reliably incident on the connecting surface opposing the first and second semiconductor substrates. Since the number of times that the scintillation light is reflected by the opposing surface or the connecting surface is reduced and return attenuation is also reduced, this configuration further reliably improves the amount of light received by the first and second semiconductor photodetector elements.

[0042] In the second aspect, of the pair of opposing surfaces, the opposing surface extending in the second direction may be a rough surface. In a configuration in which the facing surfaces extending in the second direction are roughened, the scintillation light is more reliably incident on the connecting surfaces facing the first and second semiconductor substrates. Since the number of times the scintillation light is reflected by the facing surfaces or the connecting surfaces is reduced and return attenuation is also reduced, this configuration further reliably improves the amount of light received by the first and second semiconductor photodetector elements.

[0043] In the second aspect, when viewed from the second direction, each of the plurality of photodetection regions may have a contour shape corresponding to the contour shape of the first coupling surface of a corresponding one of the plurality of portions that faces the first semiconductor substrate. When viewed from the third direction, each of the plurality of photodetection regions may have a contour shape corresponding to the contour shape of the second coupling surface of a corresponding one of the plurality of portions that faces the second semiconductor substrate. In a configuration in which each of the plurality of photodetection regions has a contour shape corresponding to the contour shape of the first and second coupling surfaces of the corresponding portion of the plurality of portions that face the first and second semiconductor substrates, the photodetection regions do not need to be disposed in portions of the first and second semiconductor substrates that cannot receive scintillation light, thereby suppressing increases in dark count and capacitance in the photodetection regions. Therefore, this configuration reliably improves the time resolution and energy resolution of the first and second semiconductor photodetector elements.

[0044] In the second aspect, the plurality of photodetection regions may include a first photodetection region and a second photodetection region that is closer to the second portion than the first photodetection region. A width of a conductor electrically connecting the first electrode corresponding to the first photodetection region to the first photodetection region may be larger than a width of a conductor electrically connecting the first electrode corresponding to the second photodetection region to the second photodetection region. In a configuration in which the width of the conductor electrically connecting the first electrode corresponding to the first photodetection region to the first photodetection region is larger than the width of the conductor electrically connecting the first electrode corresponding to the second photodetection region to the second photodetection region, the difference in electrical resistance is reduced. The length of the conductor electrically connecting the first electrode corresponding to the first photodetection region to the first photodetection region is larger than the length of the conductor electrically connecting the first electrode corresponding to the second photodetection region to the second photodetection region. The longer the conductor, the higher the electrical resistance of the conductor. Therefore, in a configuration in which the width of the longer conductor is larger than the width of the shorter conductor, the difference in electrical resistance between the longer conductor and the shorter conductor is reduced. Therefore, this configuration more reliably improves the time resolution and energy resolution of the radiation detector.

[0045] The second aspect may further include a first substrate arranged such that the first semiconductor substrate is located between the first substrate and the scintillator, and a second substrate arranged such that the second semiconductor substrate is located between the first substrate and the scintillator. The first substrate and the second substrate may each have a third portion covered by the first semiconductor substrate and the second semiconductor substrate, and a fourth portion aligned with the third portion in the first direction and exposed from the first semiconductor substrate and the second semiconductor substrate. Each fourth portion may include a first terminal and a second terminal arranged on the same side as the scintillator with respect to the corresponding first semiconductor substrate or second semiconductor substrate. The first terminal may be electrically connected to the first electrode by a first wire, and the second terminal may be electrically connected to the second electrode by a second wire. In the configuration including the first and second bases, the mechanical strength of the radiation detector is reinforced, and therefore, this configuration reliably realizes a radiation detector with reinforced mechanical strength.

[0046] In the second aspect, the first wire and the second wire may be covered with a resin. In the configuration in which the first wire and the second wire are covered with resin, the resin protects the first and second wires, making them less susceptible to damage, and therefore, this configuration suppresses deterioration of the electrical connection between the first and second terminals and the first and second electrodes.

[0047] The second aspect may further include a first light reflector arranged so that the first semiconductor substrate is located between the first light reflector and the scintillator, and a second light reflector arranged so that the second semiconductor substrate is located between the scintillator and the first light reflector. In a configuration including a first light reflector and a second light reflector, the first light reflector improves the reflectivity of scintillation light at the second side surface of the radiation detector adjacent in the second direction. The side surfaces of the other radiation detectors have high reflectivity for scintillation light even in a configuration in which the first light reflector is not provided. The second light reflector improves the reflectivity of scintillation light at the side surfaces of the radiation detectors adjacent in the third direction. The side surfaces of the other radiation detectors have high reflectivity for scintillation light even in a configuration in which the second light reflector is not provided. Therefore, this configuration reliably simplifies the configuration of the radiation detector.

[0048] In the second aspect, the first light reflector and the second light reflector may each have a thickness of 0.05 to 100 μm. In a configuration in which the thicknesses of the first and second light reflectors are within the above range, the reflectance of scintillation light from the other side surface is reliably improved, and therefore this configuration reliably simplifies the configuration of the radiation detector.

[0049] In the second aspect, the first wiring member may be disposed on the same side of the first semiconductor substrate as the scintillator, and the second wiring member may be disposed on the same side of the second semiconductor substrate as the scintillator. In a configuration in which the first and second wiring members are disposed on the same side of the first and second semiconductor substrates as the scintillator, there is no need to prepare a new substrate for connecting the first and second wiring members to the first and second electrodes, respectively, by die bonding, and therefore this configuration more reliably simplifies the configuration of the radiation detector.

[0050] In the second aspect, the first wiring member, the second wiring member, the first semiconductor substrate, and the second semiconductor substrate may be flexible. The flexibility of the first wiring member may be greater than the flexibility of the first semiconductor substrate. The flexibility of the second wiring member may be greater than the flexibility of the second semiconductor substrate. In a configuration in which the flexibility of the first and second wiring members is greater than the flexibility of the first and second semiconductor substrates, respectively, vibrations are less likely to be transmitted from the first and second wiring members to the first and second semiconductor substrates. Forces from the first and second wiring members are less likely to be applied to the first and second semiconductor substrates, respectively, and the first and second semiconductor substrates are less likely to be physically damaged. Therefore, this configuration reliably maintains the mechanical strength of the radiation detector.

[0051] A radiation detector array according to a third aspect is a radiation detector array in which a plurality of radiation detectors are arranged two-dimensionally in a matrix when viewed from a first direction, each of the plurality of radiation detectors being the radiation detector according to the first aspect, and the semiconductor photodetector element of one radiation detector is aligned with the semiconductor photodetector element of another radiation detector adjacent to it in a direction parallel to the side surface.

[0052] According to the third aspect, a radiation detector array is realized in which radiation detectors having high time resolution and high energy resolution are arranged two-dimensionally in a matrix.

[0053] In the third aspect, the semiconductor photodetector elements adjacent to each other in a direction parallel to the side surfaces may be formed integrally with each other. In a configuration in which the semiconductor photodetector elements are integrally formed with one another, the process of forming the semiconductor photodetector elements is simplified when fabricating a radiation detector array in which a plurality of radiation detectors are two-dimensionally arranged in a matrix.

[0054] A radiation detector array according to a fourth aspect is a radiation detector array in which a plurality of radiation detectors are arranged two-dimensionally in a matrix when viewed from a first direction, and each of the plurality of radiation detectors is the radiation detector according to the second aspect, and the first semiconductor photodetection element of one radiation detector is aligned with the first semiconductor photodetection element of another radiation detector adjacent to it in the third direction, and the second semiconductor photodetection element of one radiation detector is aligned with the second semiconductor photodetection element of yet another radiation detector adjacent to it in the second direction.

[0055] According to the fourth aspect, a radiation detector array is realized in which radiation detectors having high time resolution and high energy resolution are arranged two-dimensionally in a matrix.

[0056] In the fourth aspect, the first semiconductor photodetector elements adjacent to each other in the third direction may be formed integrally with each other. In a configuration in which each first semiconductor photodetector element is formed integrally with another, the process of forming the first semiconductor photodetector elements is simplified when producing a radiation detector array in which a plurality of radiation detectors are arranged two-dimensionally in a matrix.

[0057] In the fourth aspect, the second semiconductor photodetector elements adjacent to each other in the second direction may be formed integrally with each other. In a configuration in which each second semiconductor photodetector element is formed integrally with another, the process of forming the second semiconductor photodetector elements is simplified when producing a radiation detector array in which a plurality of radiation detectors are arranged two-dimensionally in a matrix. [Effects of the Invention]

[0058] The first and second aspects of the present invention provide a radiation detector having high time resolution and high energy resolution, while the third and fourth aspects of the present invention provide a radiation detector array including radiation detectors having high time resolution and high energy resolution. [Brief explanation of the drawings]

[0059] [Figure 1] FIG. 1 is a perspective view showing a radiation detector according to the first embodiment. [Figure 2] FIG. 2 is a plan view showing the semiconductor photodetector element. [Figure 3] FIG. 3 is a diagram showing an equivalent circuit of the photodetection region. [Figure 4] FIG. 4 is a perspective view showing the radiation detector according to the first embodiment. [Figure 5] FIG. 5 is a diagram showing the path of part of the scintillation light. [Figure 6]FIG. 6 is a diagram showing the path of part of the scintillation light. [Figure 7] FIG. 7 is a diagram showing the path of part of the scintillation light. [Figure 8] FIG. 8 is a diagram showing an example of the contour shape of another side surface. [Figure 9] FIG. 9 is a perspective view showing a radiation detector according to a first modified example of the first embodiment. [Figure 10] FIG. 10 is a diagram showing the path of part of the scintillation light. [Figure 11] FIG. 11 is a perspective view showing a radiation detector according to a second modified example of the first embodiment. [Figure 12] FIG. 12 is a perspective view showing a radiation detector according to a third modified example of the first embodiment. [Figure 13] FIG. 13 is a diagram showing the path of part of the scintillation light. [Figure 14] FIG. 14 is a perspective view showing a radiation detector according to a fourth modified example of the first embodiment. [Figure 15] FIG. 15 is a diagram showing the path of part of the scintillation light. [Figure 16] FIG. 16 is a perspective view showing a radiation detector according to a fifth modified example of the first embodiment. [Figure 17] FIG. 17 is a plan view showing the semiconductor photodetector element. [Figure 18] FIG. 18 is a perspective view showing a radiation detector according to a sixth modified example of the first embodiment. [Figure 19] FIG. 19 is a plan view showing the semiconductor photodetector element. [Figure 20] FIG. 20 is a perspective view showing a radiation detector according to a seventh modification of the first embodiment. [Figure 21] FIG. 21 is a plan view showing the semiconductor photodetector element. [Figure 22] FIG. 22 is a perspective view showing a radiation detector according to an eighth modified example of the first embodiment. [Figure 23] FIG. 23 is a diagram showing the path of part of the scintillation light. [Figure 24] FIG. 24 is a perspective view showing a radiation detector according to the second embodiment. [Figure 25] FIG. 25 is a diagram showing the path of part of the scintillation light. [Figure 26] FIG. 26 is a perspective view showing a radiation detector according to a first modified example of the second embodiment. [Figure 27] FIG. 27 is a perspective view showing a radiation detector according to a second modified example of the second embodiment. [Figure 28] FIG. 28 is a perspective view showing a radiation detector according to a third modified example of the second embodiment. [Figure 29] FIG. 29 is a perspective view showing a radiation detector according to a fourth modified example of the second embodiment. [Figure 30] FIG. 30 is a perspective view showing a radiation detector array according to the third embodiment. [Figure 31] FIG. 31 is a perspective view showing a radiation detector array according to the fourth embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0060] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0023] The present invention will be described in detail with reference to the accompanying drawings. In the description, the same elements or elements having the same functions will be denoted by the same reference numerals, and redundant description will be omitted.

[0061] (First embodiment) The configuration of a radiation detector RD1 according to a first embodiment will be described with reference to Figs. 1 to 4. Fig. 1 is a perspective view showing the radiation detector according to the first embodiment. Fig. 2 is a plan view showing a semiconductor photodetector element. Fig. 3 is a diagram showing an equivalent circuit of the photodetection region. Fig. 4 is a perspective view showing the radiation detector according to the first embodiment.

[0062] 1, radiation detector RD1 includes a scintillator 1, a semiconductor photodetector element 10, and a wiring member 30. The scintillator 1 generates scintillation light (fluorescence) upon receiving incident radiation. The semiconductor photodetector element 10 detects the scintillation light generated by the scintillator 1. The semiconductor photodetector element 10 has a semiconductor substrate 11, and is electrically connected to the wiring member 30.

[0063] The scintillator 1 has a pair of end faces 1a and 1b facing each other, a pair of side faces 1c and 1d facing each other, and a pair of side faces 1e and 1f facing each other. The end faces 1a and 1b, the side faces 1c and 1d, and the side faces 1e and 1f constitute the outer surface of the scintillator 1. The end faces 1a and 1b face each other in a first direction D1. The end faces 1a and 1b define both ends of the scintillator 1 in the first direction D1. The side faces 1c and 1d face each other in a second direction D2 intersecting the first direction D1. In this embodiment, the second direction D2 coincides with a direction perpendicular to the side face 1c. The side faces 1c and 1d define both ends of the scintillator 1 in the second direction D2. The side faces 1e and 1f face each other in a third direction D3 intersecting the first direction D1 and the second direction D2. In this embodiment, the first direction D1, the second direction D2, and the third direction D3 are perpendicular to each other. Sides 1e and 1f define both ends of scintillator 1 in third direction D3. The length of scintillator 1 in first direction D1 is greater than the length of scintillator 1 in second direction D2 perpendicular to side 1c. First direction D1 is the longitudinal direction of scintillator 1.

[0064] End face 1a and end face 1b extend in the second direction D2 to connect side face 1c and side face 1d. End face 1a and end face 1b extend in the third direction D3 to connect side face 1e and side face 1f. Side face 1c and side face 1d extend in the first direction D1 to connect end face 1a and end face 1b. Side face 1c and side face 1d extend in the third direction D3 to connect side face 1e and side face 1f. Side face 1e and side face 1f extend in the first direction D1 to connect end face 1a and end face 1b. Side face 1e and side face 1f extend in the second direction D2 to connect side face 1c and side face 1d. Side face 1e and side face 1f are adjacent to side face 1c. In this embodiment, the length of side face 1c in the first direction D1 is greater than the width of side face 1c in the third direction D3.

[0065] The length of the scintillator 1 in the first direction D1 is, for example, about 20 mm, the length of the scintillator 1 in the second direction D2 is, for example, about 4 mm, and the length of the scintillator 1 in the third direction D3 is, for example, about 4 mm.

[0066] In this embodiment, the end faces 1a, 1b, the side faces 1c, 1d, and the side faces 1e, 1f have a rectangular shape when viewed from a direction perpendicular to these faces. The scintillator 1 has a rectangular shape when viewed from the second direction D2 and the third direction D3. The scintillator 1 also has a rectangular shape when viewed from the first direction D1. In this embodiment, the scintillator 1 has a rectangular parallelepiped shape. In this specification, "rectangular shape" includes, for example, a shape in which each corner is chamfered and a shape in which each corner is rounded. In this specification, "rectangular shape" includes a rectangular parallelepiped shape in which the corners and ridges are chamfered and a rectangular parallelepiped shape in which the corners and ridges are rounded.

[0067] The scintillator 1 includes, for example, a crystalline scintillator, a ceramic scintillator, or a plastic scintillator. Crystalline scintillators include, for example, CsI, NaI, LaBr3, cerium-doped lutetium yttrium orthosilicate (LYSO(Ce)), gadolinium aluminum gallium garnet (GAGG), lutetium oxyorthosilicate (LSO), bismuth germanate (BGO), or ruthenium aluminum garnet (LuAG). Ceramic scintillators include, for example, a sintered body of an inorganic phosphor. Plastic scintillators include, for example, polyethylene terephthalate (PET).

[0068] As shown in FIGS. 1 and 2, the semiconductor substrate 11 is disposed so as to face the side surface 1c. The semiconductor substrate 11 is disposed on the side surface 1c, for example, via an adhesive. The semiconductor substrate 11 includes, for example, Si. The semiconductor substrate 11 has a first portion 21 and a second portion 22. In this embodiment, the first portion 21 is covered by the side surface 1c. The second portion 22 is aligned with the first portion 21 in the first direction D1 and is exposed from the side surface 1c.

[0069] As shown in FIGS. 2 and 3 , a plurality of photodetection regions 23a, 23b, 23c, and 23d are arranged in the first portion 21. The photodetection regions 23a, 23b, 23c, and 23d are aligned in the first direction D1. In this embodiment, four photodetection regions 23a, 23b, 23c, and 23d are arranged. Each of the photodetection regions 23a, 23b, 23c, and 23d includes at least one avalanche photodiode 12 and at least one quenching resistor 13. In the example shown in FIG. 2 , each of the photodetection regions 23a, 23b, 23c, and 23d includes a plurality of avalanche photodiodes 12 and a plurality of quenching resistors 13. The avalanche photodiode 12 receives scintillation light and generates photoelectrons by photoelectric conversion. The first portion 21 includes, for example, four conductive wires 14a, 14b, 14c, 14d and a conductive wire 14e. The conductive wires 14a, 14b, 14c, and 14d form a signal readout wiring pattern that is patterned in a grid when viewed from the second direction D2. Each grid of the conductive wires 14a, 14b, 14c, and 14d surrounds one photodetector 15. One photodetector 15 includes one avalanche photodiode 12 and one quenching resistor 13 electrically connected in series with the corresponding avalanche photodiode 12. The first portion 21 includes a plurality of photodetectors 15, which are arranged two-dimensionally in a matrix. In the example shown in FIG. 2, the photodetection regions 23a, 23b, 23c, and 23d are in contact with each other. In practice, the photodetection regions 23 a, 23 b, 23 c, and 23 d may be adjacent to each other or spaced apart from each other. Each of the photodetection regions 23 a, 23 b, 23 c, and 23 d may include one avalanche photodiode 12 and one quenching resistor 13.

[0070] At least one quenching resistor 13 is electrically connected in series with one of the anode and cathode of a corresponding one of at least one avalanche photodiode 12. The avalanche photodiode 12 has a contact electrode 16 electrically connected to one of the anode and cathode, and one end of the quenching resistor 13 is electrically connected in series with the contact electrode 16. The other end of each quenching resistor 13 is electrically connected in series with conductors 14a, 14b, 14c, and 14d that form a wiring pattern. The conductors 14a, 14b, 14c, and 14d are each electrically connected in parallel with the multiple quenching resistors 13. The conductor 14e electrically connects the other of the anodes and cathodes of the multiple avalanche photodiodes 12 in parallel.

[0071] The second portion 22 includes a plurality of first electrodes 17a, 17b, 17c, and 17d and a second electrode 18. The first electrodes 17a, 17b, 17c, and 17d electrically connect at least one quenching resistor 13 included in a corresponding one of the plurality of photodetection regions 23a, 23b, 23c, and 23d via conductive wires 14a, 14b, 14c, and 14d, respectively. In the example shown in FIG. 2, the first electrodes 17a, 17b, 17c, and 17d electrically connect in parallel a plurality of quenching resistors 13 included in a corresponding one of the plurality of photodetection regions 23a, 23b, 23c, and 23d via conductive wires 14a, 14b, 14c, and 14d, respectively. The first electrode 17a is connected to the photodetection region 23a via conductive wire 14a. The first electrode 17b is connected to the photodetection region 23b via the conductor 14b. The first electrode 17c is connected to the photodetection region 23c via the conductor 14c. The first electrode 17d is connected to the photodetection region 23d via the conductor 14d. In a configuration in which the photodetection regions 23a, 23b, 23c, and 23d each include one quenching resistor 13, the first electrodes 17a, 17b, 17c, and 17d electrically connect in series with one quenching resistor 13 included in the photodetection regions 23a, 23b, 23c, and 23d via the conductors 14a, 14b, 14c, and 14d, respectively. The second electrode 18 is electrically connected to the other of the anode and the cathode of at least one avalanche photodiode 12 via the conductor 14e. In the example shown in Fig. 2, the second electrode 18 electrically connects the other of the anode and the cathode of the multiple avalanche photodiodes 12 in parallel via the conductor 14e. In a configuration in which the photodetection regions 23a, 23b, 23c, and 23d each include one avalanche photodiode 12, the second electrode 18 electrically connects the other of the anode and the cathode of one avalanche photodiode 12 included in the photodetection regions 23a, 23b, 23c, and 23d in parallel via the conductor 14e.

[0072] The first electrodes 17a, 17b, 17c, 17d and the second electrode 18 include, for example, aluminum or an aluminum composite (AlSi, AlCu, AlSiCu, etc.) The first electrodes 17a, 17b, 17c, 17d and the second electrode 18 are formed by, for example, a plating method, a vapor deposition method, or a sputtering method.

[0073] The electrical resistivity of the quenching resistor 13 is greater than the electrical resistivity of the first electrodes 17a, 17b, 17c, and 17d and the second electrode 18. The quenching resistor 13 includes, for example, polysilicon. The material of the quenching resistor 13 may include, for example, SiCr, NiCr, or FeCr. The quenching resistor 13 is formed by, for example, a chemical vapor deposition (CVD) method or a sputtering method.

[0074] In this embodiment, for example, at least one quenching resistor 13 electrically connects the anode of a corresponding one of the at least one avalanche photodiode 12. In this case, the second electrode 18 is electrically connected to the cathodes of the multiple avalanche photodiodes 12. At least one quenching resistor 13 may electrically connect the cathode of a corresponding one of the at least one avalanche photodiode 12. In this case, the second electrode 18 electrically connects the anode of the at least one avalanche photodiode 12.

[0075] Each avalanche photodiode 12 operates in Geiger mode. In Geiger mode, a reverse voltage (reverse bias voltage) greater than the breakdown voltage of the avalanche photodiode 12 is applied to the avalanche photodiode 12. For example, a potential V1 is applied to the anode of the avalanche photodiode 12, and a potential V2 that is positive with respect to the potential V1 is applied to the cathode of the avalanche photodiode 12. The polarities of these potentials are relative, and for example, one of the potentials may be the ground potential. The photodetector units 15 are connected in parallel.

[0076] Each avalanche photodiode 12 may be a so-called reach-through type avalanche photodiode or a so-called reverse type avalanche photodiode. The reach-through type avalanche photodiode 12 is used, for example, when the scintillation light is long-wavelength light. The reverse type avalanche photodiode 12 is used, for example, when the scintillation light is short-wavelength light. These reach-through type or reverse type avalanche photodiodes 12 operate in Geiger mode. The radiation detector RD1 may be equipped with an avalanche photodiode 12 that operates in linear mode. The avalanche photodiode 12 that operates in linear mode may also be a so-called reach-through type avalanche photodiode or a so-called reverse type avalanche photodiode.

[0077] The semiconductor substrate 11 is provided with, for example, conductive wires 14a, 14b, 14c, 14d and 14e, first electrodes 17a, 17b, 17c, 17d connected to the conductive wires 14a, 14b, 14c, 14d, respectively, and a second electrode 18 connected to the conductive wire 14e. The semiconductor substrate 11 is provided with, for example, an insulating layer 19 on the conductive wires 14a, 14b, 14c, 14d and 14e. The insulating layer 19 extends between a first portion 21 and a second portion 22. In the second portion 22, the first electrodes 17a, 17b, 17c, 17d and the conductive wires 14a, 14b, 14c, 14d are insulated from the second electrode 18 and the conductive wire 14e by the insulating layer 19. In the first portion 21, the insulating layer 19 is formed on the plurality of photodetectors 15. The insulating layer 19 includes, for example, SiO2 or SiN. The insulating layer 19 is formed by, for example, a thermal oxidation method, a sputtering method, or a CVD method.

[0078] The wiring member 30 is disposed on the same side of the semiconductor substrate 11 as the scintillator 1. The wiring member 30 includes conductors 31a, 31b, 31c, and 31d and a conductor 32. The conductors 31a, 31b, 31c, and 31d are electrically connected to the first electrodes 17a, 17b, 17c, and 17d, and the conductor 32 is electrically connected to the second electrode 18. The conductors 31a, 31b, 31c, and 31d are electrically connected to the first electrodes 17a, 17b, 17c, and 17d via conductive bumps 33. The conductor 32 is connected to the second electrode 18 via the conductive bumps 33. The conductive bumps 33 include, for example, solder, anisotropic conductive film (ACF), or anisotropic conductive paste (ACP). The solder includes, for example, Sn—Ag—Cu solder. The conductive bumps 33a may include, for example, Au bumps, Ni bumps, or Cu bumps.

