Radiation detectors and radiation detector arrays

Abstract

To provide a radiation detector with high temporal resolution.SOLUTION: A radiation detector RD1 comprises: a scintillator 1 that has a pair of end surfaces 1a and 1b opposed to each other in a first direction D1, and a lateral face 1c coupling between the end surfaces 1a and 1b; a semiconductor light detection element 10 that has a semiconductor substrate 11; and a wiring member 30 electrically connected with the semiconductor light detection element 10. A length of the scintillator 1 in the first direction D1 is longer than that in a second direction D2 orthogonal to the lateral face 1c. A length of the lateral face 1c in the first direction D1 is longer than a width of the lateral face 1c in a third direction D3 orthogonal to the first direction D1 and the second direction D2. On the semiconductor substrate 11, a light detection region 23 that has a plurality of avalanche photodiodes 12 operating in a Geiger mode and a plurality of quenching resistors, is arranged.SELECTED DRAWING: Figure 1

Description

Technical Field

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[0001] The present invention relates to a radiation detector and a radiation detector array.

Background Art

[0002] There is known a radiation detector including a scintillator having a hexahedral shape and a semiconductor photodetector having a semiconductor substrate disposed on the scintillator (see, for example, Patent Document 1). The scintillator receives radiation incidence and generates scintillation light, and the generated scintillation light is detected by the semiconductor photodetector.

Prior Art Documents

Patent Documents

[0003]

【Patent Document​​​​​​​​​​​​​​​​​​​​A scintillator that is long in the first direction reliably absorbs high-energy radiation and generates scintillation light when radiation is incident on one of a pair of end faces that face each other in the first direction. In a configuration where a semiconductor photodetector is placed on the other end face of the pair, high-energy radiation is easily absorbed. However, high temporal resolution is difficult to obtain with this configuration. A semiconductor photodetector detects scintillation light that is directly incident on one end face. It also detects scintillation light that is reflected by one end face before being incident on the other end face. These two types of scintillation light are generated simultaneously within the scintillator. However, these two types of scintillation light are detected by the semiconductor photodetector with a large time difference. High temporal resolution detection is difficult to achieve. Therefore, in a radiation detector, it is desirable to position the semiconductor photodetector elements in a location that allows for the detection of each simultaneously generated scintillation light without a large time difference. With this arrangement of semiconductor photodetectors, incident radiation can be detected with high temporal resolution.

[0006] A radiation detector according to the first embodiment comprises a scintillator having a pair of end faces facing each other in a first direction and a side surface connecting the pair of end faces; a semiconductor photodetector having a semiconductor substrate arranged to face the side surface; and a wiring member electrically connected to the semiconductor photodetector. 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 surface. The length of the side surface in the first direction is greater than the width of the side surface in a third direction perpendicular to the first and second directions. The semiconductor substrate has a first portion covered by the side surface and a second portion aligned with the first portion in the first direction and exposed from the side surface. The first portion has a photodetector region having a plurality of avalanche photodiodes operating in Geiger mode and a plurality of quenching resistors electrically connected in series with one of the anodes and cathodes of the corresponding avalanche photodiodes. The second portion has a first electrode to which a plurality of quenching resistors are connected in parallel and a second electrode to which the other of the anodes and cathodes of the plurality of avalanche photodiodes are connected in parallel. The wiring component has a conductor electrically connected to the first electrode and a conductor connected to the second electrode.

[0007] According to the first embodiment described above, the radiation detector includes a scintillator that is long in the first direction, and a semiconductor photodetector positioned on the side of the scintillator. The semiconductor photodetector not only detects scintillation light that is directly incident on the side on which the semiconductor photodetector is positioned, but also detects scintillation light that is incident on the side after being reflected by another side opposite to the side on which the semiconductor photodetector is positioned. Since the length of the scintillator in the second direction is smaller than the length of the scintillator in the first direction, the scintillation light that is directly incident on the side and the scintillation light that is incident on the side after being reflected by another side are detected by the semiconductor photodetector with a small time difference. Therefore, the first embodiment described above achieves high temporal resolution.

[0008] In the first embodiment described above, the scintillator may be rectangular or triangular in shape when viewed from the first direction. In configurations where the scintillator is rectangular or triangular in shape, scintillation light is reliably incident on the side facing the semiconductor substrate. Therefore, this configuration reliably improves the amount of light received by the semiconductor photodetector.

[0009] In the first embodiment described above, at least one of the pair of end faces may be inclined with respect to the second direction. In a configuration where at least one end face is inclined with respect to the second direction, scintillation light is more reliably incident on the side facing the semiconductor substrate. Since the number of times scintillation light is reflected by the end face or side face is reduced, and the reflection attenuation is also reduced, this configuration more reliably improves the amount of light received by the semiconductor photodetector.

[0010] In the first embodiment described above, of the pair of end faces, the end face extending in the second direction may have a cross-section that exhibits a triangular wave shape. In a configuration where the cross-section of the end face extending in the second direction exhibits a triangular wave shape, scintillation light is more reliably incident on the side surface facing the semiconductor substrate. Since the number of times the scintillation light is reflected by the end face or side surface is reduced, and the reflection attenuation is also reduced, this configuration more reliably improves the amount of light received by the semiconductor photodetector.

[0011] In one of the above embodiments, the end face of the pair that extends in the second direction may be a rough surface. In a configuration where the end face extending in the second direction is rough, scintillation light is more reliably incident on the side surface facing the semiconductor substrate. Since the number of times scintillation light is reflected by the end face or side surface is reduced, and the reflection attenuation is also reduced, this configuration more reliably improves the amount of light received by the semiconductor photodetector.

[0012] In the first embodiment described above, the scintillator may have another side surface adjacent to the side surface, which has a triangular wave cross-section and connects a pair of end faces. In a configuration where the cross-section of another side is triangular wave-shaped, scintillation light is more reliably incident on the side facing the semiconductor substrate. Therefore, this configuration more reliably improves the amount of light received by the semiconductor photodetector.

[0013] In the first embodiment described above, the scintillator may have another rough surface that connects a pair of end faces and is adjacent to the side face. In a configuration where another side is rough, scintillation light is more reliably incident on the side facing the semiconductor substrate. Therefore, this configuration more reliably improves the amount of light received by the semiconductor photodetector.

[0014] In the first embodiment described above, when viewed from the second direction, the light detection region may have a contour shape corresponding to the contour shape of the side surface. In a configuration where the photodetector region exhibits a contour shape corresponding to the side contour, it is not necessary to place the photodetector region in areas of the semiconductor substrate that cannot receive scintillation light. Therefore, the increase in dark count and capacitance in the photodetector region is suppressed. Consequently, this configuration reliably improves the temporal resolution of the radiation detector.

[0015] In the first embodiment described above, the substrate may further include a substrate positioned such that a semiconductor substrate is located between it and the scintillator. The substrate may have a third portion covered by 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 located on the same side as the scintillator with respect to the semiconductor substrate. The first terminal may be electrically connected by a first electrode and a first wire, and the second terminal may be electrically