[0079] In this embodiment, a potential V1 is applied to the anode of the avalanche photodiode 12 via the conductors 31a, 31b, 31c, and 31d, and a potential V2 is applied to the cathode of the avalanche photodiode 12 via the conductor 32. The potential V1 may be applied to the cathode of the avalanche photodiode 12 via the conductor 32, and the potential V2 may be applied to the anode of the avalanche photodiode 12 via the conductors 31a, 31b, 31c, and 31d. In FIG. 3 , only the conductor 31a is illustrated. The conductors 31a, 31b, 31c, and 31d and the conductor 32 may include, for example, Al, Cu, Cu / Ni / Au, or Cu / Ni / Pd / Au. The conductors 31a, 31b, 31c, and 31d and the conductor 32 may be formed by, for example, a sputtering method or a plating method. The wiring member 30 and the light detection regions 23a, 23b, 23c, and 23d are flexible, and the flexibility of the wiring member 30 is greater than the flexibility of the light detection regions 23.

[0080] When viewed from the second direction D2, one region formed by the multiple photodetection regions 23a, 23b, 23c, and 23d follows the contour of the side surface 1c. When viewed from the second direction D2, the multiple edges forming the contour of each photodetection region 23a, 23b, 23c, and 23d follow corresponding edges among the multiple edges forming the contour of the side surface 1c. When viewed from the second direction D2, one region formed by the contours of the multiple photodetection regions 23a, 23b, 23c, and 23d has a shape corresponding to the contour shape of the side surface 1c. When viewed from the second direction D2, each photodetector 15 is arranged such that one region formed by the photodetection regions 23a, 23b, 23c, and 23d has a contour shape corresponding to the contour shape of the side surface 1c. When viewed from the second direction D2, each photodetection region 23a, 23b, 23c, and 23d has a contour shape corresponding to the contour shape of the side surface 1c.

[0081] 2, in the photodetection regions 23a, 23b, and 23c, the photodetectors 15 are arranged in three rows in each direction in the first direction D1 and three rows in each direction in the third direction D3. The photodetection region 23a includes a total of nine photodetectors 15. In the photodetection region 23d, the photodetectors 15 are arranged in five rows in each direction in the first direction D1 and three rows in each direction in the third direction D3. The photodetection region 23d includes a total of 15 photodetectors 15.

[0082] The photodetection regions 23a, 23b, 23c, and 23d are arranged, for example, in the first direction D1. In this embodiment, the photodetection regions 23a, 23b, 23c, and 23d are arranged in this order. The photodetection region 23d is closer to the second portion than the photodetection regions 23a, 23b, and 23c. The photodetection region 23c is closer to the second portion than the photodetection regions 23a and 23b. The photodetection region 23b is closer to the second portion than the photodetection region 23a. In this embodiment, the width of the conductive wire 14a is larger than the widths of the conductive wires 14b, 14c, and 14d. The width of the conductive wire 14b is larger than the widths of the conductive wires 14c and 14d. The width of the conductive wire 14c is larger than the width of the conductive wire 14d. When viewed from the second direction D2, for example, the conductive wires 14a and 14b and 14c extend between both ends of the semiconductor substrate 11 in the third direction D3 and the photodetection regions 23a, 23b, 23c, and 23d. When viewed from the second direction D2, the conductive wire 14d is disposed, for example, between the conductive wires 14a and 14b and 14c. The conductive wires 14a, 14b, 14c, and 14d extend in the first direction D1. The widths of the conductive wires 14a, 14b, 14c, and 14d are widths in a direction perpendicular to the extension direction of the conductive wires 14a, 14b, 14c, and 14d. The widths of the conductive wires 14a, 14b, 14c, and 14d are widths in the third direction D3. For example, when the photodetection region 23a constitutes a first photodetection region, the photodetection region 23d constitutes a second photodetection region.

[0083] 4, the radiation detector RD1 includes, for example, a base 40. The base 40 is disposed such that the semiconductor substrate 11 is located between the base 40 and the scintillator 1. The base 40 has a third portion 51 and a fourth portion 52. The third portion 51 is covered with the semiconductor substrate 11. The fourth portion 52 is aligned with the third portion 51 in the first direction D1 and is exposed from the semiconductor substrate 11.

[0084] The fourth portion 52 includes first terminals 41a, 41b, 41c, and 41d and a second terminal 42. The first terminals 41a, 41b, 41c, and 41d and the second terminal 42 are arranged, for example, on the same side as the scintillator 1 with respect to the semiconductor substrate 11. The first terminals 41a, 41b, 41c, and 41d are electrically connected to the first electrodes 17a, 17b, 17c, and 17d by first wires 43, and the second terminal 42 is electrically connected to the second electrode 18 by a second wire 44.

[0085] The radiation detector RD1 includes, for example, a resin 45. The first wire 43 and the second wire 44 are covered with the resin 45. The resin 45 covers the first wire 43 and the second wire 44 individually, or covers both the first wire 43 and the second wire 44. When the resin 45 covers the first wire 43 and the second wire 44 individually, the resins 45 may be spaced apart from each other or connected to each other. In this specification, "the resin 45 covers the first wire 43" also includes covering the connection points between the first terminals 41a, 41b, 41c, and 41d and the first wire 43, and the connection points between the first electrodes 17a, 17b, 17c, and 17d and the first wire 43. Furthermore, "the resin 45 covers the second wire 44" also includes covering the connection points between the second terminal 42 and the second wire 44, and the connection points between the second electrode 18 and the second wire 44. The wiring member 30 is electrically connected to the first electrodes 17a, 17b, 17c, and 17d and the second electrode 18 via conductive bumps 46.

[0086] The radiation detector RD1 includes a light reflector 47. The light reflector 47 is disposed such that the semiconductor substrate 11 is located between the light reflector 47 and the scintillator 1. In a configuration in which the radiation detector RD1 includes a base 40, the light reflector 47 is disposed, for example, such that the semiconductor substrate 11 and the base 40 are located between the light reflector 47 and the scintillator 1. In this configuration, the scintillator 1, the semiconductor substrate 11, the base 40, and the light reflector 47 are arranged in this order. In a configuration in which the radiation detector RD1 does not include a base 40, for example, the scintillator 1, the semiconductor substrate 11, and the light reflector 47 are arranged in this order. The light reflector 47 may also be disposed on at least one of the end faces 1a, 1b and the side faces 1d, 1e, and 1f.

[0087] The light reflector 47 includes, for example, a metal. The metal included in the light reflector 47 includes, for example, Al, Ag, and Au. The light reflector 47 may include a multilayer optical film or Teflon (registered trademark). The light reflector 47 is formed by, for example, a plating method, a vapor deposition method, or a sputtering method. The thickness of the light reflector 47 is, for example, 0.05 to 100 μm. The radiation detector RD1 does not necessarily have to include the light reflector 47.

[0088] The path of scintillation light and a configuration for generating the path of scintillation light will be described with reference to FIGS. 5 to 8. FIG. 5 is a diagram showing the path of part of the scintillation light. FIG. 5 shows the path of part of the scintillation light when the scintillator 1 is viewed from the third direction D3. As described above, scintillation light is generated by radiation incident on the scintillator 1. For example, radiation enters the scintillator 1 from the end face 1a in the first direction D1. The semiconductor photodetector element 10 is disposed to face the side face 1c. In this embodiment, the refractive index of the scintillator 1 is, for example, 1.8, and the refractive index of the adhesive that bonds the semiconductor photodetector element 10 to the scintillator 1 is, for example, 1.5. Therefore, the critical angle of the scintillation light at the side face 1c is approximately 56.4 degrees. The illustrated radiation detector RD1 includes light reflectors 47 on the end faces 1a and 1b and the side faces 1d, 1e, and 1f. The scintillation light incident on the end faces 1a and 1b and the side faces 1d, 1e and 1f is totally reflected by the light reflector 47.

[0089] After being generated within the scintillator 1, the scintillation light propagates from the scintillation light generation point GP1 in all directions, for example, 360 degrees. Therefore, the scintillation light includes, for example, light L1 and L2 that are incident directly from the generation point GP1 onto the side surface 1c. The range of incident angles at which the light L1 and L2 can transmit through the side surface 1c is, for example, 0 to approximately 56.4 degrees. In the example shown in FIG. 5, the light L1 is incident on the side surface 1c at an incident angle of 0 degrees, which is the lower limit of the incident angle. The light L1 transmits through the side surface 1c and enters, for example, the photodetection region 23c. The light L2 is incident on the side surface 1c at an incident angle EA1, which is smaller than the upper limit of the incident angle, 56.4 degrees. If the light L2 is within a region RG1 shown on the side surface 1c, it is not totally reflected by the side surface 1c and transmits through the side surface 1c. Region RG1 indicates the maximum area through which light L2 passes through side surface 1c as viewed from third direction D3. Light L2 can also enter side surface 1c via the path indicated by the dashed line in FIG. 5. Light L2 that passes through side surface 1c enters one of photodetection regions 23a, 23b, 23c, and 23d and is detected by semiconductor photodetector element 10 arranged on side surface 1c. For example, if scintillation light is generated in the region of the scintillator corresponding to photodetection region 23a, among the multiple photodetection regions 23a, 23b, 23c, and 23d, for example, photodetection region 23a detects the most scintillation light. In this embodiment, for example, a signal processing circuit connected to wiring member 30 adds up electrical signals output in response to light incident on each of photodetection regions 23a, 23b, 23c, and 23d.

[0090] In addition to light L1 and L2, the scintillation light also includes light L3 that is initially incident on side surface 1d at an incident angle EA2. Light L3 is totally reflected by side surface 1d. After being totally reflected by side surface 1d, light L3 is incident on end surface 1b at an incident angle EA3, for example. After being totally reflected by end surface 1b, light L3 is incident on side surface 1c, for example. In the example shown in FIG. 5, the incident angle EA4 of light L3 on side surface 1c is smaller than the critical angle at side surface 1c. Light L3 is not totally reflected by side surface 1c and is transmitted through side surface 1c. Light L3 is incident on photodetection region 23d, for example.

[0091] Fig. 6 is a diagram showing the path of part of the scintillation light. Fig. 6 shows the path of part of the scintillation light when the scintillator 1 is viewed from a first direction D1. Fig. 6 shows that the path of the scintillation light from the generation point GP1 to the side surface 1c differs depending on the state of the side surfaces 1e and 1f of the scintillator 1. The semiconductor photodetector element 10 is disposed so as to face the side surface 1c.

[0092] In the scintillator 1 used as an example in FIG. 6, two surfaces, side surfaces 1e and 1f, are roughened. Two surfaces, side surfaces 1c and 1d, are mirror-finished. In addition to light L1, the scintillation light includes light L4 incident on side surface 1d from generation point GP1 at an incident angle EA5. Light L4 incident on side surface 1d is, for example, totally reflected by side surface 1d. After being totally reflected by side surface 1d, light L4 is incident on side surface 1e at an incident angle EA6. Since side surface 1e is roughened, light L4 incident on side surface 1e is diffusely reflected by side surface 1e and directed toward side surface 1c. The diffusely reflected light L4 can enter side surface 1c. If the incident angle EA7 of light L4 on side surface 1c is smaller than the critical angle at side surface 1c, light L4 incident on side surface 1c is detected by the semiconductor photodetector element 10 arranged on side surface 1c. Light L4 is incident on one of the photodetection regions 23a, 23b, 23c, and 23d. In the example shown in FIG. 6, light L4 is incident on the photodetection region 23a. Even if the incident angle EA7 is greater than the critical angle at side surface 1c, light L4 may be incident on side surface 1f, for example, after being reflected by side surface 1c. Side surface 1f has a roughened surface, and therefore may reflect light L4 toward side surface 1c. If the incident angle EA7 is greater than the critical angle at side surface 1c, light L4 may be reflected by side surface 1c and then re-enter side surface 1e via side surface 1d, for example. Light L4 that re-enters side surface 1e may be reflected by side surface 1e so that it re-enters side surface 1c at an incident angle smaller than the critical angle at side surface 1c. Because side surface 1e is roughened, light L4 that is incident on side surface 1e may exhibit different reflection angles with each reflection, even if the incident angles EA6 are approximately the same. Light L4 that is incident on side surface 1c at an incident angle smaller than the critical angle at side surface 1c is detected by semiconductor photodetector element 10. If side surface 1e is mirror-finished, light L4 reflected on side surface 1e is unlikely to exhibit different reflection angles with each reflection, even if the incident angles EA6 are approximately the same.

[0093] For comparison, FIG. 6 shows the path of light L5 incident on side surface 1e after being totally reflected by side surface 1d, assuming that side surfaces 1e and 1f are mirror-finished. Light L5 incident on side surface 1e at an incident angle EA6 is, for example, totally reflected by side surface 1e. Light L5 totally reflected by side surface 1e may be incident on side surface 1f at an incident angle EA6. Light L5 incident on side surface 1f is, for example, totally reflected by side surface 1f. Light L5 totally reflected by side surface 1f is incident on side surface 1c at an incident angle EA6a. If the incident angle EA6a is smaller than the critical angle at side surface 1c, light L5 is detected by the semiconductor photodetector element 10. Even in this case, the path from the generation point GP1 of light L5 to side surface 1c is longer than the path from the generation point GP1 of light L4 to side surface 1c. Light L4 is detected by the semiconductor photodetector element 10 with a shorter time lag than light L1 than light L5. The number of times that the light L4 is reflected by the side surface is smaller than the number of times that the light L5 is reflected by the side surface. In the example of FIG. 6, for example, when the incident angle EA6 is 30 degrees, the incident angle EA6a is 60 degrees. The incident angle EA6a is larger than the critical angle (approximately 56.4 degrees) at side surface 1c. Light L5 is totally reflected at side surface 1c and, for example, is incident again at side surface 1e. Light L5 is totally reflected at side surface 1e and, for example, is reflected again by side surfaces 1d, 1e, and 1f, respectively. Even when light L5 is incident on side surface 1c and detected by semiconductor photodetector element 10, it is subject to greater reflection attenuation than light L4, for example, due to reflection at side surfaces 1d, 1e, and 1f.

[0094] As shown in FIG. 6, the scintillation light also includes light L6 incident on side surface 1f from the generation point GP1. Side surface 1f has a rough surface finish. Light L6 incident on side surface 1f occurs at an incident angle EA8, for example. Light L6 may be directed toward side surface 1c due to diffuse reflection at side surface 1f. Light L6 may also be transmitted through side surface 1c. For comparison, FIG. 6 also shows, with a dashed line, the path of light L7 incident on side surface 1f, assuming that side surface 1f has a mirror finish. Light L7 incident on side surface 1f at an incident angle EA8 is totally reflected at side surface 1f and directed toward side surface 1e, for example. Thereafter, light L7 is repeatedly reflected at side surfaces 1f and 1e, for example, before entering side surface 1c and being detected by the semiconductor photodetector element 10. Light L7 experiences greater reflection attenuation than light L6.

[0095] Fig. 7 is a diagram showing the path of part of the scintillation light. Fig. 7 shows the path of part of the scintillation light when the scintillator 1 is viewed from the third direction D3. Fig. 7 shows that the path from the generation point GP1 to the side surface 1c differs depending on the state of the end surfaces 1a and 1b of the scintillator 1. The semiconductor photodetector element 10 is disposed so as to face the side surface 1c.

[0096] In the scintillator 1 used as an example in FIG. 7, two end faces 1a and 1b are roughened. Two side faces 1c and 1d are mirror-finished. As shown in FIG. 7, in addition to light L1, the scintillation light includes, for example, light L8 incident on side face 1d from generation point GP1. For example, light L8 incident on side face 1d at an incident angle EA9 is totally reflected by side face 1d. After being totally reflected by side face 1d, light L8 is incident on end face 1a at an incident angle EA10, for example. Since end face 1a is roughened, light L8 incident on end face 1a is diffusely reflected by end face 1a and directed toward side face 1c. The diffusely reflected light L8 may enter side face 1c. Light L8 passes through side face 1c and enters, for example, photodetection region 23a.

[0097] For comparison, FIG. 7 shows the path of light L9 incident on end face 1a after being totally reflected by side face 1d, assuming that end faces 1a and 1b are mirror-finished. For example, light L9 incident on end face 1a at an incident angle EA10 is totally reflected by end face 1a. Light L9 totally reflected by end face 1a may be incident on end face 1b at an incident angle EA11. Light L9 incident on end face 1b is totally reflected by end face 1b. Light L9 totally reflected by end face 1b is incident on side face 1c. Even if light L9 passes through side face 1c, the path from generation point GP1 of light L9 to side face 1c is longer than the path from generation point GP1 of light L8 to side face 1c. Light L8 is detected by semiconductor photodetector element 10 with a shorter time lag than light L1. The amount of light L8 detected by the semiconductor photodetector element 10 is greater than the amount of light L9 received.

[0098] As shown in FIG. 7, the scintillation light also includes light L10 incident on end face 1b from generation point GP1. End face 1b has a rough surface finish. For example, light L10 incident on end face 1b at an incident angle EA12 is diffusely reflected by end face 1b and directed toward side face 1c. Light L10 may be transmitted through side face 1c. For comparison, FIG. 7 also shows, with a dashed line, the path of light L11 incident on end face 1b, assuming that end face 1b has a mirror finish. Light L11 incident on end face 1b at incident angle EA12 is totally reflected by end face 1b and directed toward end face 1a. After that, light L11 is repeatedly reflected by end faces 1b and 1a, for example, before it enters side face 1c and is detected by semiconductor photodetector element 10.

[0099] As shown in Fig. 8, another side surface 1e adjacent to the side surface 1c may be roughened. Fig. 8 is a diagram showing an example of the contour shape of the other side surface. Fig. 8 shows an example of the contour shape of the other side surface 1e when the scintillator 1 is viewed from the first direction D1. In this embodiment, at least one of the side surfaces 1e, 1f and the end faces 1a, 1b that are roughened has a contour shape such as that shown in Fig. 8, for example.

[0100] When the side surface 1e is roughened, the cross section of the side surface 1e has, for example, a triangular wave shape. The triangular wave shape of the side surface 1e includes, for example, a plurality of edges 1j. When viewed from the first direction D1, the length W1 of each edge 1j is, for example, approximately 1.0 to 400 μm. The directions parallel to the edges 1j intersect with each other. The angle TH1 at which the edges 1j intersect with each other is, for example, approximately 20 to 160 degrees.

[0101] When the side surface 1e is roughened, the cross section of the side surface 1e has a triangular wave shape when viewed from the second direction D2. When viewed from the second direction D2, the length of each edge 1j is, for example, about 1.0 to 400 μm. When viewed from the second direction D2, the angle at which the edges 1j intersect with each other is, for example, about 20 to 160 degrees. When the end surfaces 1a, 1b and side surface 1f have a roughened surface, the end surfaces 1a, 1b and side surface 1f have a triangular wave shape as shown in FIG. 8.

[0102] At least one of the side surfaces 1e, 1f and end surfaces 1a, 1b that are roughened is, for example, a rough surface. In these roughened surfaces, the surface roughness of the surface is, for example, 0.5 to 200 μm. When the surface roughness of the roughened side surfaces 1e, 1f and end surfaces 1a, 1b is within the above range, the cross section of the side surfaces 1e, 1f and end surfaces 1a, 1b does not need to have a triangular wave shape. In this specification, the maximum height (Rz) is used to represent the surface roughness of the surface. The maximum height (Rz) is defined in JIS B 0601:2001 (ISO 4287:1997).

[0103] In this embodiment, at least one of the side surfaces 1e, 1f may be roughened, and at least one of the end surfaces 1a, 1b may be roughened. All of the side surfaces 1e, 1f and the end surfaces 1a, 1b may be roughened. All of the side surfaces 1e, 1f and the end surfaces 1a, 1b may be mirror-finished, and at least one of the end surfaces 1a, 1b may be roughened. All of the side surfaces 1e, 1f and the end surfaces 1a, 1b may be mirror-finished. All of the side surfaces 1e, 1f and the end surfaces 1a, 1b may be mirror-finished.

[0104] When at least one of the side surfaces 1c, 1d, 1e, and 1f and the end surfaces 1a and 1b is mirror-finished, the surface roughness of the mirror-finished surface is, for example, 0.001 to 0.1 μm. For example, the side surfaces 1c and 1d are mirror-finished.

[0105] A first modified example of the radiation detector RD1 according to the first embodiment will be described with reference to Figs. 9 and 10. Fig. 9 is a perspective view showing the radiation detector RD1 according to the first modified example of the first embodiment. Fig. 10 is a diagram showing the path of part of the scintillation light. Fig. 10 shows the path of part of the scintillation light when the scintillator 1 is viewed from a third direction D3. The radiation detector RD1 according to this modified example has the same configuration as the radiation detector RD1 according to the first embodiment, except for the configuration of the scintillator 1.

[0106] The scintillator 1 according to this modification has a pair of end faces 1a, 1b facing each other in the first direction D1, a pair of side faces 1c, 1d facing each other in the second direction D2, and a pair of side faces 1e, 1f facing each other in the third direction D3. The end faces 1a, 1b, the side faces 1c, 1d, and the side faces 1e, 1f form the outer surface of the scintillator 1. Unlike the first embodiment, in this modification, the end face 1a is inclined with respect to the second direction D2. The end face 1a is also inclined with respect to the first direction D1. The end face 1b extends in the second direction D2. When the side face 1f is viewed in the third direction D3, the angle AG1 that the end face 1a makes with respect to the second direction D2 is, for example, 10 to 80 degrees clockwise. The length of the side face 1d in the first direction D1 is shorter than the length of the side face 1c in the first direction D1. The end faces 1a, 1b and the side faces 1c, 1d have a rectangular shape when viewed, for example, from a direction perpendicular to these faces. The scintillator 1 has a rectangular shape when viewed from a first direction D1 and a second direction D2. The first direction D1 is the longitudinal direction of the scintillator 1.

[0107] In this modification, at least one of the side surfaces 1e, 1f and the end surfaces 1a, 1b may be roughened. At least one of the side surfaces 1e, 1f and the end surface 1b may be roughened. The end surface 1a does not have to be roughened. The side surfaces 1c, 1d are, for example, mirror-finished. When viewed from the second direction D2, one area formed by the outlines of the multiple light detection regions 23a, 23b, 23c, and 23d has a shape corresponding to the outline shape of the side surface 1c. In this modification, when viewed from the second direction D2, the outline shape of the side surface 1c is rectangular, and one area formed by the outlines of the multiple light detection regions 23a, 23b, 23c, and 23d has a rectangular outline shape corresponding to the outline shape of the side surface 1c. Each of the light detection regions 23a, 23b, 23c, and 23d has, for example, a rectangular outline shape corresponding to the outline shape of the side surface 1c.

[0108] As shown in FIG. 10 , the scintillation light includes, for example, light L1 that is directly incident on the side surface 1c from the generation point GP1. In addition to light L1, the scintillation light also includes light L12. Light L12, for example, first enters the side surface 1d and is totally reflected by the side surface 1d. In this modification, the end surface 1a is inclined with respect to the second direction D2. Therefore, the light L12 reflected by the side surface 1d is totally reflected by the end surface 1a. The end surface 1a is inclined with respect to the second direction D2 so that the light L12 is easily totally reflected toward the side surface 1c. The light L12 totally reflected by the end surface 1a is incident on the side surface 1c. The light L12 passes through the side surface 1c and, for example, enters the photodetection region 23a and is detected by the semiconductor photodetector element 10. A light reflector 47 is disposed on the end surfaces 1a, 1b, and side surface 1d.

[0109] The scintillation light also includes, for example, light L13. Light L13, for example, first enters side surface 1d, is totally reflected by side surface 1d, and then enters end surface 1b. Light L13 is illustrated for comparison with light L12. The magnitude of the incident angle EA15 of light L13 on side surface 1d is the same as the magnitude of the incident angle EA13 of light L12 on side surface 1d. After being totally reflected by side surface 1d, light L13 enters end surface 1b at, for example, an incident angle EA16. Although light L13 enters side surface 1d at the same incident angle as light L12, it is incident on end surface 1b extending in second direction D2 and therefore does not easily transmit through side surface 1c. Light L13 incident on end surface 1b is totally reflected by end surface 1b and enters side surface 1c at an incident angle EA16a. In the example shown in FIG. 10, the incident angle EA16a is greater than the critical angle at side surface 1c. 10, for example, if the angle of incidence EA15 is changed, the light L13 may be totally reflected by the end face 1b and then incident on the side face 1c. The scintillation light totally reflected by this end face 1b may enter, for example, the light detection region 23c and be detected by the semiconductor photodetector element 10.

[0110] A second modified example of the radiation detector RD1 according to the first embodiment will be described with reference to Fig. 11. Fig. 11 is a perspective view showing the radiation detector RD1 according to the second modified example of the first embodiment. The radiation detector RD1 according to this modified example has the same configuration as the radiation detector RD1 according to the first embodiment, except for the configuration of the scintillator 1.

[0111] The scintillator 1 according to this modification has a pair of end faces 1a, 1b facing each other in the first direction D1, a pair of side faces 1c, 1d facing each other in the second direction D2, and a pair of side faces 1e, 1f facing each other in the third direction D3. The end faces 1a, 1b, the side faces 1c, 1d, and the side faces 1e, 1f form the outer surface of the scintillator 1. Unlike the first embodiment, in this modification, the end faces 1a, 1b are inclined with respect to the second direction D2. The end faces 1a, 1b are also inclined with respect to the first direction D1. When the side face 1f is viewed in the third direction D3, the angle that the end face 1a forms with respect to the second direction D2 is, for example, 10 to 80 degrees clockwise. When the side face 1f is viewed in the third direction D3, the angle that the end face 1b forms with respect to the second direction D2 is, for example, 10 to 80 degrees counterclockwise. When viewed from the third direction D3, the side surfaces 1e and 1f have, for example, a trapezoidal shape. The length of the side surface 1d in the first direction D1 is smaller than the length of the side surface 1c in the first direction D1. The end surfaces 1a and 1b and the side surfaces 1c and 1d have a rectangular shape when viewed from a direction perpendicular to these surfaces. The scintillator 1 has, for example, a trapezoidal shape when viewed from the third direction D3, and a rectangular shape when viewed from the first direction D1 and the second direction D2. The first direction D1 is the longitudinal direction of the scintillator 1.

[0112] In this modification, at least one of the side surfaces 1e, 1f and the end surfaces 1a, 1b may be roughened. At least one of the side surfaces 1e, 1f may be roughened. The end surfaces 1a, 1b do not have to be roughened. The side surfaces 1c, 1d are, for example, mirror-finished. When viewed from the second direction D2, one area formed by the outlines of the multiple light detection regions 23a, 23b, 23c, and 23d has a shape corresponding to the outline shape of the side surface 1c. In this modification, when viewed from the second direction D2, the outline shape of the side surface 1c is rectangular, and one area formed by the outlines of the multiple light detection regions 23a, 23b, 23c, and 23d has a rectangular outline shape corresponding to the outline shape of the side surface 1c. Each of the light detection regions 23a, 23b, 23c, and 23d has, for example, a rectangular outline shape corresponding to the outline shape of the side surface 1c.

[0113] When viewed from the third direction D3, the end faces 1a and 1b are inclined with respect to the second direction D2 so that the scintillation light is easily totally reflected toward the side face 1c. The scintillation light incident on the end faces 1a and 1b is easily reflected by the end faces 1a and 1b and then incident on the side face 1c.

[0114] A third modified example of the radiation detector RD1 according to the first embodiment will be described with reference to Figs. 12 and 13. Fig. 12 is a perspective view showing the radiation detector RD1 according to the third modified example of the first embodiment. Fig. 13 is a diagram showing the path of part of the scintillation light. Fig. 13 shows the path of part of the scintillation light when the scintillator 1 is viewed from a third direction D3. The radiation detector RD1 according to this modified example has the same configuration as the radiation detector RD1 according to the first embodiment, except for the configuration of the scintillator 1.

[0115] The scintillator 1 according to this modification has a pair of end faces 1a, 1b facing each other in the first direction D1, a pair of side faces 1c, 1d facing each other in the second direction D2, and a pair of side faces 1e, 1f facing each other in the third direction D3. The end faces 1a, 1b, the side faces 1c, 1d, and the side faces 1e, 1f form the outer surface of the scintillator 1. Unlike the first embodiment, in this modification, the end faces 1a, 1b are inclined with respect to the second direction D2. The end faces 1a, 1b are also inclined with respect to the first direction D1. When the side face 1f is viewed in the third direction D3, the angle AG2 that the end face 1a makes with respect to the second direction D2 is, for example, 10 to 80 degrees clockwise. When the side face 1f is viewed in the third direction D3, the angle AG3 that the end face 1b makes with respect to the second direction D2 is, for example, 10 to 80 degrees clockwise. When viewed from the third direction D3, the side surfaces 1e and 1f have, for example, a parallelogram shape. The length of the side surface 1d in the first direction D1 is approximately equal to the length of the side surface 1c in the first direction D1. The end surfaces 1a and 1b and the side surfaces 1c and 1d have a rectangular shape when viewed from a direction perpendicular to these surfaces. The scintillator 1 has, for example, a parallelogram shape when viewed from the third direction D3, and a rectangular shape when viewed from the first direction D1 and the second direction D2. The first direction D1 is the longitudinal direction of the scintillator 1.

[0116] In this modification, at least one of the side surfaces 1e, 1f and the end surfaces 1a, 1b may be roughened. At least one of the side surfaces 1e, 1f may be roughened. The end surfaces 1a, 1b do not have to be roughened. The side surfaces 1c, 1d are, for example, mirror-finished. When viewed from the second direction D2, one area formed by the outlines of the multiple light detection regions 23a, 23b, 23c, and 23d has a shape corresponding to the outline shape of the side surface 1c. In this modification, when viewed from the second direction D2, the outline shape of the side surface 1c is rectangular, and one area formed by the outlines of the multiple light detection regions 23a, 23b, 23c, and 23d has a rectangular outline shape corresponding to the outline shape of the side surface 1c. Each of the light detection regions 23a, 23b, 23c, and 23d has, for example, a rectangular outline shape corresponding to the outline shape of the side surface 1c.

[0117] As shown in FIG. 13, the scintillation light includes, for example, light L1 that is directly incident on the side surface 1c from the generation point GP1. In addition to light L1, the scintillation light also includes light L14. Light L14, for example, first strikes the side surface 1d at an incident angle EA13, is totally reflected by the side surface 1d, and then strikes the end surface 1a at an incident angle EA14. The end surface 1a of this modification has, for example, the same inclination as the end surface 1a of the first modification of the first embodiment (see FIG. 10), and light L14 travels the same path as light L12 of the first modification of the first embodiment. Light L14 is likely to strike the side surface 1c. Light L14 passes through the side surface 1c and, for example, strikes the photodetection region 23a and is detected by the semiconductor photodetector element 10. Light reflectors 47 are arranged on the end surfaces 1a, 1b, and side surface 1d.

[0118] The scintillation light also includes light L15, and light L15 initially enters end face 1b at, for example, an incident angle EA17. In this modification, end face 1b is inclined with respect to second direction D2. Light L15 is totally reflected by end face 1b. Light L15 reflected by end face 1b may be incident on side face 1d at, for example, an incident angle EA18. Light L15 may be totally reflected by side face 1d and then incident on side face 1c. End face 1b is inclined with respect to second direction D2 so that light L15 is easily incident on side face 1c. Light L15 passes through side face 1c and, for example, enters photodetection region 23d and is detected by semiconductor photodetector element 10.

[0119] A fourth modified example of the radiation detector RD1 according to the first embodiment will be described with reference to Figs. 14 and 15. Fig. 14 is a perspective view showing the radiation detector RD1 according to the fourth modified example of the first embodiment. Fig. 15 is a diagram showing the path of part of the scintillation light. Fig. 15 shows the path of part of the scintillation light when the scintillator 1 is viewed from a first direction D1. The radiation detector RD1 according to this modified example has the same configuration as the radiation detector RD1 according to the first embodiment, except for the configuration of the scintillator 1.

[0120] The scintillator 1 according to this modification has a pair of end faces 1a, 1b facing each other in the first direction D1, and side faces 1c, 1g, 1h extending in the first direction D1 to connect the end faces 1a, 1b. The end faces 1a, 1b and the side faces 1c, 1g, 1h form the outer surface of the scintillator 1. The end faces 1a, 1b define both end faces of the scintillator 1 in the first direction D1. The side faces 1c, 1g, 1h extend in the first direction D1 to connect the end faces 1a, 1b. In this modification, the end faces 1a, 1b extend in the second direction D2. The side faces 1c, 1g are adjacent to each other, and the side faces 1c, 1h are adjacent to each other. The side faces 1g, 1h are adjacent to each other. The first direction D1 is the longitudinal direction of the scintillator 1. In this modification, the direction perpendicular to the side surface 1c corresponds to the second direction D2, and the direction parallel to the side surface 1c corresponds to the third direction D3.

[0121] When viewed from the first direction D1, the side surface 1g extends, for example, in the second direction D2. The side surface 1h is inclined, for example, with respect to the third direction D3. When the end surface 1a is viewed from the first direction D1, the angle AG4 that the side surface 1h forms with respect to the second direction D2 is, for example, 10 to 80 degrees counterclockwise. When viewed from the first direction D1, the end surfaces 1a and 1b have, for example, a triangular shape. When viewed from a direction perpendicular to these surfaces, the side surfaces 1c, 1g, and 1h have, for example, a rectangular shape. When viewed from the first direction D1, the scintillator 1 has, for example, a triangular shape, and when viewed from the second direction D2 and the third direction D3, has, for example, a rectangular shape.

[0122] In this modification, at least one of the side surfaces 1g, 1h and the end surfaces 1a, 1b may be roughened. At least one of the side surfaces 1g, 1a, 1b may be roughened. The side surface 1h does not have to be roughened. At least one of the end surfaces 1a, 1b may be roughened. All of the side surfaces 1g, 1a, 1b may be roughened. The side surface 1c is, for example, mirror-finished. The side surface 1h is inclined with respect to the second direction D2 so as to facilitate total reflection of scintillation light toward the side surface 1c. Light of scintillation light incident on the side surface 1h is likely to be reflected by the side surface 1h and then incident on the side surface 1c. When viewed from the second direction D2, one region formed by the outlines of the multiple photodetection regions 23a, 23b, 23c, and 23d has a shape corresponding to the outline shape of the side surface 1c. In this modification, when viewed from the second direction D2, the outline shape of the side surface 1c is rectangular, and one region formed by the outlines of the multiple photodetection regions 23a, 23b, 23c, and 23d has a rectangular outline shape corresponding to the outline shape of the side surface 1c. Each of the photodetection regions 23a, 23b, 23c, and 23d has, for example, a rectangular outline shape corresponding to the outline shape of the side surface 1c.

[0123] The length of the scintillator 1 in the first direction D1 is greater than the length of the scintillator 1 in the second direction D2. The length of the side surface 1c in the first direction D1 is greater than the width of the side surface 1c in the third direction D3. The length of the scintillator 1 in the first direction D1 is, for example, about 20 mm. The length of the scintillator 1 in the second direction D2 is, for example, about 4 mm. The length of the scintillator 1 in the third direction D3 is, for example, about 4 mm.

[0124] As shown in FIG. 15, the scintillation light includes, for example, light L1 that is directly incident on side surface 1c from generation point GP1. In addition to light L1, the scintillation light also includes light L16. Light L16, for example, first strikes side surface 1g at an incident angle EA19, is totally reflected by side surface 1g, and then strikes side surface 1c. Light L16 passes through side surface 1c, strikes one of photodetection regions 23a, 23b, 23c, or 23d, and is detected by semiconductor photodetector element 10. For example, if scintillation light is generated in a region of the scintillator corresponding to photodetection region 23a, of the multiple photodetection regions 23a, 23b, 23c, and 23d, for example, photodetection region 23a will detect the most scintillation light. Light reflectors 47 are disposed on side surfaces 1g and 1h.

[0125] The scintillation light also includes light L17. For example, light L17 first enters side surface 1h at an incident angle EA20, is reflected by side surface 1h, and then enters side surface 1c. Side surface 1h is inclined with respect to second direction D2. Light L17 can be totally reflected by side surface 1h and enters side surface 1c. Side surface 1h is inclined with respect to second direction D2 so as to facilitate total reflection of light L17 toward side surface 1c. Light L17 passes through side surface 1c and enters one of photodetection regions 23a, 23b, 23c, and 23d.

[0126] A fifth modified example of the radiation detector RD1 according to the first embodiment will be described with reference to Fig. 16 and Fig. 17. Fig. 16 is a perspective view showing the radiation detector RD1 according to the fifth modified example of the first embodiment. Fig. 17 is a plan view showing the semiconductor photodetector element. The radiation detector RD1 according to this modified example has the same configuration as the radiation detector RD1 according to the first embodiment, except for the configurations of the scintillator 1 and the photodetection region 23a.

[0127] As shown in FIG. 16 , the scintillator 1 according to this modification has a pair of end faces 1a, 1b facing each other in the first direction D1, and side faces 1c, 1g, and 1h extending in the first direction D1 to connect the end faces 1a, 1b. The end faces 1a, 1b and the side faces 1c, 1g, and 1h constitute the outer surface of the scintillator 1. The end faces 1a, 1b define both end faces of the scintillator 1 in the first direction D1. The side faces 1c, 1g, and 1h extend in the first direction D1 to connect the end faces 1a, 1b. In this modification, unlike the fourth modification of the first embodiment, the end face 1a is inclined with respect to the second direction D2. The end face 1a is also inclined with respect to the first direction D1. The end face 1b extends in the second direction D2. The side faces 1c, 1g are adjacent to each other, and the side faces 1c, 1h are adjacent to each other. The side surfaces 1g and 1h are adjacent to each other. The first direction D1 is the longitudinal direction of the scintillator 1. In this modification, the direction perpendicular to the side surface 1c coincides with the second direction D2, and the direction parallel to the side surface 1c coincides with the third direction D3.

[0128] When viewed from the first direction D1, the side surface 1g extends, for example, in the second direction D2. When the end surface 1a is viewed from the first direction D1, the side surface 1h forms an angle of 10 to 80 degrees, for example, counterclockwise, with respect to the second direction D2. When viewed from the first direction D1, the end surfaces 1a and 1b have, for example, a triangular shape. When viewed from a direction perpendicular to these surfaces, the side surfaces 1c and 1h have a rectangular shape. When viewed from the first direction D1, the scintillator 1 has, for example, a triangular shape.

[0129] When viewed from the second direction D2, of the pair of edges 2a, 2b of the side surface 1c in the first direction D1, the edge 2a on the side of the end face 1a forms an angle of 10 to 80 degrees counterclockwise with respect to the third direction D3, for example. When viewed from the second direction D2, the edge 2b on the side of the end face 1b extends in the third direction D3.

[0130] When viewed from the third direction D3, of a pair of edges 2c, 2d of the side surface 1g in the first direction D1, the edge 2d on the side of the end surface 1b extends in the second direction D2. When the side surface 1g is viewed from the third direction D3, the edge 2c on the side of the end surface 1a forms an angle of 10 to 80 degrees, for example, counterclockwise, with the second direction D2.

[0131] The length of the scintillator 1 in the first direction D1 is greater than the length of the scintillator 1 in the second direction D2. The length of the side surface 1c in the first direction D1 is greater than the width of the side surface 1c in the third direction D3. At least one of the side surfaces 1g, 1h and the end surfaces 1a, 1b may be roughened. At least one of the side surface 1g and the end surface 1b may be roughened. The side surface 1h and the end surface 1b do not have to be roughened. The side surface 1c is, for example, mirror-finished.

[0132] As shown in Fig. 17, when viewed from the second direction D2, one region formed by the outlines of the multiple photodetection regions 23a, 23b, 23c, and 23d has a shape corresponding to the outline shape of the side surface 1c. In this modification, when viewed from the second direction D2, the outline shape of the side surface 1c is rectangular, and one region formed by the outlines of the multiple photodetection regions 23a, 23b, 23c, and 23d has a rectangular outline shape corresponding to the outline shape of the side surface 1c. The photodetection region 23a has, for example, a triangular outline shape corresponding to the outline shape of the side surface 1c. The photodetection regions 23b, 23c, and 23d have, for example, a rectangular outline shape.

[0133] The photodetection regions 23a, 23b, 23c, and 23d are arranged, for example, in the first direction D1. In this embodiment, the photodetection regions 23a, 23b, 23c, and 23d are arranged in this order. The photodetection region 23d is closer to the second portion than the photodetection regions 23a, 23b, and 23c. The photodetection region 23c is closer to the second portion than the photodetection regions 23a and 23b. The photodetection region 23b is closer to the second portion than the photodetection region 23a. In this modification, the width of the conductive wire 14a is larger than the widths of the conductive wires 14b, 14c, and 14d. The width of the conductive wire 14b is larger than the widths of the conductive wires 14c and 14d. The width of the conductive wire 14c is larger than the width of the conductive wire 14d. When viewed from the second direction D2, for example, the conductive wire 14a and the conductive wires 14b and 14c extend between both ends of the semiconductor substrate 11 in the third direction D3 and the photodetection regions 23a, 23b, 23c, and 23d. When viewed from the second direction D2, the conductive wire 14d is disposed, for example, between the conductive wire 14a and the conductive wires 14b and 14c. The conductive wires 14a, 14b, 14c, and 14d extend in the first direction D1.

[0134] In this modification, end face 1a is inclined with respect to second direction D2 and first direction D1 so as to facilitate total reflection of scintillation light toward side face 1c. Of the scintillation light, light that is incident on end face 1a is likely to be reflected by end face 1a and then incident on side face 1c. Side face 1h is inclined with respect to second direction D2 so as to facilitate total reflection of scintillation light toward side face 1c. Of the scintillation light, light that is incident on side face 1h is likely to be reflected by side face 1h and then incident on side face 1c.

[0135] A sixth modified example of the radiation detector RD1 according to the first embodiment will be described with reference to Fig. 18 and Fig. 19. Fig. 18 is a perspective view showing the radiation detector RD1 according to the sixth modified example of the first embodiment. Fig. 19 is a plan view showing a semiconductor photodetector element. The radiation detector RD1 according to this modified example has the same configuration as the radiation detector RD1 according to the first embodiment, except for the configurations of the scintillator 1 and the photodetection regions 23a, 23b, and 23c.

[0136] The scintillator 1 according to this modification has a pair of end faces 1a, 1b facing each other in the first direction D1, and side faces 1c, 1g, 1h extending in the first direction D1 to connect the end faces 1a, 1b. The end faces 1a, 1b and the side faces 1c, 1g, 1h form the outer surface of the scintillator 1. The end faces 1a, 1b define both end faces of the scintillator 1 in the first direction D1. The side faces 1c, 1g, 1h extend in the first direction D1 to connect the end faces 1a, 1b. In this modification, the end faces 1a, 1b are inclined with respect to the second direction D2. The side faces 1c, 1g are adjacent to each other, and the side faces 1c, 1h are adjacent to each other. The side faces 1g, 1h are adjacent to each other. The first direction D1 is the longitudinal direction of the scintillator 1. In this modification, the direction perpendicular to the side surface 1c corresponds to the second direction D2, and the direction parallel to the side surface 1c corresponds to the third direction D3.

[0137] When viewed from the first direction D1, the side surface 1g extends, for example, in the second direction D2. When the end surface 1a is viewed from the first direction D1, the side surface 1h forms an angle of 10 to 80 degrees, for example, counterclockwise, with respect to the second direction D2. When viewed from a direction perpendicular to these surfaces, the end surfaces 1a and 1b have, for example, a triangular shape, and the side surface 1h has, for example, a rectangular shape when viewed from a direction perpendicular to this surface. When viewed from the first direction D1, the scintillator 1 has, for example, a triangular shape.

[0138] When viewed from the second direction D2, of a pair of edges 2a, 2b of the side surface 1c in the first direction D1, the edge 2a on the end face 1a side forms an angle of 10 to 80 degrees counterclockwise with respect to the third direction D3, for example. When viewed from the second direction D2, the edge 2b on the end face 1b side forms an angle of 10 to 80 degrees clockwise with respect to the third direction D3, for example.

[0139] When the side surface 1g is viewed in the third direction D3, of the pair of edges 2c, 2d of the side surface 1g in the first direction D1, the edge 2c on the side of the end surface 1a forms an angle of 10 to 80 degrees, for example, counterclockwise, with respect to the second direction D2. When the side surface 1g is viewed in the third direction D3, the edge 2d on the side of the end surface 1b forms an angle of 10 to 80 degrees, for example, clockwise, with respect to the second direction D2. When viewed in the third direction D3, the side surface 1g has, for example, a trapezoidal shape, and the distance between the edge 2c and the edge 2d decreases as the side surface 1g is farther away from the side surface 1c. When viewed in the third direction D3, the side surface 1h has, for example, a rectangular shape.

[0140] The length of the scintillator 1 in the first direction D1 is greater than the length of the scintillator 1 in the second direction D2. In this modification, the length of the side surface 1c in the first direction D1 is greater than the width of the side surface 1c in the third direction D3. When viewed from the second direction D2, the side surface 1c has, for example, a trapezoidal shape, and the distance between the edge 2a and the edge 2b decreases as the side surface 1c is farther away from the side surface 1g.

[0141] In this modification, for example, three photodetection regions 23a, 23b, and 23c are arranged in the first portion 21. For example, three conductors 14a, 14b, 14c and conductor 14e are also arranged in the first portion 21. A plurality of first electrodes 17a, 17b, and 17c and a second electrode 18 are arranged in the second portion 22. The first electrodes 17a, 17b, and 17c electrically connect the plurality of quenching resistors 13 included in the corresponding photodetection regions 23a, 23b, and 23c in parallel via the conductors 14a, 14b, and 14c, respectively. The first electrode 17a is connected to the photodetection region 23a via the conductor 14a. The first electrode 17b is connected to the photodetection region 23b via the conductor 14b. The first electrode 17c is connected to the photodetection region 23c via the conductor 14c. The second electrode 18 is electrically connected in parallel to the other of the anodes and cathodes of the multiple avalanche photodiodes 12 via conductive wires 14e.

[0142] When viewed from the second direction D2, one region formed by the outlines of the multiple photodetection regions 23a, 23b, and 23c has a shape corresponding to the outline shape of the side surface 1c. In this modification, when viewed from the second direction D2, the outline shape of the side surface 1c is trapezoidal, and one region formed by the outlines of the multiple photodetection regions 23a, 23b, and 23c has a trapezoidal outline shape corresponding to the outline shape of the side surface 1c. When viewed from the second direction D2, each of the photodetection regions 23a, 23b, and 23c has an outline shape corresponding to the outline shape of the side surface 1c. The photodetection region 23a has, for example, a triangular outline shape corresponding to the outline shape of the side surface 1c. The photodetection regions 23b and 23c have, for example, a parallelogram outline shape.

[0143] The photodetection regions 23a, 23b, and 23c are arranged, for example, in the first direction D1. In this modification, the photodetection regions 23a, 23b, and 23c are arranged in this order. The photodetection region 23c is closer to the second portion than the photodetection regions 23a and 23b. The photodetection region 23b is closer to the second portion than the photodetection region 23a. In this modification, the width of the conductive wire 14a is larger than the width of the conductive wires 14b and 14c. The width of the conductive wire 14b is larger than the width of the conductive wire 14c. When viewed from the second direction D2, for example, the conductive wires 14a and 14b and 14c extend between both ends of the semiconductor substrate 11 in the third direction D3 and the photodetection regions 23a, 23b, and 23c. The conductive wires 14a, 14b, and 14c extend in the first direction D1.

[0144] In this modification, the end faces 1a and 1b are inclined with respect to the second direction D2 and the first direction D1 so as to facilitate total reflection of the scintillation light toward the side face 1c. Light of the scintillation light that is incident on the end faces 1a and 1b is likely to be reflected by the end faces 1a and 1b and then incident on the side face 1c. The side face 1h is inclined with respect to the second direction D2 so as to facilitate total reflection of the scintillation light toward the side face 1c. Light of the scintillation light that is incident on the side face 1h is likely to be reflected by the side face 1h and then incident on the side face 1c. In this modification, at least one of the side faces 1g and 1h and the end faces 1a and 1b may be roughened. Only the side face 1g may be roughened. The side face 1h and the end faces 1a and 1b do not have to be roughened. The side face 1c is, for example, mirror-finished.

[0145] A seventh modified example of the radiation detector RD1 according to the first embodiment will be described with reference to Fig. 20 and Fig. 21. Fig. 20 is a perspective view showing the radiation detector RD1 according to the seventh modified example of the first embodiment. Fig. 21 is a plan view showing a semiconductor photodetector element. The radiation detector RD1 according to this modified example has the same configuration as the radiation detector RD1 according to the first embodiment, except for the configurations of the scintillator 1 and the photodetection regions 23a, 23b, and 23c.

[0146] The scintillator 1 according to this modification has a pair of end faces 1a, 1b facing each other in a first direction D1, and side faces 1c, 1g, 1h extending in the first direction D1 to connect the end faces 1a, 1b. The end faces 1a, 1b and the side faces 1c, 1g, 1h constitute the outer surface of the scintillator 1. The end faces 1a, 1b define both end faces of the scintillator 1 in the first direction D1. The side faces 1c, 1g, 1h extend in the first direction D1 to connect the end faces 1a, 1b. The end faces 1a, 1b are inclined with respect to the second direction D2. The end faces 1a, 1b are also inclined with respect to the first direction D1. The side faces 1c, 1g are adjacent to each other, and the side faces 1c, 1h are adjacent to each other. The side faces 1g, 1h are adjacent to each other. The first direction D1 is the longitudinal direction of the scintillator 1. In this modification, the direction perpendicular to the side surface 1c corresponds to the second direction D2, and the direction parallel to the side surface 1c corresponds to the third direction D3.

[0147] When viewed from the first direction D1, the side surface 1h extends, for example, in the second direction D2. When the end surface 1a is viewed from the first direction D1, the side surface 1g forms an angle of 10 to 80 degrees, for example, clockwise, with respect to the second direction D2. When viewed from the first direction D1, the end surfaces 1a and 1b have a triangular shape. When viewed from the first direction D1, the scintillator 1 has a triangular shape, for example.

[0148] When viewed from the second direction D2, of a pair of edges 2a, 2b of the side surface 1c in the first direction D1, the edge 2a on the end face 1a side forms an angle of, for example, 10 to 80 degrees clockwise with the third direction D3. When viewed from the second direction D2, the edge 2b on the end face 1b side forms an angle of, for example, 10 to 80 degrees clockwise with the third direction D3.

[0149] The first portion 21 includes, for example, three photodetection regions 23a, 23b, and 23c. The first portion 21 also includes, for example, three conductors 14a, 14b, and 14c and a conductor 14e. The second portion 22 includes, for example, a plurality of first electrodes 17a, 17b, and 17c and a second electrode 18. The first electrodes 17a, 17b, and 17c are electrically connected in parallel to a plurality of quenching resistors 13 included in the corresponding photodetection regions 23a, 23b, and 23c via the conductors 14a, 14b, and 14c, respectively. The first electrode 17a is connected to the photodetection region 23a via the conductor 14a. The first electrode 17b is connected to the photodetection region 23b via the conductor 14b. The first electrode 17c is connected to the photodetection region 23c via the conductor 14c. The second electrode 18 is electrically connected in parallel to the other of the anodes and cathodes of the multiple avalanche photodiodes 12 via conductive wires 14e.

[0150] When viewed from the second direction D2, one region formed by the outlines of the multiple photodetection regions 23a, 23b, and 23c has a shape corresponding to the outline shape of the side surface 1c. In this modification, when viewed from the second direction D2, the outline shape of the side surface 1c is a parallelogram, and one region formed by the outlines of the multiple photodetection regions 23a, 23b, and 23c has a parallelogram outline shape corresponding to the outline shape of the side surface 1c. When viewed from the second direction D2, each of the photodetection regions 23a, 23b, and 23c has a outline shape corresponding to the outline shape of the side surface 1c. Each of the photodetection regions 23a, 23b, and 23c has, for example, a parallelogram outline shape.

[0151] The photodetection regions 23a, 23b, and 23c are arranged, for example, in the first direction D1. In this modification, the photodetection regions 23a, 23b, and 23c are arranged in this order. The photodetection region 23c is closer to the second portion than the photodetection regions 23a and 23b. The photodetection region 23b is closer to the second portion than the photodetection region 23a. In this modification, the width of the conductive wire 14a is larger than the width of the conductive wires 14b and 14c. The width of the conductive wire 14b is larger than the width of the conductive wire 14c. When viewed from the second direction D2, for example, the conductive wires 14a and 14b and 14c extend between both ends of the semiconductor substrate 11 in the third direction D3 and the photodetection regions 23a, 23b, and 23c. The conductive wires 14a, 14b, and 14c extend in the first direction D1.

[0152] When the side surface 1h is viewed in the third direction D3, of the pair of edges 2e, 2f of the side surface 1h in the first direction D1, the edge 2e on the end surface 1a side forms an angle of, for example, 10 to 80 degrees clockwise with respect to the second direction D2. When the side surface 1h is viewed in the third direction D3, the edge 2f on the end surface 1b side forms an angle of, for example, 10 to 80 degrees clockwise with respect to the second direction D2. When the side surface 1h is viewed in the third direction D3, the side surface 1h has, for example, a parallelogram shape. When the side surface 1g is viewed in the third direction D3, the side surface 1g has, for example, a rectangular shape.

[0153] The length of the scintillator 1 in the first direction D1 is greater than the length of the scintillator 1 in the second direction D2. In this modified example, the length of the side surface 1c in the first direction D1 is greater than the width of the side surface 1c in the third direction D3. In this modified example, the end faces 1a, 1b and the side surface 1g are inclined with respect to the second direction D2 so as to facilitate total reflection of the scintillation light toward the side surface 1c. At least one of the side surfaces 1g, 1h and the end faces 1a, 1b may be roughened. Only the side surface 1h may be roughened. The side surface 1g and the end faces 1a, 1b do not have to be roughened. The side surface 1c is, for example, mirror-finished.

[0154] An eighth modified example of the radiation detector RD1 according to the first embodiment will be described with reference to Fig. 22 and Fig. 23. Fig. 22 is a perspective view showing the radiation detector RD1 according to the eighth modified example of the first embodiment. Fig. 23 is a diagram showing the path of part of the scintillation light. Fig. 23 shows the path of part of the scintillation light when the scintillator 1 is viewed from a third direction D3. The radiation detector RD1 according to this modified example has the same configuration as the radiation detector RD1 according to the first embodiment, except for the configuration of the scintillator 1.

[0155] 22, the scintillator 1 according to this modification has a plurality of portions 1p, 1q, 1r, and 1s. The plurality of portions 1p, 1q, 1r, and 1s correspond to the plurality of photodetection regions 23a, 23b, 23c, and 23d, respectively. The portion 1p corresponds to the photodetection region 23a. The portion 1q corresponds to the photodetection region 23b. The portion 1r corresponds to the photodetection region 23c. The portion 1s corresponds to the photodetection region 23d. The plurality of portions 1p, 1q, 1r, and 1s are independent of each other.

[0156] The portions 1p, 1q, 1r, and 1s each have a pair of opposing surfaces 3a and 3b facing each other, a pair of connecting surfaces 3c and 3d facing each other, and a pair of connecting surfaces 3e and 3f facing each other. The opposing surfaces 3a and 3b, the connecting surfaces 3c and 3d, and the connecting surfaces 3e and 3f constitute the outer surfaces of the portions 1p, 1q, 1r, and 1s. The opposing surfaces 3a and 3b face each other in a first direction D1. The first direction D1 is the longitudinal direction of the scintillator 1. The connecting surfaces 3c and 3d face each other in a second direction D2. The second direction D2 coincides with the direction perpendicular to the connecting surface 3c. The connecting surfaces 3e and 3f face each other in a third direction D3. In this modification, the opposing surface 3a of the portion 1p coincides with the end surface 1a of the scintillator 1, and the opposing surface 3b of the portion 1s coincides with the end surface 1b of the scintillator 1. The connecting surfaces 3c of the portions 1p, 1q, 1r, and 1s form the side surface 1c of the scintillator 1. The connecting surfaces 3d of the portions 1p, 1q, 1r, and 1s form the side surface 1d of the scintillator 1. The connecting surfaces 3e of the portions 1p, 1q, 1r, and 1s form the side surface 1e of the scintillator 1. The connecting surfaces 3f of the portions 1p, 1q, 1r, and 1s form the side surface 1f of the scintillator 1.

[0157] The opposing surfaces 3a and 3b extend in the second direction D2 to connect the connecting surfaces 3c and 3d. The opposing surfaces 3a and 3b extend in the third direction D3 to connect the connecting surfaces 3e and 3f. The connecting surfaces 3c and 3d extend in the first direction D1 to connect the opposing surfaces 3a and 3b. The connecting surfaces 3c and 3d extend in the third direction D3 to connect the connecting surfaces 3e and 3f. The connecting surfaces 3e and 3f extend in the first direction D1 to connect the opposing surfaces 3a and 3b. The connecting surfaces 3e and 3f extend in the second direction D2 to connect the connecting surfaces 3c and 3d. The connecting surfaces 3e and 3f are adjacent to the connecting surface 3c.

[0158] In this modification, the opposing surfaces 3a and 3b, the connecting surfaces 3c and 3d, and the connecting surfaces 3e and 3f are rectangular when viewed from a direction perpendicular to these surfaces. The portions 1p, 1q, 1r, and 1s are rectangular when viewed from the second direction D2 and the third direction D3. The portions 1p, 1q, 1r, and 1s are also rectangular when viewed from the first direction D1.

[0159] In this modification, the portions 1p, 1q, 1r, and 1s are aligned in the first direction D1. The lengths of the portions 1p, 1q, 1r, and 1s in the first direction D1 are, for example, approximately 0.05 to 100 mm. The lengths of the portions 1p, 1q, 1r, and 1s in the second direction D2 are, for example, approximately 0.05 to 20 mm. The lengths of the portions 1p, 1q, 1r, and 1s in the third direction D3 are, for example, approximately 0.05 to 20 mm. The portions 1p, 1q, 1r, and 1s may have sizes different from each other. For example, among the multiple portions 1p, 1q, 1r, and 1s, some portions 1p, 1q, and 1r may have approximately the same size, and other portions 1s may have sizes different from the portions 1p, 1q, and 1r. Some portions 1p and 1q may have approximately the same size, and other portions 1r and 1s may have different sizes from portions 1p and 1q but have approximately the same size. Portions 1p, 1q, 1r, and 1s may have approximately the same size.

[0160] The total length of portions 1p, 1q, 1r, and 1s in the first direction D1 is greater than the length of each of portions 1p, 1q, 1r, and 1s in the second direction D2. The total length of portions 1p, 1q, 1r, and 1s in the first direction D1 is greater than the length of portions 1p, 1q, 1r, and 1s that have the longest length in the second direction D2, among portions 1p, 1q, 1r, and 1s.

[0161] The portions 1p, 1q, 1r, and 1s may contain, for example, the same material as the scintillator 1 according to the first embodiment. The portions 1p, 1q, 1r, and 1s may contain, for example, the same material as one another. The portions 1p, 1q, 1r, and 1s may contain different materials from among the materials contained in the scintillator 1 according to the first embodiment. Therefore, for example, the portions 1p and 1r may contain the same material from among the materials of the scintillator 1 according to the first embodiment, and the portions 1q and 1s may contain the same material from among the materials of the scintillator 1 according to the first embodiment. In this case, the material contained in the portions 1p and 1r is different from the material contained in the portions 1q and 1s.

[0162] The portions 1p, 1q, 1r, and 1s are bonded to one another, for example. The opposing surface 3b of the portion 1p is bonded to the opposing surface 3a of the portion 1q, for example. The opposing surface 3b of the portion 1q is bonded to the opposing surface 3a of the portion 1r, for example. The opposing surface 3b of the portion 1r is bonded to the opposing surface 3a of the portion 1s, for example. The portions 1p, 1q, 1r, and 1s are bonded to one another, for example, by an adhesive.

[0163] The radiation detector RD1 according to this modification includes, for example, a light reflecting member 24. The light reflecting member 24 is disposed, for example, between the multiple portions 1p, 1q, 1r, and 1s. The portions 1p, 1q, 1r, and 1s are bonded to one another via the light reflecting member 24. The light reflecting member 24 is disposed, for example, between at least one of the portions 1p and 1q, the portions 1q and 1r, and the portions 1r and 1s. The portions 1p, 1q, 1r, and 1s are bonded to one another via the light reflecting member 24, for example, by an adhesive.

[0164] In this modification, the portions 1p, 1q, 1r, and 1s may be separated from one another and arranged side by side in the first direction D1. When the portions 1p, 1q, 1r, and 1s are separated from one another, for example, the atmosphere may exist between the portions 1p, 1q, 1r, and 1s. When the portions 1p, 1q, 1r, and 1s are separated from one another, a light reflecting member 24 may be disposed on at least one of the opposing surfaces 3a and 3b of the portions 1p, 1q, 1r, and 1s. In each of the portions 1p, 1q, 1r, and 1s, a light reflecting member 24 may be disposed on both the opposing surfaces 3a and 3b. A light reflecting member 24 may be disposed on one of the opposing surfaces 3a and 3b of the portions 1p, 1q, 1r, and 1s. Of the portions 1p, 1q, 1r, and 1s, for example, some portions 1p and 1q may be joined to each other, and the joined portions 1p and 1q and the remaining portions 1r and 1s may be separated from each other.

[0165] The light reflecting member 24 includes, for example, a metal, a multilayer optical film, or Teflon (registered trademark). The metal included in the light reflecting member 24 includes, for example, Al, Ag, and Au. The light reflecting member 24 is formed by, for example, a plating method, a vapor deposition method, or a sputtering method. The light reflecting member 24 has a thickness of, for example, 0.05 to 100 μm. The light reflecting member 24 can transmit radiation incident on the scintillator 1. The radiation detector RD2 does not necessarily have to include the light reflecting member 24.

[0166] In this modification, when viewed from the second direction D2, each of the multiple photodetection regions 23a, 23b, 23c, and 23d has a contour shape that corresponds to the contour shape of the coupling surface 3c of the corresponding one of the multiple portions 1p, 1q, 1r, and 1s, which faces the semiconductor substrate 11. In this modification, when viewed from the second direction D2, the coupling surfaces 3c of the portions 1p, 1q, 1r, and 1s are rectangular, and the corresponding photodetection regions 23a, 23b, 23c, and 23d have rectangular contour shapes.

[0167] FIG. 23 shows the path of scintillation light generated within portion 1p and incident on the coupling surface 3c. The scintillation light generated within portion 1p is, for example, confined within portion 1p. In this modification, a light-reflecting member 24 is disposed on the opposing surface 3b, and light reflectors 47 are disposed on the opposing surface 3a and the coupling surface 3d. Radiation is incident on the opposing surface 3a of portion 1p. The scintillation light includes, for example, light L1 that is incident directly on the coupling surface 3c from the generation point GP1. In addition to light L1, the scintillation light also includes, for example, light L18 that is initially incident on the opposing surface 3a at an incident angle EA21. After being totally reflected by the opposing surface 3a, light L18 is incident on, for example, the coupling surface 3c. Light L18 passes through the coupling surface 3c and enters the photodetection region 23a. The scintillation light also includes, for example, light L19 that first enters the opposing surface 3b at an incident angle EA22. After being totally reflected by the opposing surface 3b, the light L19 enters, for example, the coupling surface 3c. The light L19 passes through the coupling surface 3c and enters the photodetection region 23a. In FIG. 23, if the incident angles EA21 and EA22 are the same, the light L18 and the light L19 may have the same incident angle when they enter the coupling surface 3c.

[0168] In this modification, the scintillation light generated in the portions 1q, 1r, and 1s also enters the photodetection regions 23b, 23c, and 23d, respectively, and is detected by the semiconductor photodetector element 10 arranged on the coupling surface 3c. The scintillation light generated in the portions 1q, 1r, and 1s is, for example, confined within the portions 1q, 1r, and 1s, respectively. In this modification, for example, a signal processing circuit connected to the wiring member 30 adds up the electrical signals output in response to the incidence of the scintillation light on the photodetection regions 23a, 23b, 23c, and 23d. In this modification, for example, a light reflector 47 is arranged on the opposing surfaces 3a and 3b, the coupling surfaces 3c and 3d, and the coupling surfaces 3e and 3f of the portions 1p, 1q, 1r, and 1s, where the light reflecting member 24 is not arranged.

[0169] When the light reflecting member 24 is disposed between the portions 1p, 1q, 1r, and 1s, scintillation light generated in the scintillator 1 corresponding to each of the photodetection regions 23a, 23b, 23c, and 23d is reliably detected by each of the photodetection regions 23a, 23b, 23c, and 23d. Therefore, the signal processing circuit connected to the wiring member 30 processes the electrical signals output in response to the incidence of scintillation light for each of the photodetection regions 23a, 23b, 23c, and 23d. Even if the portions 1p, 1q, 1r, and 1s are separated from one another and aligned in the first direction D1, the scintillation light generated in the portion 1p does not, for example, enter the portion 1q. In this case, the scintillation light generated in the portion 1p corresponding to the photodetection region 23a is individually detected by the photodetection region 23a. When the scintillation light generated in the portions 1q, 1r, and 1s is confined to the portions 1q, 1r, and 1s, respectively, the scintillation light generated in the portions 1q, 1r, and 1s is detected individually by the photodetection regions 23b, 23c, and 23d.

[0170] In this modification, the pair of opposing surfaces 3a, 3b extend in the second direction D2. The cross sections of the opposing surfaces 3a, 3b have, for example, a triangular wave shape as illustrated in FIG. 8. The opposing surfaces 3a, 3b may be roughened, for example. When the opposing surfaces 3a, 3b are roughened, the cross sections of the opposing surfaces 3a, 3b do not have to have a triangular wave shape. When the cross sections of the opposing surfaces 3a, 3b have a triangular wave shape, the opposing surfaces 3a, 3b do not have to have a roughened surface. The scintillator 1 of this modification may have another connecting surface 3e that connects the opposing surfaces 3a, 3b and is adjacent to the connecting surface 3c and has a triangular wave shape in cross section. The scintillator 1 of this modification may have another connecting surface 3e that connects the opposing surfaces 3a, 3b and is adjacent to the connecting surface 3c and is a rough surface.

[0171] In the portions 1p, 1q, 1r, and 1s, at least one of the connecting surfaces 3e, 3f may be roughened, and at least one of the opposing surfaces 3a, 3b may be roughened. The connecting surfaces 3e, 3f and the opposing surfaces 3a, 3b may all be roughened. The connecting surfaces 3e, 3f may be mirror-finished, and at least one of the opposing surfaces 3a, 3b may be roughened. At least one of the connecting surfaces 3e, 3f may be roughened, and the opposing surfaces 3a, 3b may be mirror-finished. The connecting surfaces 3e, 3f and the opposing surfaces 3a, 3b may all be mirror-finished. For example, when the portions 1p, 1q, 1r, and 1s are joined to each other, the opposing surfaces 3a, 3b do not need to be roughened.

[0172] In the above, in this modification, the scintillator 1 having the plurality of portions 1p, 1q, 1r, and 1s has the same rectangular parallelepiped shape as the scintillator 1 of the first embodiment. In this modification, at least one of the pair of opposing surfaces 3a, 3b may be inclined with respect to the second direction D2. The scintillator 1 having the plurality of portions 1p, 1q, 1r, and 1s may have the same shape as the scintillators 1 of the first to seventh modifications of the first embodiment. When the scintillator 1 of this modification has the same shape as the scintillator 1 of the first to seventh modifications of the first embodiment, the scintillation light generated in the portions 1p, 1q, 1r, and 1s can each take the following paths.

[0173] When the scintillator 1 having the multiple portions 1p, 1q, 1r, and 1s has the same configuration as the scintillator 1 of the first modified example of the first embodiment, for example, the facing surface 3a of the portion 1p is inclined with respect to the second direction D2. Scintillation light incident on the facing surface 3a of the portion 1p is likely to be incident on the connecting surface 3c of the portion 1p (see FIG. 10). The scintillation light incident on the connecting surface 3c of the portion 1p is detected in the light detection region 23a.

[0174] When the scintillator 1 having the multiple portions 1p, 1q, 1r, and 1s has the same configuration as the scintillator 1 of the second modified example of the first embodiment, the facing surface 3a of the portion 1p is inclined with respect to the second direction D2. Scintillation light incident on the facing surface 3a of the portion 1p is likely to be incident on the coupling surface 3c of the portion 1p. Scintillation light incident on the coupling surface 3c of the portion 1p is detected in the photodetection region 23a. The facing surface 3b of the portion 1s is inclined with respect to the second direction D2. Scintillation light incident on the facing surface 3b of the portion 1s is likely to be incident on the coupling surface 3c of the portion 1s. Scintillation light incident on the coupling surface 3c of the portion 1s is detected in the photodetection region 23d.

[0175] When the scintillator 1 having the multiple portions 1p, 1q, 1r, and 1s has the same configuration as the scintillator 1 of the third modified example of the first embodiment, the facing surface 3a of the portion 1p is inclined with respect to the second direction D2. Scintillation light incident on the facing surface 3a of the portion 1p is likely to be incident on the coupling surface 3c of the portion 1p (see FIG. 13). Scintillation light incident on the coupling surface 3c of the portion 1p is detected in the photodetection region 23a. The facing surface 3b of the portion 1s is inclined with respect to the second direction D2. Scintillation light incident on the facing surface 3b of the portion 1s is likely to be incident on the coupling surface 3c of the portion 1s (see FIG. 13). Scintillation light incident on the coupling surface 3c of the portion 1s is detected in the photodetection region 23d.

[0176] When a scintillator 1 having a plurality of portions 1p, 1q, 1r, and 1s has the same configuration as the scintillator 1 of the fourth modified example of the first embodiment, among the connecting surfaces of the portions 1p, 1q, 1r, and 1s, the connecting surface constituting a part of the side surface 1h is inclined with respect to the second direction D2. Scintillation light incident on each connecting surface constituting a part of the side surface 1h is likely to be incident on each connecting surface 3c of the portions 1p, 1q, 1r, and 1s (see FIG. 15). Scintillation light incident on each connecting surface 3c of the portions 1p, 1q, 1r, and 1s is detected in the light detection regions 23a, 23b, 23c, and 23d, respectively. When viewed from the first direction D1, the scintillator 1 of this modified example has, for example, a triangular shape.

[0177] When the scintillator 1 having the plurality of portions 1p, 1q, 1r, and 1s has the same configuration as the scintillator 1 of the fifth modified example of the first embodiment, among the coupling surfaces of the portions 1p, 1q, 1r, and 1s, the coupling surface constituting a part of the side surface 1h is inclined with respect to the second direction D2. Scintillation light incident on each coupling surface constituting a part of the side surface 1h is likely to be incident on each coupling surface 3c of the portions 1p, 1q, 1r, and 1s. Scintillation light incident on each coupling surface 3c of the portions 1p, 1q, 1r, and 1s is detected by the photodetection regions 23a, 23b, 23c, and 23d, respectively. The facing surface 3a of the portion 1p is inclined with respect to the second direction D2. Scintillation light incident on the facing surface 3a of the portion 1p is likely to be incident on the coupling surface 3c of the portion 1p. Scintillation light incident on the coupling surface 3c of the portion 1p is detected by the photodetection region 23a.

[0178] When the scintillator 1 of this modification has the same configuration as the scintillator 1 of the sixth modification of the first embodiment, it has three portions 1p, 1q, and 1r. The portion 1p corresponds to the photodetection region 23a. The portion 1q corresponds to the photodetection region 23b. The portion 1r corresponds to the photodetection region 23c. In this case, for example, among the coupling surfaces of the portions 1p, 1q, and 1r, the coupling surface constituting a part of the side surface 1h is inclined with respect to the second direction D2. Scintillation light incident on each coupling surface constituting a part of the side surface 1h is likely to be incident on each coupling surface 3c of the portions 1p, 1q, and 1r. Scintillation light incident on each coupling surface 3c of the portions 1p, 1q, and 1r is detected by the photodetection regions 23a, 23b, and 23c, respectively. The opposing surface 3a of the portion 1p is inclined with respect to the second direction D2. Scintillation light incident on the facing surface 3a of the portion 1p is likely to be incident on the connecting surface 3c of the portion 1p. Scintillation light incident on the connecting surface 3c of the portion 1p is detected by the photodetection region 23a. The facing surface 3b of the portion 1r is inclined with respect to the second direction D2. Scintillation light incident on the facing surface 3b of the portion 1r is likely to be incident on the connecting surface 3c of the portion 1r. Scintillation light incident on the connecting surface 3c of the portion 1r is detected by the photodetection region 23c.

[0179] When the scintillator 1 of this modification has the same configuration as the scintillator 1 of the seventh modification of the first embodiment, it has three portions 1p, 1q, and 1r. The portion 1p corresponds to the photodetection region 23a. The portion 1q corresponds to the photodetection region 23b. The portion 1r corresponds to the photodetection region 23c. In this case, for example, among the coupling surfaces of the portions 1p, 1q, and 1r, the coupling surface constituting a part of the side surface 1g is inclined with respect to the second direction D2. Scintillation light incident on each coupling surface constituting a part of the side surface 1g is likely to be incident on each coupling surface 3c of the portions 1p, 1q, and 1r. Scintillation light incident on each coupling surface 3c of the portions 1p, 1q, and 1r is detected by the photodetection regions 23a, 23b, and 23c, respectively. The opposing surface 3a of the portion 1p is inclined with respect to the second direction D2. Scintillation light incident on the facing surface 3a of the portion 1p is likely to be incident on the connecting surface 3c of the portion 1p. Scintillation light incident on the connecting surface 3c of the portion 1p is detected by the photodetection region 23a. The facing surface 3b of the portion 1r is inclined with respect to the second direction D2. Scintillation light incident on the facing surface 3b of the portion 1r is likely to be incident on the connecting surface 3c of the portion 1r. Scintillation light incident on the connecting surface 3c of the portion 1r is detected by the photodetection region 23c.

[0180] As described above, the radiation detector RD1 includes a scintillator 1 having a pair of end faces 1a, 1b facing each other in a first direction D1 and a side face 1c connecting the pair of end faces 1a, 1b; a semiconductor photodetector element 10 having a semiconductor substrate 11 arranged to face the side face 1c; and a wiring member 30 electrically connected to the semiconductor photodetector element 10. The length of the scintillator 1 in the first direction D1 is greater than the length of the scintillator 1 in a second direction D2 perpendicular to the side face 1c. The length of the side face 1c in the first direction D1 is greater than the width of the side face 1c in a third direction D3 perpendicular to the first direction D1 and the second direction D2. The semiconductor substrate 11 is covered by the side face 1c and includes a first portion 21 in which multiple photodetection regions 23a, 23b, 23c, and 23d are arranged, and a second portion 22 aligned with the first portion 21 in the first direction D1 and exposed from the side face 1c. The multiple photodetection regions 23a, 23b, 23c, and 23d are aligned in the first direction D1, and each includes at least one avalanche photodiode 12 operating in Geiger mode and at least one quenching resistor 13 electrically connected in series with one of the anode and the cathode of a corresponding one of the at least one avalanche photodiode 12. The second portion 22 includes multiple first electrodes 17a, 17b, 17c, and 17d electrically connected to at least one quenching resistor 13 included in a corresponding one of the multiple photodetection regions 23a, 23b, 23c, and 23d, and a second electrode 18 electrically connected to the other of the anode and the cathode of each avalanche photodiode 12. The wiring member 30 has a plurality of conductors 31a, 31b, 31c, 31d that are electrically connected to corresponding first electrodes 17a, 17b, 17c, 17d among the plurality of first electrodes 17a, 17b, 17c, 17d, and a conductor 32 that is connected to the second electrode 18.

[0181] The radiation detector RD1 includes a scintillator 1 that is long in the first direction D1, and a semiconductor photodetector element 10 that is arranged on a side surface 1c of the scintillator 1. The semiconductor photodetector element 10 not only detects scintillator 1 light that is directly incident on the side surface 1c on which the semiconductor photodetector element 10 is arranged, but also detects, for example, scintillation light that is reflected by another side surface 1d that faces the side surface 1c on which the semiconductor photodetector element 10 is arranged and then incident on the side surface 1c. Because the length of the scintillator 1 in the second direction D2 is shorter than the length of the scintillator 1 in the first direction D1, the scintillation light that is directly incident on the side surface 1c and the scintillation light that is reflected by the other side surface 1d and then incident on the side surface 1c are detected by the semiconductor photodetector element 10 with a small time difference. Therefore, the radiation detector RD1 achieves high time resolution. The length of the side surface 1c in the first direction D1 is greater than the length of the end surface 1b in the second direction D2, for example. Therefore, compared to a configuration in which the semiconductor photodetector element 10 is disposed on the end surface 1b, for example, it is possible to receive scintillation light that is incident on the side surface 1c at a larger incident angle EA1.

[0182] The radiation detector RD1 includes a semiconductor photodetector element in which a plurality of photodetection regions 23a, 23b, 23c, and 23d are arranged in a first direction D1. For example, the distance in the first direction D1 between the scintillation light generation point GP1 and one end surface 1a of the scintillator 1 can be determined from the position of the photodetection region 23a, 23b, 23c, and 23d that detects the most scintillation light. As a result, the magnitude of the energy of the radiation incident on the scintillator 1 can be accurately measured. Therefore, the radiation detector RD1 achieves high energy resolution.

[0183] In the radiation detector RD1, at least one of the pair of end faces 1a, 1b is inclined with respect to the second direction D2. In this case, the scintillation light is more reliably incident on the side surface 1c. The number of times the scintillation light is reflected by the end surfaces 1a, 1b or the side surfaces 1d, 1e, 1f, 1g, and 1h is reduced, and the return attenuation is also reduced. Therefore, the radiation detector RD1 more reliably improves the amount of light received by the semiconductor photodetector element 10.

[0184] In the radiation detector RD1, of the pair of end faces 1a, 1b, the end faces 1a, 1b extending in the second direction D2 have a triangular wave shape in cross section. In this case, the scintillation light is more reliably incident on the side surface 1c. The number of times the scintillation light is reflected by the end surfaces 1a, 1b or the side surfaces 1d, 1e, 1f, 1g, and 1h is reduced, and the return attenuation is also reduced. This further reliably improves the amount of light received by the semiconductor photodetector element 10 of the radiation detector RD1. When the cross sections of the end faces 1a, 1b have a triangular wave shape, the amount of light received by the semiconductor photodetector element 10 is more reliably improved without tilting the end faces 1a, 1b with respect to the second direction D2. In a configuration in which the end faces 1a, 1b extend in the second direction D2, the radiation detector RD1 can be manufactured using less scintillator than in a configuration in which the end faces 1a, 1b are tilted with respect to the second direction D2.

[0185] In the radiation detector RD1, of the pair of end faces 1a, 1b, the end faces 1a, 1b extending in the second direction D2 are rough surfaces. In this case, the scintillation light is more reliably incident on the side surface 1c. The number of times the scintillation light is reflected by the end surfaces 1a, 1b or the side surfaces 1d, 1e, 1f, 1g, and 1h is reduced, and the return attenuation is also reduced. This further reliably improves the amount of light received by the semiconductor photodetector element 10 of the radiation detector RD1.

[0186] In the radiation detector RD1, the scintillator 1 has other side surfaces 1e, 1f, 1g, and 1h that connect the pair of end surfaces 1a and 1b and are adjacent to the side surface 1c, and have a triangular wave shape in cross section. In this case, scintillation light is more reliably incident on the side surface 1c on which the scintillator 1 is disposed. Therefore, the radiation detector RD1 more reliably improves the amount of light received by the semiconductor photodetector element 10.

[0187] In the radiation detector RD1, the scintillator 1 has rough side surfaces 1e, 1f, 1g, and 1h that connect the pair of end surfaces 1a and 1b and are adjacent to the side surface 1c. In this case, scintillation light is more reliably incident on the side surface 1c on which the scintillator 1 is disposed. Therefore, the radiation detector RD1 more reliably improves the amount of light received by the semiconductor photodetector element 10.

[0188] In the radiation detector RD1, when viewed from the second direction D2, one region formed by the outlines of the plurality of light detection regions 23a, 23b, 23c, and 23d has a shape corresponding to the outline shape of the side surface 1c. In this case, the photodetection regions 23a, 23b, 23c, and 23d do not need to be disposed in locations on the semiconductor substrate 11 that cannot receive scintillation light, thereby suppressing increases in dark count and capacitance in the photodetection regions 23a, 23b, 23c, and 23d. Therefore, this configuration reliably improves the time resolution and energy resolution of the radiation detector RD1.

[0189] In radiation detector RD1, scintillator 1 has a plurality of independent portions 1p, 1q, 1r, and 1s corresponding to the plurality of photodetection regions 23a, 23b, 23c, and 23d, respectively. Each of the plurality of portions 1p, 1q, 1r, and 1s has a pair of opposing surfaces 3a and 3b facing each other in first direction D1, and a connecting surface 3c connecting the pair of opposing surfaces 3a and 3b and facing semiconductor substrate 11. In this case, the scintillation light generated in each of the portions 1p, 1q, 1r, and 1s is confined within the portions 1p, 1q, 1r, and 1s. The photodetection regions 23a, 23b, 23c, and 23d corresponding to the portions 1p, 1q, 1r, and 1s reliably detect the scintillation light generated within the portions 1p, 1q, 1r, and 1s. Therefore, the radiation detector RD1 reliably achieves high energy resolution.

[0190] In the radiation detector RD1, the multiple portions 1p, 1q, 1r, and 1s are joined to one another. In this case, the physical strength of the scintillator 1 is improved, and therefore the radiation detector RD1 more reliably achieves high energy resolution.

[0191] The radiation detector RD1 may further include a light reflecting member 24. The light reflecting member 24 is disposed between the plurality of portions 1p, 1q, 1r, and 1s. In this case, the scintillation light generated in each of the portions 1p, 1q, 1r, and 1s is reliably confined within the portions 1p, 1q, 1r, and 1s. The photodetection regions 23a, 23b, 23c, and 23d corresponding to the portions 1p, 1q, 1r, and 1s more reliably detect the scintillation light generated within the portions 1p, 1q, 1r, and 1s. Therefore, the radiation detector RD1 more reliably achieves high energy resolution.

[0192] In the radiation detector RD1, at least one of the pair of opposing surfaces 3a, 3b is inclined with respect to the second direction D2. In this case, the scintillation light is more reliably incident on the coupling surface 3c. Since the number of times the scintillation light is reflected by the opposing surfaces 3a and 3b or the coupling surface is reduced and the return loss is also reduced, this configuration more reliably improves the amount of light received by the semiconductor photodetector element 10.

[0193] In the radiation detector RD1, of the pair of opposing surfaces 3a, 3b, the opposing surfaces 3a, 3b extending in the second direction D2 have a triangular wave shape in cross section. In this case, the scintillation light is more reliably incident on the coupling surface 3c. Since the number of times the scintillation light is reflected by the opposing surfaces 3a and 3b or the coupling surface is reduced and the return loss is also reduced, this configuration more reliably improves the amount of light received by the semiconductor photodetector element 10.

[0194] In the radiation detector RD1, of the pair of opposing surfaces 3a, 3b, the opposing surfaces 3a, 3b extending in the second direction D2 are rough surfaces. In this case, the scintillation light is more reliably incident on the coupling surface 3c. Since the number of times the scintillation light is reflected by the opposing surfaces 3a and 3b or the coupling surface is reduced and the return loss is also reduced, this configuration more reliably improves the amount of light received by the semiconductor photodetector element 10.

[0195] In the radiation detector RD1, the scintillator 1 has other coupling surfaces 3e and 3f, which connect the pair of opposing surfaces 3a and 3b and are adjacent to the coupling surface 3c, and which have a triangular wave shape in cross section. In this case, the scintillation light is more reliably incident on the coupling surface 3c. Therefore, this configuration more reliably improves the amount of light received by the semiconductor photodetector element 10.

[0196] In the radiation detector RD1, the scintillator 1 has other rough coupling surfaces 3e and 3f that couple the pair of opposing surfaces 3a and 3b and are adjacent to the coupling surface 3c. In this case, the scintillation light is more reliably incident on the coupling surface 3c. Therefore, this configuration more reliably improves the amount of light received by the semiconductor photodetector element 10.

[0197] In the radiation detector RD1, when viewed from the second direction D2, each of the multiple light detection regions 23a, 23b, 23c, and 23d has a contour shape that corresponds to the contour shape of the connecting surface 3c facing the semiconductor substrate 11 of the corresponding portion 1p, 1q, 1r, and 1s among the multiple portions 1p, 1q, 1r, and 1s. In this case, the photodetection regions 23 a, 23 b, 23 c, and 23 d do not need to be disposed in locations on the semiconductor substrate 11 that cannot receive scintillation light, thereby suppressing increases in dark count and capacitance in each of the photodetection regions 23 a, 23 b, 23 c, and 23 d. Therefore, this configuration reliably improves the time resolution and energy resolution of the radiation detector RD1.

[0198] In the radiation detector RD1, the scintillator 1 has a rectangular or triangular shape when viewed from a first direction D1. In this case, scintillation light is reliably incident on the side surface 1c on which the scintillator 1 is disposed. Therefore, this configuration reliably improves the amount of light received by the semiconductor photodetector element 10.

[0199] In the radiation detector RD1, the multiple photodetection regions 23a, 23b, 23c, and 23d include a first photodetection region 23a and a second photodetection region 23d that is closer to the second portion 22 than the first photodetection region 23a. The width of the conducting wire 14a that electrically connects the first electrode 17a corresponding to the first photodetection region 23a to the first photodetection region 23a is greater than the width of the conducting wire 14d that electrically connects the first electrode 17d corresponding to the second photodetection region 23d to the second photodetection region 23d. In this case, the difference in electrical resistance between the conductor 14a electrically connecting the first electrode 17a corresponding to the first photodetection region 23a to the first photodetection region 23a and the conductor 14d electrically connecting the first electrode 17d corresponding to the second photodetection region 23d to the second photodetection region 23d is reduced. The length of the conductor 14a electrically connecting the first electrode 17a corresponding to the first photodetection region 23a to the first photodetection region 23a is longer than the length of the conductor 14d electrically connecting the first electrode 17d corresponding to the second photodetection region 23d to the second photodetection region 23d. The longer the conductors 14a and 14d, the higher the electrical resistance of the conductors 14a and 14d. Therefore, in a configuration in which the width of the long conductor 14a is larger than the width of the short conductor 14d, the difference in electrical resistance between the long conductor 14a and the short conductor 14d is reduced. Therefore, this configuration more reliably improves the time resolution of the radiation detector RD1.

[0200] Radiation detector RD1 further includes a base 40 arranged such that the semiconductor substrate 11 is located between the base 40 and the scintillator 1. The base 40 has a third portion covered with the semiconductor substrate 11 and a fourth portion aligned with the third portion in the first direction D1 and exposed from the semiconductor substrate 11. The fourth portion includes a first terminal 41 and a second terminal 42 arranged on the same side of the semiconductor substrate 11 as the scintillator 1. The first terminal 41 is electrically connected to the first electrodes 17a, 17b, 17c, and 17d by a first wire 43, and the second terminal 42 is electrically connected to the second electrode 18 by a second wire 44. In this case, the mechanical strength of the radiation detector RD1 is reinforced. Therefore, this configuration reliably realizes a radiation detector RD1 with reinforced mechanical strength.

[0201] In the radiation detector RD1, the first wire 43 and the second wire 44 are covered with a resin 45. In this case, the first and second wires 43, 44 are protected from damage. Therefore, this configuration suppresses deterioration of the electrical connection between the first and second terminals 41, 42 and the first and second electrodes 17, 18.

[0202] The radiation detector RD1 further includes a light reflector 47 that is arranged so that the semiconductor substrate 11 is located between the light reflector 47 and the scintillator 1. In this case, when one radiation detector RD1 is arranged side by side with another radiation detector RD1 in the second direction D2, the light reflector 47 of the one radiation detector RD1 improves the reflectance of scintillation light at the other side surface 1d that faces the side surface 1c of the other radiation detector RD1 in the second direction D2. The other side surface 1d of the other radiation detector RD1 has high reflectance to scintillation light even in a configuration in which the light reflector 47 is not provided. Therefore, this configuration simplifies the configuration of the radiation detector RD1.

[0203] In the radiation detector RD1, the thickness of the light reflector is 0.05 to 100 μm. In this case, the reflectance of the scintillation light at the other side surface 1d is reliably improved, and therefore, this configuration reliably simplifies the configuration of the radiation detector RD1.

[0204] In the radiation detector RD1, the wiring member 30 is disposed on the same side as the scintillator 1 with respect to the semiconductor substrate 11. In this case, for example, there is no need to prepare a new substrate for connecting the wiring member 30 to the first and second electrodes 17, 18 by die bonding. Therefore, this configuration more reliably simplifies the configuration of the radiation detector. A configuration in which the wiring member 30 is arranged on the same side of the semiconductor substrate 11 as the scintillator 1 improves the space efficiency of the radiation detector RD1 compared to a configuration in which the wiring member 30 is arranged on the opposite side of the semiconductor substrate 11 from the scintillator 1.

[0205] In the radiation detector RD1, the wiring member 30 and the semiconductor substrate 11 have flexibility. The flexibility of the wiring member 30 is greater than the flexibility of the semiconductor substrate 11. In this case, vibrations are less likely to be transmitted from the wiring member 30 to the semiconductor substrate 11. Force is less likely to be applied to the semiconductor substrate 11 from the wiring member 30, and the semiconductor substrate 11 is less likely to be physically damaged. Therefore, this configuration reliably maintains the mechanical strength of the radiation detector RD1.

[0206] Second Embodiment The configuration of a radiation detector RD2 according to the second embodiment will be described with reference to Figures 24 and 25. In the description of radiation detector RD2, differences from the above-described radiation detector RD1 will be mainly described, and a description of common points may be omitted.

[0207] 24 is a perspective view showing a radiation detector RD2 according to a second embodiment. The radiation detector RD2 includes a scintillator 1, a first semiconductor photodetector element 10a, a second semiconductor photodetector element 10b, a first wiring member 30a, and a second wiring member 30b. The first and second semiconductor photodetector elements 10a, 10b detect scintillation light generated in the scintillator 1. The first semiconductor photodetector element 10a has a first semiconductor substrate 11a and is electrically connected to the first wiring member 30a. The second semiconductor photodetector element 10b has a second semiconductor substrate 11b and is electrically connected to the second wiring member 30b.

[0208] The scintillator 1 according to this embodiment has a pair of end faces 1a, 1b facing each other, a pair of side faces 1c, 1d facing each other, and a pair of side faces 1e, 1f facing each other. In this embodiment, the length of the side face 1c in the first direction D1 is greater than the width of the side face 1c in the third direction D3, and the length of the side face 1e in the first direction D1 is greater than the width of the side face 1e in the second direction D2. The length of the scintillator 1 in the first direction D1 is greater than the length of the scintillator 1 in the second direction D2 and the length of the scintillator 1 in the third direction D3. The first direction D1 is the longitudinal direction of the scintillator 1. The second direction D2 is perpendicular to the side face 1c, and the third direction D3 is perpendicular to the side face 1e. For example, when the side face 1c constitutes the first side face, the side face 1e constitutes the second side face.

[0209] The end faces 1a and 1b extend in the second direction D2. The end faces 1a and 1b also extend in the third direction D3. The end faces 1a and 1b, the side faces 1c and 1d, and the side faces 1e and 1f have a rectangular shape when viewed from a direction perpendicular to these faces. The scintillator 1 has a rectangular shape when viewed from the second direction D2 and the third direction D3. The scintillator 1 also has a rectangular shape when viewed from the first direction D1. In this embodiment, the scintillator 1 has a rectangular parallelepiped shape.

[0210] At least one of the end faces 1a, 1b is, for example, rough-finished. Therefore, at least one of the end faces 1a, 1b has a triangular wave-shaped cross section. At least one of the end faces 1a, 1b is, for example, a rough surface. The end faces 1a, 1b may be mirror-finished.

[0211] The first semiconductor substrate 11a is disposed so as to face the side surface 1c. The second semiconductor substrate 11b is disposed so as to face the side surface 1e. The side surface 1e is adjacent to the side surface 1c. The first semiconductor substrate 11a has, for example, the same shape and function as the semiconductor substrate 11 according to the first embodiment. The second semiconductor substrate 11b has, for example, the same shape and function as the first semiconductor substrate 11a disposed on the side surface 1c, except that it is disposed on the side surface 1e. The first semiconductor substrate 11a is disposed on the first side surface 1c, for example, via an adhesive. The second semiconductor substrate 11b is disposed on the second side surface 1e, for example, via an adhesive.

[0212] The first semiconductor substrate 11a and the second semiconductor substrate 11b have a first portion 21 and a second portion 22. In this embodiment, the first portion 21 of the first semiconductor substrate 11a is covered by the first side surface 1c. The second portion 22 of the first semiconductor substrate 11a is aligned with the first portion 21 of the first semiconductor substrate 11a in the first direction D1 and is exposed from the first side surface 1c. The first portion 21 of the second semiconductor substrate 11b is covered by the second side surface 1e. The second portion 22 of the second semiconductor substrate 11b is aligned with the first portion 21 of the second semiconductor substrate 11b in the first direction D1 and is exposed from the second side surface 1e.

[0213] A plurality of photodetection regions 23a, 23b, 23c, and 23d are arranged in the first portion 21. In this embodiment, four photodetection regions 23a, 23b, 23c, and 23d are arranged. The photodetection regions 23a, 23b, 23c, and 23d are aligned in the first direction D1. Each of the photodetection regions 23a, 23b, 23c, and 23d includes a plurality of avalanche photodiodes 12 and a plurality of quenching resistors 13. One photodetector unit 15 includes one avalanche photodiode 12 and one quenching resistor 13 electrically connected in series with the corresponding avalanche photodiode 12. A plurality of photodetector units 15 are arranged in the first portion 21.

[0214] The second portion 22 is provided with first electrodes 17a, 17b, 17c, and 17d and a second electrode 18. A plurality of quenching resistors 13 are electrically connected in parallel to the first electrodes 17a, 17b, 17c, and 17d via conductors 14a, 14b, 14c, and 14d, respectively. The plurality of quenching resistors 13 are electrically connected in series to one of the anodes and cathodes of corresponding ones of the plurality of avalanche photodiodes 12. The second electrode 18 is electrically connected in parallel to the other of the anodes and cathodes of the plurality of avalanche photodiodes 12 via conductor 14e.

[0215] The first wiring member 30a is arranged on the same side of the first semiconductor substrate 11a as the scintillator 1. The second wiring member 30b is arranged on the same side of the second semiconductor substrate 11b as the scintillator 1. The first wiring member 30a has, for example, the same shape and function as the wiring member 30 according to the first embodiment. The second wiring member 30b has, for example, the same shape and function as the first wiring member 30a electrically connected to the first semiconductor substrate 11a, except that it is electrically connected to the second semiconductor substrate 11b.

[0216] The first and second wiring members 30a, 30b have conductors 31a, 31b, 31c, 31d and a conductor 32. The conductors 31a, 31b, 31c, 31d are electrically connected to the first electrodes 17a, 17b, 17c, 17d, and the conductor 32 is connected to the second electrode 18. The first wiring member 30a and the second wiring member 30b and the first semiconductor substrate 11a and the second semiconductor substrate 11b are flexible. The flexibility of the first wiring member 30a is greater than that of the first semiconductor substrate 11a. The flexibility of the second wiring member 30b is greater than that of the second semiconductor substrate 11b.

[0217] When viewed from the second direction D2, one region formed by the outlines of the multiple photodetection regions 23a, 23b, 23c, and 23d of the first semiconductor substrate 11a has a shape corresponding to the outline shape of the first side surface 1c. The photodetectors 15 are arranged such that the photodetection regions 23a, 23b, 23c, and 23d have an outline shape corresponding to the outline shape of the first side surface 1c when viewed from the second direction D2. In this embodiment, when viewed from the second direction D2, the outline shape of the first side surface 1c is rectangular, and one region formed by the outlines of the multiple photodetection regions 23a, 23b, 23c, and 23d has a rectangular outline shape corresponding to the outline shape of the first side surface 1c.

[0218] When viewed from the third direction D3, one region formed by the outlines of the multiple photodetection regions 23a, 23b, 23c, and 23d of the second semiconductor substrate 11b has a shape corresponding to the outline shape of the second side surface 1e. The photodetectors 15 are arranged such that the photodetection regions 23a, 23b, 23c, and 23d have an outline shape corresponding to the outline shape of the second side surface 1e when viewed from the third direction D3. In this embodiment, when viewed from the third direction D3, the outline shape of the second side surface 1e is rectangular, and one region formed by the outlines of the multiple photodetection regions 23a, 23b, 23c, and 23d has a rectangular outline shape corresponding to the outline shape of the second side surface 1e.

[0219] In the first and second semiconductor substrates 11a and 11b, the photodetection regions 23a, 23b, 23c, and 23d are arranged, for example, in the first direction D1. In this embodiment, the photodetection regions 23a, 23b, 23c, and 23d are arranged in this order. The photodetection region 23d is closer to the second portion than the photodetection regions 23a, 23b, and 23c. The photodetection region 23c is closer to the second portion than the photodetection regions 23a and 23b. The photodetection region 23b is closer to the second portion than the photodetection region 23a. In this embodiment, the width of the conductive wire 14a is larger than the widths of the conductive wires 14b, 14c, and 14d. The width of the conductive wire 14b is larger than the widths of the conductive wires 14c and 14d. The width of the conductive wire 14c is larger than the width of the conductive wire 14d. For example, when the photodetection region 23a constitutes a first photodetection region, the photodetection region 23d constitutes a second photodetection region.

[0220] The radiation detector RD2 includes a first base 40a and a second base 40b. The first base 40a is disposed such that the first semiconductor substrate 11a is located between the first base 40a and the scintillator 1. The second base 40b is disposed such that the second semiconductor substrate 11b is located between the second base 40b and the scintillator 1. The first base 40a has, for example, the same shape and function as the base 40 according to the first embodiment. The second base 40b has, for example, the same shape and function as the first base 40a.

[0221] The first base 40a and the second base 40b each have a third portion 51 and a fourth portion 52. The third portion 51 of the first base 40a is covered with the first semiconductor substrate 11a. The fourth portion 52 of the first base 40a is aligned with the third portion 51 of the first base 40a in the first direction D1 and is exposed from the first semiconductor substrate 11a. The third portion 51 of the second base 40b is covered with the second semiconductor substrate 11b. The fourth portion 52 of the second base 40b is aligned with the third portion 51 of the second base 40b in the first direction D1 and is exposed from the second semiconductor substrate 11b.

[0222] The fourth portion 52 of the first base 40a and the second base 40b includes first terminals 41a, 41b, 41c, and 41d and a second terminal 42. The first terminals 41a, 41b, 41c, and 41d and the second terminal 42 of the first base 40a are disposed on the same side of the first semiconductor substrate 11a as the scintillator 1, for example. The first terminals 41a, 41b, 41c, and 41d and the second terminal 42 of the second base 40b are disposed on the same side of the second semiconductor substrate 11b as the scintillator 1, for example. The first terminals 41a, 41b, 41c, and 41d of the first base 40a and the second base 40b are electrically connected to the first electrodes 17a, 17b, 17c, and 17d by first wires 43, and the second terminals 42 of the first base 40a and the second base 40b are electrically connected to the second electrode 18 by second wires 44. The radiation detector RD2 does not necessarily have to include either the first base 40a or the second base 40b, or does not necessarily have to include both the first base 40a and the second base 40b.

[0223] The radiation detector RD2 includes, for example, a resin 45. The first wire 43 and the second wire 44 are covered with, for example, the resin 45. The resin 45 covers the first wire 43 and the second wire 44 individually, or covers both the first wire 43 and the second wire 44. When the resin 45 covers the first wire 43 and the second wire 44 individually, the wires may be spaced apart from each other or connected to each other.

[0224] The radiation detector RD2 includes, for example, a first light reflector 47a and a second light reflector 47b. The first light reflector 47a is disposed such that the first semiconductor substrate 11a is located between the first light reflector 47a and the scintillator 1. The second light reflector 47b is disposed such that the second semiconductor substrate 11b is located between the second light reflector 47b and the scintillator 1. In a configuration in which the radiation detector RD2 includes the first base 40a, the first light reflector 47a is disposed such that the first semiconductor substrate 11a and the first base 40a are located between the first light reflector 47a and the scintillator 1. In this configuration, the scintillator 1, the first semiconductor substrate 11a, the first base 40a, and the first light reflector 47a are arranged in this order. In a configuration in which the radiation detector RD2 does not include the first base 40a, the scintillator 1, the first semiconductor substrate 11a, and the first light reflector 47a are arranged in this order. In a configuration in which radiation detector RD2 includes the second base 40b, the second light reflector 47b is disposed such that the second semiconductor substrate 11b and the second base 40b are located between the second light reflector 47b and the scintillator 1. In this configuration, the scintillator 1, the second semiconductor substrate 11b, the second base 40b, and the second light reflector 47b are arranged in this order. In a configuration in which radiation detector RD2 does not include the second base 40b, the scintillator 1, the second semiconductor substrate 11b, and the second light reflector 47b are arranged in this order. The radiation detector RD2 does not have to include either the first light reflector 47a or the second light reflector 47b.

[0225] The first and second light reflectors 47a and 47b are made of, for example, the same material as and have the same shape as the light reflector 47 according to the first embodiment. The first and second light reflectors 47a and 47b have a thickness of, for example, 0.05 to 100 μm.

[0226] 25 is a diagram showing the path of part of the scintillation light. In FIG. 25, the path of part of the scintillation light is shown when the scintillator 1 is viewed from the first direction D1. The scintillation light includes, for example, light L20 and light L21 that are incident on the side surface 1c from the generation point GP1. Light L20 is incident on the side surface 1c at an incident angle EA23, and light L21 is incident on the side surface 1c at an incident angle EA24. For example, the incident angle EA23 is smaller than the critical angle at the side surface 1c, and the incident angle EA24 is larger than the critical angle at the side surface 1c. In this embodiment, the first and second semiconductor photodetector elements 10a and 10b can be bonded to the scintillator 1 with adhesives having the same refractive index, so that the critical angle at the side surface 1e is equal to the critical angle at the side surface 1c.

[0227] As shown in FIG. 25, light L20 is incident on side surface 1c at an incident angle EA23 and passes through side surface 1c. Light L20 is detected by first semiconductor photodetector element 10a arranged on side surface 1c. Light L21 is incident on side surface 1c at an incident angle EA24 and is totally reflected by side surface 1c. Light L21 is difficult to detect by first semiconductor photodetector element 10a arranged on side surface 1c. However, after being totally reflected by side surface 1c, light L21 is incident on side surface 1e, for example. There are cases where the incident angle EA25 of light L21 incident on side surface 1e is smaller than the critical angle at side surface 1e. In this case, light L21 passes through side surface 1e and is detected by second semiconductor photodetector element 10b arranged on side surface 1e. In other words, even if the angle of incidence on side surface 1c exceeds the critical angle and the scintillation light is not detected by first semiconductor photodetector element 10a arranged on side surface 1c, the scintillation light is detected by one of photodetection regions 23a, 23b, 23c, and 23d of second semiconductor photodetector element 10b arranged on side surface 1e adjacent to side surface 1c, for example, photodetection region 23a.

[0228] For example, the incident angle EA25 is 90 degrees minus the incident angle EA24. For example, when the incident angle EA24 is 60 degrees or greater, the incident angle EA25 is 30 degrees or less. As described above, if the refractive index of the scintillator 1 is 1.8 and the refractive index of the adhesive that adheres the first and second semiconductor photodetector elements 10a and 10b to the side surfaces 1c and 1e, respectively, is 1.5, the critical angle at the side surfaces 1c and 1e is approximately 56.4 degrees. In this case, even if scintillation light with an incident angle EA24 of 60 degrees or greater is incident on the side surface 1c, it is totally reflected by the side surface 1c. However, when the scintillation light is incident on the side surface 1e adjacent to the side surface 1c, it passes through the side surface 1e and is detected by one of the photodetection regions 23a, 23b, 23c, and 23d of the second semiconductor photodetector element 10b arranged on the side surface 1e, for example, the photodetection region 23a. When the incident angle EA24 of the scintillation light is, for example, 50 degrees or less, the scintillation light passes through the side surface 1c and is detected by any one of the photodetection regions 23a, 23b, 23c, and 23d of the first semiconductor photodetector element 10a arranged on the side surface 1c. In this embodiment, for example, a signal processing circuit connected to the first and second wiring members 30a and 30b adds up the electrical signals output in response to the incidence of light on the photodetection regions 23a, 23b, 23c, and 23d.

[0229] A first modified example of the radiation detector RD2 according to the second embodiment will be described with reference to Fig. 26. Fig. 26 is a perspective view showing the radiation detector RD2 according to the first modified example of the second embodiment. The radiation detector RD2 according to this modified example has the same configuration as the radiation detector RD2 according to the second embodiment, except for the configurations of the scintillator 1 and the photodetection regions 23a, 23b, 23c, and 23d.

[0230] The scintillator 1 according to this modification has a pair of end faces 1a, 1b facing each other in a first direction D1, a pair of side faces 1c, 1d facing each other in a second direction D2, and a pair of side faces 1e, 1f facing each other in a third direction D3. The end faces 1a, 1b, side faces 1c, 1d, and side faces 1e, 1f form the outer surface of the scintillator 1. In this modification, unlike the second embodiment, the end face 1a is inclined with respect to the second direction D2. The end face 1a is also inclined with respect to the third direction D3. The end face 1b extends in the second direction D and the third direction D3. In this modification, the direction perpendicular to the side face 1c coincides with the second direction D2, and the direction perpendicular to the side face 1e coincides with the third direction D3. The first direction D1 is the longitudinal direction of the scintillator 1. When viewed from the first direction D1, the end faces 1a, 1b are rectangular. The scintillator 1 has, for example, a rectangular shape when viewed in the first direction D1.

[0231] When viewed from the second direction D2, the edge 2a of the side surface 1c on the end face 1a side is inclined with respect to the third direction D3, and the edge 2g of the side surface 1d on the end face 1a side is inclined with respect to the third direction D3. When viewed from the second direction D2, the edges 2a and 2g extend approximately parallel to each other. When viewed from the second direction D2, the edges 2a and 2g form an angle of 10 to 80 degrees counterclockwise with respect to the third direction D3, for example. When viewed from the second direction D2, the edge 2b of the side surface 1c on the end face 1b side and the edge 2h of the side surface 1d on the end face 1b side extend in the third direction D3.

[0232] The photodetection regions 23a, 23b, 23c, and 23d of the first semiconductor substrate 11a are aligned, for example, in the first direction D1. When viewed from the second direction D2, one region formed by the outlines of the multiple photodetection regions 23a, 23b, 23c, and 23d of the first semiconductor substrate 11a has a shape corresponding to the outline shape of the first side surface 1c. The photodetection region 23a has, for example, a triangular outline shape corresponding to the outline shape of the side surface 1c. The photodetection regions 23b, 23c, and 23d have, for example, a rectangular outline shape.

[0233] When viewed from the third direction D3, the edge 2i of the side surface 1e on the end face 1a side is inclined with respect to the second direction D2, and the edge 2j of the side surface 1f on the end face 1a side is inclined with respect to the second direction D2. The edges 2i and 2j extend substantially parallel to each other when viewed from the third direction D3. When the side surface 1f is viewed from the third direction D3, the edges 2i and 2j form an angle of 10 to 80 degrees, for example, clockwise, with respect to the second direction D2.

[0234] The photodetection regions 23a, 23b, 23c, and 23d of the second semiconductor substrate 11b are aligned, for example, in the first direction D1. A region formed by the outlines of the multiple photodetection regions 23a, 23b, 23c, and 23d of the second semiconductor substrate 11b has a shape corresponding to the outline shape of the second side surface 1e. The photodetection region 23a has, for example, a triangular outline shape corresponding to the outline shape of the second side surface 1e. The photodetection regions 23b, 23c, and 23d have, for example, a rectangular outline shape.

[0235] In this modified example, the length of side surface 1c in the first direction D1 is greater than the width of side surface 1c in the third direction D3, and the length of side surface 1e in the first direction D1 is greater than the width of side surface 1e in the second direction D2. The length of scintillator 1 in the first direction D1 is greater than the length of scintillator 1 in the second direction D2 and the length of scintillator 1 in the third direction D3. At least one of end surfaces 1a, 1b is, for example, roughened. Only end surface 1b may be roughened, and end surface 1a may not be roughened. Side surfaces 1c, 1e are, for example, mirror-finished.

[0236] In this modification, the end face 1a is inclined with respect to the second direction D2 and the third direction D3 so that the scintillation light is easily totally reflected toward the side faces 1c and 1e. Of the scintillation light, the light incident on the end face 1a is easily reflected by the end face 1a and then incident on the side faces 1c and 1e.

[0237] A second modified example of the radiation detector RD2 according to the second embodiment will be described with reference to Fig. 27. Fig. 27 is a perspective view showing the radiation detector RD2 according to the second modified example of the second embodiment. The radiation detector RD2 according to this modified example has the same configuration as the radiation detector RD2 according to the second embodiment, except for the configurations of the scintillator 1 and the photodetection regions 23a, 23b, and 23c.

[0238] The scintillator 1 according to this modification has a pair of end faces 1a, 1b facing each other in a first direction D1, a pair of side faces 1c, 1d facing each other in a second direction D2, and a pair of side faces 1e, 1f facing each other in a third direction D3. The end faces 1a, 1b, the side faces 1c, 1d, and the side faces 1e, 1f form the outer surface of the scintillator 1. Unlike the second embodiment, in this modification, the end faces 1a, 1b are inclined with respect to the second direction D2 and the third direction D3. In this modification, the direction perpendicular to the side face 1c coincides with the second direction D2, and the direction perpendicular to the side face 1e coincides with the third direction D3. The first direction D1 is the longitudinal direction of the scintillator 1. When viewed from the first direction D1, the end faces 1a, 1b have a rectangular shape. When viewed from the first direction D1, the scintillator 1 has a rectangular shape, for example.

[0239] When viewed from the second direction D2, the edge 2a of the side surface 1c on the end face 1a side is inclined with respect to the third direction D3, and the edge 2g of the side surface 1d on the end face 1a side is inclined with respect to the third direction D3. When viewed from the second direction D2, the edges 2a and 2g extend substantially parallel to each other. When viewed from the second direction D2, the edges 2a and 2g form an angle of 10 to 80 degrees, for example, counterclockwise, with the third direction D3.

[0240] When viewed from the second direction D2, an edge 2b of the side surface 1c on the end surface 1b side is inclined with respect to the third direction D3, and an edge 2h of the side surface 1d on the end surface 1b side is inclined with respect to the third direction D3. When viewed from the second direction D2, the edges 2b and 2h extend approximately parallel to each other. When viewed from the second direction D2, the edges 2b and 2h form an angle of 10 to 80 degrees, for example, clockwise, with the third direction D3. When viewed from the second direction D2, the side surfaces 1c and 1d are, for example, trapezoidal in shape.

[0241] The photodetection regions 23a, 23b, and 23c of the first semiconductor substrate 11a are aligned, for example, in the first direction D1. When viewed from the second direction D2, one area formed by the outlines of the multiple photodetection regions 23a, 23b, and 23c of the first semiconductor substrate 11a has a shape corresponding to the outline shape of the first side surface 1c. In this modification, when viewed from the second direction D2, the outline shape of the first side surface 1c is trapezoidal. When viewed from the second direction D2, one area formed by the outlines of the multiple photodetection regions 23a, 23b, and 23c of the first semiconductor substrate 11a has a trapezoid shape corresponding to the outline shape of the first side surface 1c.

[0242] When viewed from the third direction D3, the edge 2i of the side surface 1e on the end face 1a side is inclined with respect to the second direction D2, and the edge 2j of the side surface 1f on the end face 1a side is inclined with respect to the second direction D2. The edges 2i and 2j extend substantially parallel to each other when viewed from the third direction D3. When the side surface 1f is viewed from the third direction D3, the edges 2i and 2j form an angle of 10 to 80 degrees, for example, clockwise, with respect to the second direction D2.

[0243] When viewed from the third direction D3, the edge 2k of the side surface 1e on the end face 1b side is inclined with respect to the second direction D2, and the edge 2m of the side surface 1f on the end face 1b side is inclined with respect to the second direction D2. When viewed from the third direction D3, the edges 2k and 2m extend approximately parallel to each other. When the side surface 1f is viewed from the third direction D3, the edges 2k and 2m form an angle of 10 to 80 degrees, for example, counterclockwise, with respect to the second direction D2. When viewed from the third direction D3, the side surfaces 1e and 1f are, for example, trapezoidal in shape.

[0244] The photodetection regions 23a, 23b, and 23c of the second semiconductor substrate 11b are aligned, for example, in the first direction D1. When viewed from the third direction D3, one area formed by the outlines of the multiple photodetection regions 23a, 23b, and 23c of the second semiconductor substrate 11b has a shape corresponding to the outline shape of the second side surface 1e. In this modification, when viewed from the third direction D3, the outline shape of the second side surface 1e is trapezoidal. When viewed from the third direction D3, one area formed by the outlines of the multiple photodetection regions 23a, 23b, and 23c of the second semiconductor substrate 11b has a trapezoidal shape corresponding to the outline shape of the second side surface 1e.

[0245] In this modification, the length of side surface 1c in first direction D1 is greater than the width of side surface 1c in third direction D3, and the length of side surface 1e in first direction D1 is greater than the width of side surface 1e in second direction D2. The length of scintillator 1 in first direction D1 is greater than the length of scintillator 1 in second direction D2 and the length of scintillator 1 in third direction D3.

[0246] At least one of the end faces 1a, 1b is, for example, rough-finished. Therefore, at least one of the end faces 1a, 1b has a triangular wave-shaped cross section. At least one of the end faces 1a, 1b is, for example, rough. The end faces 1a, 1b may be mirror-finished. The side faces 1c, 1e are, for example, mirror-finished.

[0247] In this modification, the end faces 1a and 1b are inclined with respect to the second direction D2 and the third direction D3 so that the scintillation light is easily totally reflected toward the side faces 1c and 1e. Of the scintillation light, light incident on the end faces 1a and 1b is easily reflected by the end faces 1a and 1b and then incident on the side faces 1c and 1e.

[0248] A third modified example of the radiation detector RD2 according to the second embodiment will be described with reference to Fig. 28. Fig. 28 is a perspective view showing the radiation detector RD2 according to the third modified example of the second embodiment. The radiation detector RD2 according to this modified example has the same configuration as the radiation detector RD2 according to the second embodiment, except for the configurations of the scintillator 1 and the photodetection regions 23a, 23b, and 23c.

[0249] The scintillator 1 according to this modification has a pair of end faces 1a, 1b facing each other in a first direction D1, a pair of side faces 1c, 1d facing each other in a second direction D2, and a pair of side faces 1e, 1f facing each other in a third direction D3. The end faces 1a, 1b, the side faces 1c, 1d, and the side faces 1e, 1f form the outer surface of the scintillator 1. Unlike the second embodiment, in this modification, the end faces 1a, 1b are inclined with respect to the second direction D2 and the third direction D3. In this modification, the direction perpendicular to the side face 1c coincides with the second direction D2, and the direction perpendicular to the side face 1e coincides with the third direction D3. The first direction D1 is the longitudinal direction of the scintillator 1. When viewed from the first direction D1, the end faces 1a, 1b have a rectangular shape. When viewed from the first direction D1, the scintillator 1 has a rectangular shape, for example.

[0250] When viewed from the second direction D2, the edge 2a of the side surface 1c on the end face 1a side is inclined with respect to the third direction D3, and the edge 2g of the side surface 1d on the end face 1a side is inclined with respect to the third direction D3. When viewed from the second direction D2, the edges 2a and 2g extend substantially parallel to each other. When viewed from the second direction D2, the edges 2a and 2g form an angle of 10 to 80 degrees, for example, counterclockwise, with the third direction D3.

[0251] When viewed from the second direction D2, an edge 2b of the side surface 1c on the side of the end surface 1b is inclined with respect to the third direction D3, and an edge 2h of the side surface 1d on the side of the end surface 1b is inclined with respect to the third direction D3. When viewed from the second direction D2, the edges 2b and 2h extend substantially parallel to each other. When viewed from the second direction D2, the edges 2b and 2h form an angle of 10 to 80 degrees, for example, counterclockwise, with the third direction D3.

[0252] The photodetection regions 23a, 23b, and 23c of the first semiconductor substrate 11a are aligned, for example, in the first direction D1. When viewed from the second direction D2, one area formed by the outlines of the multiple photodetection regions 23a, 23b, and 23c of the first semiconductor substrate 11a has a shape corresponding to the outline shape of the first side surface 1c. In this modification, when viewed from the second direction D2, the outline shape of the side surface 1c is a parallelogram. When viewed from the second direction D2, one area formed by the outlines of the multiple photodetection regions 23a, 23b, and 23c of the first semiconductor substrate 11a has a parallelogram shape corresponding to the outline shape of the first side surface 1c.

[0253] When viewed from the third direction D3, the edge 2i of the side surface 1e on the end face 1a side is inclined with respect to the second direction D2, and the edge 2j of the side surface 1f on the end face 1a side is inclined with respect to the second direction D2. The edges 2i and 2j extend substantially parallel to each other when viewed from the third direction D3. When the side surface 1f is viewed from the third direction D3, the edges 2i and 2j form an angle of 10 to 80 degrees, for example, clockwise, with respect to the second direction D2.

[0254] When viewed from the third direction D3, the edge 2k of the side surface 1e on the end face 1b side is inclined with respect to the second direction D2, and the edge 2m of the side surface 1f on the end face 1b side is inclined with respect to the second direction D2. When viewed from the third direction D3, the edges 2k and 2m extend approximately parallel to each other. When the side surface 1f is viewed from the third direction D3, the edges 2k and 2m form an angle of 10 to 80 degrees, for example, clockwise, with respect to the second direction D2. When viewed from the third direction D3, the side surfaces 1e and 1f have, for example, a parallelogram shape.

[0255] The photodetection regions 23a, 23b, and 23c of the second semiconductor substrate 11b are aligned, for example, in the first direction D1. When viewed from the third direction D3, one area formed by the outlines of the multiple photodetection regions 23a, 23b, and 23c of the second semiconductor substrate 11b has a shape corresponding to the outline shape of the second side surface 1e. In this modification, when viewed from the third direction D3, the outline shape of the side surface 1e is a parallelogram. When viewed from the third direction D3, one area formed by the outlines of the multiple photodetection regions 23a, 23b, and 23c of the second semiconductor substrate 11b has a parallelogram shape corresponding to the outline shape of the second side surface 1e.

[0256] In this modification, the length of side surface 1c in the first direction D1 is greater than the width of side surface 1c in the third direction D3, and the length of side surface 1e in the first direction D1 is greater than the width of side surface 1e in the second direction D2. The length of scintillator 1 in the first direction D1 is greater than the length of scintillator 1 in the second direction D2 and the length of scintillator 1 in the third direction D3. End surfaces 1a and 1b do not need to be roughened. Side surfaces 1c and 1e are, for example, mirror-finished.

[0257] In this modification, the end faces 1a and 1b are inclined with respect to the second direction D2 and the third direction D3 so that the scintillation light is easily totally reflected toward the side faces 1c and 1e. Of the scintillation light, light incident on the end faces 1a and 1b is easily reflected by the end faces 1a and 1b and then incident on the side faces 1c and 1e, respectively.

[0258] A fourth modified example of the radiation detector RD2 according to the second embodiment will be described with reference to Fig. 29. Fig. 29 is a perspective view showing the radiation detector RD2 according to the fourth modified example of the second embodiment. The radiation detector RD2 according to this modified example has the same configuration as the radiation detector RD2 according to the second embodiment, except for the configuration of the scintillator 1.

[0259] As shown in FIG. 29 , the scintillator 1 according to this modification has a plurality of portions 1p, 1q, 1r, and 1s. The plurality of portions 1p, 1q, 1r, and 1s correspond to the plurality of photodetection regions 23a, 23b, 23c, and 23d, respectively. The portion 1p corresponds to the photodetection region 23a. The portion 1q corresponds to the photodetection region 23b. The portion 1r corresponds to the photodetection region 23c. The portion 1s corresponds to the photodetection region 23d. The plurality of portions 1p, 1q, 1r, and 1s are independent of each other. The scintillator 1 according to this modification has, for example, the same form and contains the same material as the scintillator 1 according to the eighth modification of the first embodiment. The radiation detector RD2 according to this modification includes, for example, a light reflecting member 24. The light reflecting member 24 is disposed, for example, between the plurality of portions 1p, 1q, 1r, and 1s.

[0260] In this modification, when viewed from the second direction D2, each of the multiple photodetection regions 23a, 23b, 23c, and 23d has a contour shape that corresponds to the contour shape of the coupling surface 3c of the corresponding portion 1p, 1q, 1r, or 1s among the multiple portions 1p, 1q, 1r, or 1s, which faces the first semiconductor substrate 11a. In this modification, when viewed from the second direction D2, the coupling surface 3c of the portions 1p, 1q, 1r, or 1s is rectangular, and the corresponding photodetection regions 23a, 23b, 23c, and 23d have a rectangular contour shape.

[0261] When viewed from the third direction D3, each of the multiple photodetection regions 23a, 23b, 23c, and 23d has a contour shape that corresponds to the contour shape of the coupling surface 3e of the corresponding one of the multiple portions 1p, 1q, 1r, and 1s, which faces the second semiconductor substrate 11b. In this modification, when viewed from the third direction D3, the coupling surface 3e of the portions 1p, 1q, 1r, and 1s is rectangular, and the corresponding photodetection regions 23a, 23b, 23c, and 23d have a rectangular contour shape.

[0262] In the above, in this modified example, the scintillator 1 having the multiple portions 1p, 1q, 1r, and 1s has the same rectangular parallelepiped shape as the scintillator 1 of the second embodiment. In this modified example, at least one of the pair of opposing surfaces 3a, 3b may be inclined with respect to the second direction D2. The scintillator 1 having the multiple portions 1p, 1q, 1r, and 1s may have the same shape as the scintillators 1 of the first to third modified examples of the second embodiment. When the scintillator 1 of this modified example has the same shape as the scintillator 1 of the first to third modified examples of the second embodiment, the scintillation light generated in the portions 1p, 1q, 1r, and 1s can each take the following paths.

[0263] When the scintillator 1 having the multiple portions 1p, 1q, 1r, and 1s has the same configuration as the scintillator 1 of the first modified example of the second embodiment, for example, the facing surface 3a of the portion 1p is inclined with respect to the second direction D2. The scintillation light incident on the facing surface 3a of the portion 1p is likely to be incident on the connecting surfaces 3c and 3e of the portion 1p. The scintillation light incident on the connecting surfaces 3c and 3e of the portion 1p is detected in the light detection region 23a.

[0264] When the scintillator 1 of this modification has the same configuration as the scintillator 1 of the second modification of the second embodiment, it has three portions 1p, 1q, and 1r. The portion 1p corresponds to the photodetection region 23a. The portion 1q corresponds to the photodetection region 23b. The portion 1r corresponds to the photodetection region 23c. In this case, the facing surface 3a of the portion 1p is inclined with respect to the second direction D2. Scintillation light incident on the facing surface 3a is likely to be incident on the coupling surfaces 3c and 3e of the portion 1p. Scintillation light incident on the coupling surfaces 3c and 3e of the portion 1p is detected in the photodetection region 23a. The facing surface 3b of the portion 1r is inclined with respect to the second direction D2. Scintillation light incident on the facing surface 3b of the portion 1r is likely to be incident on the coupling surfaces 3c and 3e of the portion 1r. Scintillation light incident on the coupling surfaces 3c and 3e of the portion 1r is detected in the photodetection region 23c.

[0265] When the scintillator 1 of this modification has the same configuration as the scintillator 1 of the third modification of the second embodiment, it has three portions 1p, 1q, and 1r. The portion 1p corresponds to the photodetection region 23a. The portion 1q corresponds to the photodetection region 23b. The portion 1r corresponds to the photodetection region 23c. In this case, the facing surface 3a of the portion 1p is inclined with respect to the second direction D2. Scintillation light incident on the facing surface 3a of the portion 1p is likely to be incident on the coupling surfaces 3c and 3e of the portion 1p. Scintillation light incident on the coupling surfaces 3c and 3e of the portion 1p is detected in the photodetection region 23a. The facing surface 3b of the portion 1r is inclined with respect to the second direction D2. Scintillation light incident on the facing surface 3b is likely to be incident on the coupling surfaces 3c and 3e of the portion 1r. Scintillation light incident on the coupling surfaces 3c and 3e of the portion 1r is detected in the photodetection region 23c.

[0266] As described above, the radiation detector RD2 has a rectangular shape when viewed from the first direction D1, and includes a scintillator 1 having a pair of end faces 1a, 1b facing each other in the first direction D1, a first side face 1c connecting the pair of end faces 1a, 1b, and a second side face 1e connecting the pair of end faces 1a, 1b and adjacent to the side face 1c, a first semiconductor photodetector element 10a having a first semiconductor substrate 11a arranged to face the first side face 1c, a second semiconductor photodetector element 10b having a second semiconductor substrate 11b arranged to face the second side face 1e, a first wiring member 30a electrically connected to the first semiconductor photodetector element 10a, and a second wiring member 30b electrically connected to the second semiconductor photodetector element 10b. The length of the scintillator 1 in the first direction D1 is greater than the length of the scintillator 1 in the second direction D2 perpendicular to the first side face 1c and the length of the scintillator 1 in the third direction D3 perpendicular to the second side face 1e. The length of the first side surface 1c in the first direction D1 is greater than the width of the first side surface 1c in the third direction D3. The length of the second side surface 1e in the first direction D1 is greater than the width of the second side surface 1e in the second direction D2. The first semiconductor substrate 11a and the second semiconductor substrate 11b are covered by either the corresponding first side surface 1c or second side surface 1e and have a first portion 21 in which multiple photodetection regions 23a, 23b, 23c, and 23d are arranged, and a second portion 22 aligned with the first portion 21 in the first direction D1 and exposed from either the corresponding first side surface 1c or second side surface 1e. The multiple photodetection regions 23a, 23b, 23c, and 23d are aligned in the first direction D1 and each include at least one avalanche photodiode 12 operating in Geiger mode and at least one quenching resistor 13 electrically connected in series with one of the anode and cathode of the corresponding one of the at least one avalanche photodiode 12.The second portion 22 is provided with a plurality of first electrodes 17a, 17b, 17c, and 17d electrically connected to at least one quenching resistor 13 included in a corresponding one of the plurality of photodetection regions 23a, 23b, 23c, and 23d, and a second electrode 18 electrically connected to the other of the anode and the cathode of each avalanche photodiode. The first wiring member 30a and the second wiring member 30b have a plurality of conductors 31a, 31b, 31c, and 31d electrically connected to the corresponding one of the plurality of first electrodes 17a, 17b, 17c, and 17d, and a conductor 32 connected to the second electrode 18.

[0267] In this embodiment, the radiation detector RD2 includes a scintillator 1 that is long in the first direction D1 and a first semiconductor photodetecting element 10a that is arranged on a first side surface 1c of the scintillator 1. The first semiconductor photodetecting element 10a detects not only scintillation light that is directly incident on the first side surface 1c on which the first semiconductor photodetecting element 10a is arranged, but also scintillation light that is reflected by a side surface 1d that faces the first side surface 1c on which the first semiconductor photodetecting element 10a is arranged and then incident on the first side surface 1c. Because the length of the scintillator 1 in the second direction D2 is shorter than the length of the scintillator 1 in the first direction D1, the scintillation light that is directly incident on the first side surface 1c and the scintillation light that is reflected by the side surface 1d and then incident on the first side surface 1c are detected by the first semiconductor photodetecting element 10a with a small time difference. Therefore, the radiation detector RD2 achieves high time resolution. According to radiation detector RD2, even if the angle of incidence of scintillation light on first side surface 1c exceeds the critical angle at first side surface 1c and the scintillation light is not detected by first semiconductor photodetector element 10a arranged on first side surface 1c, the scintillation light is detected by second semiconductor photodetector element 10b arranged on second side surface 1e adjacent to first side surface 1c. Therefore, radiation detector RD2 realizes a radiation detector having high time resolution and reliably improves the amount of scintillation light received by first and second semiconductor photodetector elements 10a, 10b. The radiation detector RD2 includes first and second semiconductor photodetector elements 10a and 10b, each having a plurality of photodetection regions 23a, 23b, 23c, and 23d arranged in a first direction D1. For example, the distance in the first direction D1 between the point of generation of scintillation light and one end surface 1a of the scintillator 1 can be determined from the position of the photodetection region 23a, 23b, 23c, and 23d that detects the most scintillation light among the plurality of photodetection regions 23a, 23b, 23c, and 23d. As a result, the magnitude of the energy of the radiation incident on the scintillator 1 can be accurately measured. Therefore, the radiation detector RD2 achieves high energy resolution.

[0268] In the radiation detector RD2, at least one of the pair of end faces 1a and 1b is inclined with respect to the second direction D2. In this case, the scintillation light is more reliably incident on the first side surface 1c and the second side surface 1e that face the first and second semiconductor substrates 11a, 11b. Since the number of times that the scintillation light is reflected by the end surfaces 1a, 1b or the side surfaces is reduced and the return attenuation is also reduced, the radiation detector RD2 more reliably improves the amount of light received by the first and second semiconductor photodetector elements 10a, 10b.

[0269] In the radiation detector RD2, of the pair of end faces 1a, 1b, the end faces 1a, 1b extending in the second direction D2 have a triangular wave shape in cross section. In this case, the scintillation light is more reliably incident on the first side surface 1c and the second side surface 1e that face the first and second semiconductor substrates 11a, 11b. Since the number of times that the scintillation light is reflected by the end surfaces 1a, 1b or the side surfaces is reduced and the return attenuation is also reduced, the radiation detector RD2 more reliably improves the amount of light received by the first and second semiconductor photodetector elements 10a, 10b. When the cross sections of the end faces 1a, 1b have a triangular wave shape, the amount of light received by the first and second semiconductor photodetector elements 10a, 10b is more reliably improved without tilting the end faces 1a, 1b with respect to the second direction D2. In a configuration in which the end faces 1a, 1b extend in the second direction D2, the radiation detector RD2 can be manufactured using less scintillator 1 than in a configuration in which the end faces 1a, 1b are tilted with respect to the second direction D2.

[0270] In the radiation detector RD2, of the pair of end faces 1a, 1b, the end faces 1a, 1b extending in the second direction D2 are rough surfaces. In this case, the scintillation light is more reliably incident on the first side surface 1c and the second side surface 1e that face the first and second semiconductor substrates 11a, 11b. Since the number of times that the scintillation light is reflected by the end surfaces 1a, 1b or the side surfaces is reduced and the return attenuation is also reduced, the radiation detector RD2 more reliably improves the amount of light received by the first and second semiconductor photodetector elements 10a, 10b. When the cross sections of the end faces 1a, 1b are rough, the amount of light received by the first and second semiconductor photodetector elements 10a, 10b is more reliably improved even if the end faces 1a, 1b are not inclined with respect to the second direction D2. In a configuration in which the end faces 1a, 1b extend in the second direction D2, the radiation detector RD2 can be manufactured using less scintillator 1 than in a configuration in which the end faces 1a, 1b are inclined with respect to the second direction D2.

[0271] In the radiation detector RD2, when viewed from the second direction D2, one region formed by the outlines of the multiple photodetection regions 23a, 23b, 23c, and 23d has a shape corresponding to the outline shape of the first side surface 1c. When viewed from the third direction D3, one region formed by the outlines of the multiple photodetection regions 23a, 23b, 23c, and 23d has a shape corresponding to the outline shape of the second side surface 1e. In this case, the photodetection regions 23a, 23b, 23c, and 23d do not need to be disposed in locations on the first and second semiconductor substrates 11a and 11b that cannot receive scintillation light, thereby suppressing increases in dark count and capacitance in the photodetection regions 23a, 23b, 23c, and 23d. Therefore, this configuration reliably improves the time resolution and energy resolution of the first and second semiconductor photodetector elements 10a and 10b.

[0272] In radiation detector RD2, scintillator 1 has a plurality of independent portions 1p, 1q, 1r, and 1s corresponding to each of the plurality of photodetection regions 23a, 23b, 23c, and 23d. Each of the plurality of portions 1p, 1q, 1r, and 1s has a pair of opposing surfaces 3a and 3b facing each other in first direction D1, a first coupling surface 3c connecting the pair of opposing surfaces 3a and 3b and facing first semiconductor substrate 11a, and a second coupling surface 3e connecting the pair of opposing surfaces 3a and 3b, facing second semiconductor substrate 11b, and adjacent to first coupling surface 3c. In this case, the scintillation light generated in each of the portions 1p, 1q, 1r, and 1s is confined within the portion 1p, 1q, 1r, and 1s. The photodetection regions 23a, 23b, 23c, and 23d corresponding to the portions 1p, 1q, 1r, and 1s reliably detect the scintillation light generated within the portions 1p, 1q, 1r, and 1s. Therefore, the radiation detector RD2 reliably achieves high energy resolution.

[0273] In the radiation detector RD2, the multiple portions 1p, 1q, 1r, and 1s are joined to one another. In this case, the physical strength of the scintillator 1 is improved, and therefore the radiation detector RD2 more reliably achieves high energy resolution.

[0274] The radiation detector RD2 may further include a light reflecting member 24. The light reflecting member 24 is disposed between the plurality of portions 1p, 1q, 1r, and 1s. In this case, the scintillation light generated in each of the portions 1p, 1q, 1r, and 1s is reliably confined within the portions 1p, 1q, 1r, and 1s. The photodetection regions 23a, 23b, 23c, and 23d corresponding to the portions 1p, 1q, 1r, and 1s more reliably detect the scintillation light generated within the portions 1p, 1q, 1r, and 1s. Therefore, the radiation detector RD2 more reliably achieves high energy resolution.

[0275] In the radiation detector RD2, at least one of the pair of opposing surfaces 3a, 3b is inclined with respect to the second direction D2. In this case, the scintillation light is more reliably incident on the coupling surfaces 3c, 3e. Since the number of times the scintillation light is reflected by the opposing surfaces 3a, 3b or the coupling surfaces is reduced and the return loss is also reduced, this configuration more reliably improves the amount of light received by the first and second semiconductor photodetector elements 10a, 10b.

[0276] In the radiation detector RD2, of the pair of opposing surfaces 3a, 3b, the opposing surfaces 3a, 3b extending in the second direction D2 have a triangular wave shape in cross section. In this case, the scintillation light is more reliably incident on the coupling surfaces 3c, 3e. Since the number of times the scintillation light is reflected by the opposing surfaces 3a, 3b or the coupling surfaces is reduced and the return loss is also reduced, this configuration more reliably improves the amount of light received by the first and second semiconductor photodetector elements 10a, 10b.

[0277] In the radiation detector RD2, of the pair of opposing surfaces 3a, 3b, the opposing surfaces 3a, 3b extending in the second direction D2 are rough surfaces. In this case, the scintillation light is more reliably incident on the coupling surfaces 3c, 3e. Since the number of times the scintillation light is reflected by the opposing surfaces 3a, 3b or the coupling surfaces is reduced and the return loss is also reduced, this configuration more reliably improves the amount of light received by the first and second semiconductor photodetector elements 10a, 10b.

[0278] In the radiation detector RD2, when viewed from the second direction D2, each of the multiple photodetection regions 23a, 23b, 23c, and 23d has a contour shape that corresponds to the contour shape of the first coupling surface 3c of the corresponding portion 1p, 1q, 1r, and 1s of the multiple portions 1p, 1q, 1r, and 1s that faces the first semiconductor substrate 11a. When viewed from the third direction D3, each of the multiple photodetection regions 23a, 23b, 23c, and 23d has a contour shape that corresponds to the contour shape of the second coupling surface 3e of the corresponding portion 1p, 1q, 1r, and 1s of the multiple portions 1p, 1q, 1r, and 1s that faces the second semiconductor substrate 11b. In this case, the photodetection regions 23a, 23b, 23c, and 23d do not need to be disposed in locations on the first and second semiconductor substrates 11a and 11b that cannot receive scintillation light, thereby suppressing increases in dark count and capacitance in the photodetection regions 23a, 23b, 23c, and 23d. Therefore, this configuration reliably improves the time resolution and energy resolution of the first and second semiconductor photodetector elements 10a and 10b.

[0279] In the radiation detector RD2, the multiple photodetection regions 23a, 23b, 23c, and 23d include a first photodetection region 23a and a second photodetection region 23d that is closer to the second portion 22 than the first photodetection region 23a. The width of the conductive wire 14a that electrically connects the first electrode 17a corresponding to the first photodetection region 23a to the first photodetection region 23a is greater than the width of the conductive wire 14d that electrically connects the first electrode 17d corresponding to the second photodetection region 23d to the second photodetection region 23d. In this case, the difference in electrical resistance between the conductor 14a electrically connecting the first electrode 17a corresponding to the first photodetection region 23a to the first photodetection region 23a and the conductor 14d electrically connecting the first electrode 17d corresponding to the second photodetection region 23d to the second photodetection region 23d is reduced. The length of the conductor 14a electrically connecting the first electrode 17a corresponding to the first photodetection region 23a to the first photodetection region 23a is longer than the length of the conductor 14d electrically connecting the first electrode 17d corresponding to the second photodetection region 23d to the second photodetection region 23d. The longer the conductors 14a and 14d, the higher the electrical resistance of the conductors 14a and 14d. Therefore, in a configuration in which the width of the long conductor 14a is larger than the width of the short conductor 14d, the difference in electrical resistance between the long conductor 14a and the short conductor 14d is reduced. Therefore, this configuration more reliably improves the time resolution and energy resolution of the radiation detector RD2.

[0280] The radiation detector RD2 further includes a first base 40a arranged such that the first semiconductor substrate 11a is located between the first base 40a and the scintillator 1, and a second base 40b arranged such that the second semiconductor substrate 11b is located between the first base 40a and the scintillator 1. The first base 40a and the second base 40b each have a third portion covered with the first semiconductor substrate 11a and the second semiconductor substrate 11b, and a fourth portion aligned with the third portion in the first direction D1 and exposed from the first semiconductor substrate 11a and the second semiconductor substrate 11b. Each fourth portion includes first terminals 41a, 41b, 41c, 41d and a second terminal 42 arranged on the same side as the scintillator 1 with respect to the corresponding first semiconductor substrate 11a or second semiconductor substrate 11b. The first terminals 41a, 41b, 41c, and 41d are electrically connected to the first electrodes 17a, 17b, 17c, and 17d by first wires 43, and the second terminal 42 is electrically connected to the second electrode 18 by a second wire 44. In this case, the mechanical strength of the radiation detector RD2 is reinforced. Therefore, this configuration reliably realizes a radiation detector RD2 with reinforced mechanical strength.

[0281] In the radiation detector RD2, the first wire 43 and the second wire 44 are covered with a resin 45. In this case, the resin 45 protects the first and second wires 43, 44, making it difficult for the first and second wires 43, 44 to be damaged. Therefore, this configuration suppresses deterioration of the electrical connection between the first and second terminals 41, 42 and the first and second electrodes 17, 18.

[0282] The radiation detector RD2 further includes a first light reflector 47a arranged so that the first semiconductor substrate 11a is located between the first light reflector 47a and the scintillator 1, and a second light reflector 47b arranged so that the second semiconductor substrate 11b is located between the first light reflector 47a and the scintillator 1. In this case, when one radiation detector RD2 and another radiation detector RD2 are aligned in the second direction D2, the first light reflector 47a improves the reflectance of scintillation light on the other side surface 1d of the radiation detector RD2 adjacent to each other in the second direction D2. The other side surface 1d of the other radiation detector RD2 has high reflectance to scintillation light even in a configuration in which the first light reflector 47a is not provided. When one radiation detector RD2 and another radiation detector RD2 are aligned in the third direction D3, the second light reflector 47b improves the reflectance of scintillation light on the other side surface 1f of the radiation detector RD2 adjacent to each other in the third direction D3. The other side surface 1f of the other radiation detector RD2 has high reflectance to scintillation light even in a configuration in which the second light reflector 47b is not provided. Therefore, this configuration reliably simplifies the configuration of the radiation detector RD2.

[0283] In the radiation detector RD2, the thickness of the first light reflector and the second light reflector is 0.05 to 100 μm. In this case, the reflectance of the scintillation light at the other side surfaces 1d and 1f is reliably improved, and therefore, this configuration reliably simplifies the configuration of the radiation detector RD2.

[0284] In the radiation detector RD2, the first wiring member 30a is arranged on the same side of the first semiconductor substrate 11a as the scintillator 1. The second wiring member 30b is arranged on the same side of the second semiconductor substrate 11b as the scintillator 1. In this case, for example, there is no need to prepare a new substrate for connecting the first and second wiring members 30a, 30b to the first and second electrodes 17, 18, respectively, by die bonding. Therefore, this configuration more reliably simplifies the configuration of the radiation detector RD2. A configuration in which the first and second wiring members 30a, 30b are arranged on the same side as the scintillator 1 with respect to the first and second semiconductor substrates 11a, 11b, respectively, improves the space efficiency of the radiation detector RD2 compared to a configuration in which the first and second wiring members 30a, 30b are arranged on the opposite side of the scintillator 1 with respect to the first and second semiconductor substrates 11a, 11b, respectively.

[0285] In the radiation detector RD2, the first and second wiring members 30a and 30b and the first and second semiconductor substrates 11a and 11b are flexible. The flexibility of the first wiring member 30a is greater than that of the first semiconductor substrate 11a. The flexibility of the second wiring member 30b is greater than that of the second semiconductor substrate 11b. In this case, vibrations are less likely to be transmitted from the first and second wiring members 30a, 30b to the first and second semiconductor substrates 11a, 11b. Forces are less likely to be applied to the first and second semiconductor substrates 11a, 11b from the first and second wiring members 30a, 30b, respectively, and the first and second semiconductor substrates 11a, 11b are less likely to be physically damaged. Therefore, this configuration reliably maintains the mechanical strength of the radiation detector RD2.

[0286] (Third embodiment) The configuration of the radiation detector array RA1 according to the third embodiment will be described with reference to Fig. 30. Fig. 30 is a perspective view showing the radiation detector array RA1 according to the third embodiment. The radiation detector array RA1 is configured by arranging a plurality of radiation detectors RD1 according to the first embodiment in a two-dimensional matrix.

[0287] The plurality of radiation detectors RD1 are, for example, arranged in the second direction D2 and further arranged in the third direction D3. In the example shown in Fig. 30, six radiation detectors RD1 according to the eighth modified example of the first embodiment are lined up in the second direction D2, and six are also lined up in the third direction D3. The radiation detector array RA1 is composed of, for example, a total of 36 radiation detectors RD1.

[0288] The facing surface 3a of the portion 1p included in one radiation detector RD1 is flush with the facing surface 3a of the portion 1p included in another radiation detector RD1 adjacent to it in the second direction D2 or the third direction D3, for example. The semiconductor photodetector element 10 of one radiation detector RD1 is aligned with the semiconductor photodetector element 10 of another radiation detector RD1 adjacent to it in the third direction D3. The semiconductor photodetector elements 10 adjacent to each other in the third direction D3 are, for example, formed integrally with each other. The semiconductor photodetector elements 10 adjacent to each other in the third direction D3 do not have to be formed integrally with each other.

[0289] The radiation detector array RA1 may be configured with the radiation detector RD1 according to the first embodiment and any one of the first to seventh modifications of the first embodiment, in addition to the radiation detector RD1 according to the eighth modification of the first embodiment. In this case as well, the semiconductor photodetector element 10 of one radiation detector RD1 is aligned with the semiconductor photodetector element 10 of another radiation detector RD1 adjacent to it in the third direction D3. The semiconductor photodetector elements 10 adjacent to each other in the third direction D3 are, for example, formed integrally with each other. The semiconductor photodetector elements 10 adjacent to each other in the third direction D3 do not have to be formed integrally with each other.

[0290] As described above, the radiation detector array RA1 is a radiation detector array RA1 in which a plurality of radiation detectors RD1 are arranged two-dimensionally in a matrix when viewed from the first direction D1, and each of the plurality of radiation detectors RD1 is the radiation detector RD1 according to the first aspect, and the semiconductor photodetector element 10 of one radiation detector RD1 is aligned with the semiconductor photodetector element 10 of another radiation detector RD1 adjacent to it in a direction parallel to the side surface 1c.

[0291] According to this embodiment, a radiation detector array RA1 is realized in which radiation detectors RD1 having high time resolution and high energy resolution are arranged two-dimensionally in a matrix. Because one radiation detector RD1 is equipped with, for example, the light reflector 47, the other coupling surface 3d of another adjacent radiation detector RD1 has high reflectivity to scintillation light even if it is configured without the light reflector 47. Because the radiation detector RD1 is configured without the new light reflector 47 on the other coupling surface 3d, the distance between the radiation detectors RD1 in the second direction D2 in the radiation detector array RA1 is reduced.

[0292] In the radiation detector array RA1, the semiconductor photodetector elements 10 adjacent to each other in a direction parallel to the side surface 1c, that is, in the third direction D3, are formed integrally with each other. In this case, when manufacturing the radiation detector array RA1 in which a plurality of radiation detectors RD1 are two-dimensionally arranged in a matrix, the process of forming the semiconductor photodetector element 10 is simplified.

[0293] (Fourth embodiment) The configuration of a radiation detector array RA2 according to the fourth embodiment will be described with reference to Fig. 31. Fig. 31 is a perspective view showing the radiation detector array RA2 according to the fourth embodiment. The radiation detector array RA2 is configured by two-dimensionally arranging a plurality of radiation detectors RD2 according to the second embodiment in a matrix form.

[0294] The plurality of radiation detectors RD2 are, for example, arranged in the second direction D2 and further arranged in the third direction D3. In the example shown in Fig. 31, six radiation detectors RD2 according to the fourth modified example of the second embodiment are lined up in the second direction D2, and six are also lined up in the third direction D3. The radiation detector array RA2 is composed of, for example, a total of 36 radiation detectors RD1.

[0295] The facing surface 3a of the portion 1p included in one radiation detector RD2 is flush with the facing surface 3a of the portion 1p included in another radiation detector RD2 adjacent to it in the second direction D2 or the third direction D3, for example. The first semiconductor photodetecting element 10a of one radiation detector RD2 is aligned with the first semiconductor photodetecting element 10a of another radiation detector RD2 adjacent to it in the third direction D3. The second semiconductor photodetecting element 10b of one radiation detector RD2 is aligned with the second semiconductor photodetecting element 10b of yet another radiation detector RD2 adjacent to it in the second direction D2. The first semiconductor photodetecting elements 10a adjacent to each other in the third direction D3 are, for example, formed integrally with each other. The second semiconductor photodetecting elements 10b adjacent to each other in the second direction D2 are, for example, formed integrally with each other.

[0296] The radiation detector array RA2 may be configured with the radiation detector RD2 according to the second embodiment and any one of the first to third modifications of the second embodiment, in addition to the radiation detector RD2 according to the fourth modification of the second embodiment. In this case as well, the first semiconductor photodetecting element 10a of one radiation detector RD2 is aligned with the first semiconductor photodetecting element 10a of another radiation detector RD2 adjacent to it in the third direction D3. The second semiconductor photodetecting element 10b of one radiation detector RD2 is aligned with the second semiconductor photodetecting element 10b of yet another radiation detector RD2 adjacent to it in the second direction D2. The first semiconductor photodetecting elements 10a adjacent to each other in the third direction D3 are, for example, integrally formed with each other. The second semiconductor photodetecting elements 10b adjacent to each other in the second direction D2 are, for example, integrally formed with each other. The first semiconductor photodetecting elements 10a adjacent to each other in the third direction D3 do not have to be integrally formed with each other. The second semiconductor photodetecting elements 10b adjacent to each other in the second direction D2 do not have to be integrally formed with each other.

[0297] As described above, the radiation detector array RA2 is a radiation detector array RA2 in which a plurality of radiation detectors RD2 are arranged two-dimensionally in a matrix when viewed from the first direction D1, and each of the plurality of radiation detectors RD2 is the radiation detector RD2 according to the second aspect, and the first semiconductor photodetection element 10a of one radiation detector RD2 is aligned with the first semiconductor photodetection element 10a of another radiation detector RD2 adjacent to it in the third direction D3, and the second semiconductor photodetection element 10b of one radiation detector RD2 is aligned with the second semiconductor photodetection element 10b of yet another radiation detector RD2 adjacent to it in the second direction D2.

[0298] According to this embodiment, a radiation detector array RA2 is realized in which radiation detectors RD2 having high time resolution are arranged two-dimensionally in a matrix. Because one radiation detector RD2 is equipped with, for example, the first and second light reflectors 47a, 47b, the other coupling surfaces 3d, 3f of another adjacent radiation detector RD1 have high reflectivity to scintillation light even if the other coupling surfaces 3d, 3f do not have the first and second light reflectors 47a, 47b, respectively. Because the radiation detector RD2 is configured such that the first and second light reflectors 47a, 47b are not arranged on the other coupling surfaces 3d, 3f, the distance between the radiation detectors RD2 in the radiation detector array RA2 is reduced.

[0299] In the radiation detector array RA2, the first semiconductor photodetector elements 10a adjacent to each other in the third direction D3 are formed integrally with each other. In this case, when manufacturing a radiation detector array RA2 in which a plurality of radiation detectors RD2 are two-dimensionally arranged in a matrix, the process of forming the first semiconductor photodetector elements 10a is simplified.

[0300] In the radiation detector array RA2, the second semiconductor photodetector elements 10b adjacent to each other in the second direction D2 are formed integrally with each other. In this case, when manufacturing a radiation detector array RA2 in which a plurality of radiation detectors RD2 are two-dimensionally arranged in a matrix, the process of forming the second semiconductor photodetector elements 10b is simplified.

[0301] The above describes embodiments and modifications of the present invention, but the present invention is not necessarily limited to the above-described embodiments and modifications, and various modifications are possible without departing from the spirit of the present invention.

[0302] In the radiation detectors RD1 and RD2, the photodetection regions 23a, 23b, 23c, and 23d do not need to have a contour shape corresponding to the contour shape of the side surfaces 1c and 1e when viewed from the second direction D2. In a configuration in which the photodetection regions 23a, 23b, 23c, and 23d have a contour shape corresponding to the contour shape of the side surfaces 1c and 1e, as described above, the photodetection regions 23a, 23b, 23c, and 23d do not need to be disposed in locations on the semiconductor substrates 11, 11a, and 11b that cannot receive scintillation light, thereby suppressing increases in dark count and capacitance in the photodetection regions 23a, 23b, 23c, and 23d. Therefore, this configuration reliably improves the time resolution of the radiation detectors RD1 and RD2. The radiation detectors RD1 and RD2 do not necessarily have to include the light reflecting member 24. In a configuration in which the radiation detectors RD1 and RD2 include the light reflecting member 24, as described above, the scintillation light generated in each of the portions 1p, 1q, 1r, and 1s is reliably confined within the portions 1p, 1q, 1r, and 1s. The light detection regions 23a, 23b, 23c, and 23d corresponding to the portions 1p, 1q, 1r, and 1s more reliably detect the scintillation light generated within the portions 1p, 1q, 1r, and 1s. Therefore, the radiation detectors RD1 and RD2 more reliably achieve high time resolution. The width of the conductive wire 14a electrically connecting the first electrode 17a corresponding to the first photodetection region 23a to the first photodetection region 23a may be larger than the width of the conductive wire 14d electrically connecting the first electrode 17d corresponding to the second photodetection region 23d to the second photodetection region 23d. In a configuration in which the width of the conductive wire 14a electrically connecting the first electrode 17a corresponding to the first photodetection region 23a to the first photodetection region 23a is larger than the width of the conductive wire 14d electrically connecting the first electrode 17d corresponding to the second photodetection region 23d to the second photodetection region 23d, as described above, the difference in electrical resistance between the conductive wire 14a electrically connecting the first electrode 17a corresponding to the first photodetection region 23a to the first photodetection region 23a and the conductive wire 14d electrically connecting the first electrode 17d corresponding to the second photodetection region 23d to the second photodetection region 23d is reduced. The radiation detectors RD1 and RD2 do not necessarily have to include the bases 40, 40a, and 40b. When the radiation detectors RD1 and RD2 include the bases 40, 40a, and 40b, the mechanical strength of the semiconductor substrates 11, 11a, and 11b is reinforced, as described above. Therefore, the radiation detectors RD1 and RD2 reliably realize the semiconductor photodetector elements 10, 10a, and 10b with reinforced mechanical strength. The radiation detectors RD1 and RD2 do not necessarily have to include the resin 45. When the radiation detectors RD1 and RD2 are configured to include the resin 45, as described above, the first and second wires 43 and 44 are protected from damage. Therefore, the radiation detectors RD1 and RD2 reliably realize the semiconductor photodetector elements 10, 10a, and 10b with improved mechanical strength. The radiation detectors RD1, RD2 do not necessarily have to include the light reflectors 47, 47a, 47b. In a configuration in which the radiation detectors RD1, RD2 include the light reflectors 47, 47a, 47b, when one radiation detector RD1, RD2 is arranged next to the other radiation detector RD1, RD2, the light reflectors 47, 47a, 47b of the one radiation detector RD1, RD2 improve the reflectance of scintillation light on the other side surfaces 1d, 1f that face the side surfaces of the other radiation detectors RD1, RD2. Therefore, this configuration simplifies the configuration of the radiation detectors RD1, RD2. The wiring members 30, 30a, 30b do not have to be arranged on the same side of the semiconductor substrates 11, 11a, 11b as the scintillator 1. In a configuration in which the wiring members 30, 30a, 30b are arranged on the same side of the semiconductor substrates 11, 11a, 11b as the scintillator 1, there is no need to prepare a new substrate for connecting the wiring members 30, 30a, 30b to the first and second electrodes 17, 18 by die bonding, for example. Therefore, this configuration more reliably simplifies the configuration of the radiation detectors RD1, RD2. The flexibility of the wiring members 30, 30a, 30b does not need to be greater than the flexibility of the semiconductor substrates 11, 11a, 11b. If the flexibility of the wiring members 30, 30a, 30b is greater than the flexibility of the semiconductor substrates 11, 11a, 11b, as described above, vibrations are less likely to be transmitted from the wiring members 30, 30a, 30b to the semiconductor substrates 11, 11a, 11b. Therefore, this configuration reliably maintains the mechanical strength of the radiation detectors RD1, RD2. [Explanation of symbols]

[0303] 1...scintillator, 1a...end surface, 1b...end surface, 1c...side surface, 1p...portion, 1q...portion, 1r...portion, 1s...portion, 3a...facing surface, 3b...facing surface, 3c...connecting surface, 3e...connecting surface, 3a...facing surface, 3b...facing surface, 10...semiconductor photodetector element, 10a...first semiconductor photodetector element, 10b...second semiconductor photodetector element, 11...semiconductor substrate, 11a...first semiconductor substrate, 11b...second semiconductor substrate, 12...avalanche photodiode, 13...quenching resistor, 14a...conductor, 14b...conductor, 17a...first electrode, 17b...first electrode, 17c...first electrode, 1 7d...first electrode, 18...second electrode, 21...first portion, 22...second portion, 23...light detection region, 24...light reflecting member, 30...wiring member, 30a...first wiring member, 30b...second wiring member, 41...first terminal, 42...second terminal, 43...first wire, 44...second wire, 45...resin, 47...light reflector, 47a...first light reflector, 47b...second light reflector, 51...third portion, 52...fourth portion, D1...first direction, D2...second direction, D3...third direction, RA1...radiation detector array, RA2...radiation detector array, RD1...radiation detector, RD2...radiation detector.

Claims

1. a scintillator having a pair of end faces facing each other in a first direction and a side face connecting the pair of end faces; a semiconductor light-detecting element having a semiconductor substrate disposed so as to face the side surface; a wiring member electrically connected to the semiconductor light-detecting element; Equipped with a length of the scintillator in the first direction is greater than a length of the scintillator in a second direction perpendicular to the side surface; a length of the side surface in the first direction is greater than a width of the side surface in a third direction perpendicular to the first direction and the second direction; The semiconductor substrate is a first portion covered by the side surface and having a plurality of light detection regions disposed therein; a second portion aligned with the first portion in the first direction and exposed from the side surface, the plurality of photodetection regions are aligned in the first direction, and each of the photodetection regions includes at least one avalanche photodiode operating in a Geiger mode, and at least one quenching resistor electrically connected in series with one of an anode and a cathode of a corresponding one of the at least one avalanche photodiodes; The second portion comprises: a plurality of first electrodes electrically connected to the at least one quenching resistor included in a corresponding one of the plurality of photodetection regions; a second electrode electrically connected to the other of the anode and the cathode of each of the avalanche photodiodes; the wiring member includes a plurality of conductors electrically connected to corresponding first electrodes among the plurality of first electrodes, and a conductor connected to the second electrode; the plurality of light detection regions include a first light detection region and a second light detection region that is closer to the second portion than the first light detection region; a width of a conductor electrically connecting the first electrode corresponding to the first light detection region and the first light detection region is greater than a width of a conductor electrically connecting the first electrode corresponding to the second light detection region and the second light detection region.

2. The radiation detector according to claim 1 , wherein at least one of the pair of end faces is inclined with respect to the second direction.

3. The radiation detector according to claim 1 , wherein the end face extending in the second direction out of the pair of end faces has a cross section that is triangular wave shaped.

4. The radiation detector according to claim 1 , wherein the end surface of the pair of end surfaces that extends in the second direction is a rough surface.

5. 5. The radiation detector according to claim 1, wherein the scintillator has another side surface that connects the pair of end surfaces and is adjacent to the side surface, and that has a triangular wave-shaped cross section.

6. 5. The radiation detector according to claim 1, wherein the scintillator has another side surface that is a rough surface and connects the pair of end surfaces and is adjacent to the side surface.

7. 7. The radiation detector according to claim 1, wherein, when viewed from the second direction, one area formed by the outlines of the plurality of light detection areas has a shape corresponding to the outline shape of the side surface.

8. the scintillator has a plurality of independent portions corresponding to the plurality of photodetection regions, 2. The radiation detector according to claim 1, wherein each of the plurality of portions has a pair of opposing surfaces facing each other in the first direction, and a connecting surface connecting the pair of opposing surfaces and facing the semiconductor substrate.

9. The radiation detector of claim 8 , wherein the portions are bonded together.

10. The radiation detector according to claim 8 , wherein at least one of the pair of opposing surfaces is inclined with respect to the second direction.

11. The radiation detector according to any one of claims 8 to 10, wherein of the pair of opposing surfaces, the opposing surface extending in the second direction has a cross section that is triangular wave shaped.

12. The radiation detector according to any one of claims 8 to 10, wherein the opposing surface extending in the second direction out of the pair of opposing surfaces is a rough surface.

13. The radiation detector according to any one of claims 8 to 12, wherein the scintillator has another connecting surface that connects the pair of opposing surfaces and is adjacent to the connecting surface and has a triangular wave-shaped cross section.

14. 13. The radiation detector according to claim 8, wherein the scintillator has another connecting surface that connects the pair of opposing surfaces and is a rough surface adjacent to the connecting surfaces.

15. 15. The radiation detector according to claim 8, wherein, when viewed from the second direction, each of the plurality of light detection regions has a contour shape that corresponds to a contour shape of the coupling surface, facing the semiconductor substrate, of a corresponding one of the plurality of portions.

16. The radiation detector according to any one of claims 1 to 15, wherein the scintillator has a rectangular or triangular shape when viewed from the first direction.

17. a substrate disposed between the scintillator and the semiconductor substrate; the base body has a third portion covered with the semiconductor substrate and a fourth portion aligned with the third portion in the first direction and exposed from the semiconductor substrate; the fourth portion includes a first terminal and a second terminal that are arranged on the same side of the semiconductor substrate as the scintillator, 17. The radiation detector according to claim 1, wherein the first terminal is electrically connected to the first electrode by a first wire, and the second terminal is electrically connected to the second electrode by a second wire.

18. The radiation detector of claim 17 , wherein the first wire and the second wire are covered with a resin.

19. 19. The radiation detector according to claim 1, further comprising a light reflector arranged such that the semiconductor substrate is located between the light reflector and the scintillator.

20. 20. The radiation detector according to claim 19, wherein the light reflector has a thickness of 0.05 to 100 μm.

21. The radiation detector according to any one of claims 1 to 20, wherein the wiring member is arranged on the same side of the semiconductor substrate as the scintillator.

22. the wiring member and the semiconductor substrate are flexible, The radiation detector according to any one of claims 1 to 21, wherein the wiring member has a flexibility greater than that of the semiconductor substrate.

23. a scintillator having a rectangular shape when viewed from a first direction, and including a pair of end faces facing each other in the first direction, a first side face connecting the pair of end faces, and a second side face connecting the pair of end faces and adjacent to the first side face; a first semiconductor photodetector element having a first semiconductor substrate disposed so as to face the first side surface; a second semiconductor photodetector element having a second semiconductor substrate disposed so as to face the second side surface; a first wiring member electrically connected to the first semiconductor photodetector element; a second wiring member electrically connected to the second semiconductor light-detecting element; Equipped with a length of the scintillator in the first direction is greater than a length of the scintillator in a second direction perpendicular to the first side surface and a length of the scintillator in a third direction perpendicular to the second side surface; a length of the first side surface in the first direction greater than a width of the first side surface in the third direction; a length of the second side in the first direction greater than a width of the second side in the second direction; The first semiconductor substrate and the second semiconductor substrate are a first portion covered by one of the corresponding first side surface and the corresponding second side surface and in which a plurality of light detection regions are arranged; and a second portion aligned with the first portion in the first direction and exposed from the corresponding one of the first side surface and the corresponding second side surface, the plurality of photodetection regions are aligned in the first direction, and each of the photodetection regions includes at least one avalanche photodiode operating in a Geiger mode, and at least one quenching resistor electrically connected in series with one of an anode and a cathode of a corresponding one of the at least one avalanche photodiodes; The second portion comprises: a plurality of first electrodes electrically connected to the at least one quenching resistor included in a corresponding one of the plurality of photodetection regions; a second electrode electrically connected to the other of the anode and the cathode of each of the avalanche photodiodes; the first wiring member and the second wiring member each include a plurality of conductors electrically connected to corresponding first electrodes among the plurality of first electrodes, and a conductor connected to the second electrode; the plurality of light detection regions include a first light detection region and a second light detection region that is closer to the second portion than the first light detection region; a width of a conductor electrically connecting the first electrode corresponding to the first light detection region and the first light detection region is greater than a width of a conductor electrically connecting the first electrode corresponding to the second light detection region and the second light detection region.

24. The radiation detector according to claim 23 , wherein at least one of the pair of end faces is inclined with respect to the second direction.

25. The radiation detector according to claim 23 or 24, wherein the end face extending in the second direction out of the pair of end faces has a triangular wave shape in cross section.

26. The radiation detector according to claim 23 or 24, wherein the end surface of the pair of end surfaces that extends in the second direction is a rough surface.

27. When viewed from the second direction, one region formed by the outlines of the plurality of light detection regions has a shape corresponding to the outline shape of the side surface, The radiation detector according to any one of claims 23 to 26, wherein, when viewed from the third direction, one area formed by the outlines of the plurality of light detection areas has a shape corresponding to the outline shape of the side surface.

28. the scintillator has a plurality of independent portions corresponding to the plurality of photodetection regions, 24. The radiation detector according to claim 23, wherein each of the plurality of portions has a pair of opposing surfaces facing each other in a first direction, a first coupling surface connecting the pair of opposing surfaces and facing the first semiconductor substrate, and a second coupling surface connecting the pair of opposing surfaces, facing the second semiconductor substrate, and adjacent to the first coupling surface.

29. 30. The radiation detector of claim 28, wherein the portions are bonded together.

30. The radiation detector according to claim 28 or 29, wherein at least one of the pair of opposing surfaces is inclined with respect to the second direction.

31. The radiation detector according to any one of claims 28 to 30, wherein of the pair of opposing surfaces, the opposing surface extending in the second direction has a cross section that is triangular wave shaped.

32. The radiation detector according to any one of claims 28 to 30, wherein the opposing surface of the pair of opposing surfaces that extends in the second direction is a rough surface.

33. When viewed from the second direction, each of the plurality of light detection regions has a contour shape that corresponds to a contour shape of the first coupling surface of a corresponding one of the plurality of portions that faces the first semiconductor substrate, and The radiation detector according to any one of claims 28 to 32, wherein, when viewed from the third direction, each of the plurality of light detection regions has a contour shape that corresponds to a contour shape of the second coupling surface, facing the second semiconductor substrate, of a corresponding one of the plurality of portions.

34. a first base disposed so that the first semiconductor substrate is located between the first base and the scintillator; a second substrate disposed so that the second semiconductor substrate is located between the second substrate and the scintillator; Further provided with the first substrate and the second substrate each have a third portion covered with the first semiconductor substrate and the second semiconductor substrate, and a fourth portion aligned with the third portion in the first direction and exposed from the first semiconductor substrate and the second semiconductor substrate, each of the fourth portions includes a first terminal and a second terminal that are arranged on the same side as the scintillator with respect to the corresponding first semiconductor substrate or the corresponding second semiconductor substrate; The radiation detector according to any one of claims 23 to 33, wherein the first terminal is electrically connected to the first electrode by a first wire, and the second terminal is electrically connected to the second electrode by a second wire.

35. 35. The radiation detector of claim 34, wherein the first wire and the second wire are covered with a resin.

36. a first light reflector arranged so that the first semiconductor substrate is located between the first light reflector and the scintillator; The radiation detector according to any one of claims 23 to 35, further comprising: a second optical reflector arranged such that the second semiconductor substrate is located between the second optical reflector and the scintillator.

37. 37. The radiation detector according to claim 36, wherein the first light reflector and the second light reflector have a thickness of 0.05 to 100 μm.

38. the first wiring member is disposed on the same side as the scintillator with respect to the first semiconductor substrate, The radiation detector according to any one of claims 23 to 37, wherein the second wiring member is arranged on the same side as the scintillator with respect to the second semiconductor substrate.

39. the first wiring member, the second wiring member, the first semiconductor substrate, and the second semiconductor substrate are flexible; the flexibility of the first wiring member is greater than the flexibility of the first semiconductor substrate; The radiation detector according to any one of claims 23 to 38, wherein the flexibility of the second wiring member is greater than the flexibility of the second semiconductor substrate.

40. a radiation detector array in which a plurality of radiation detectors are two-dimensionally arranged in a matrix as viewed from a first direction, Each of the plurality of radiation detectors is the radiation detector according to any one of claims 1 to 22, A radiation detector array, wherein the semiconductor photodetector element of one of the radiation detectors is aligned with the semiconductor photodetector element of another of the radiation detectors adjacent to it in a direction parallel to the side surface.

41. 41. The radiation detector array according to claim 40, wherein the semiconductor photodetector elements adjacent to each other in a direction parallel to the side surfaces are integrally formed with each other.

42. a radiation detector array in which a plurality of radiation detectors are two-dimensionally arranged in a matrix as viewed from a first direction, Each of the plurality of radiation detectors is the radiation detector according to any one of claims 23 to 39, the first semiconductor photodetection element of one of the radiation detectors is aligned with the first semiconductor photodetection element of another of the radiation detectors adjacent to it in the third direction, a radiation detector array in which the second semiconductor photodetector element of one of the radiation detectors is aligned with the second semiconductor photodetector element of another of the radiation detectors adjacent to it in the second direction.

43. 43. The radiation detector array of claim 42, wherein each of the first semiconductor photodetector elements adjacent to each other in the third direction are integrally formed with each other.

44. 44. The radiation detector array according to claim 42 or 43, wherein the second semiconductor photodetection elements adjacent to each other in the second direction are integrally formed with each other.

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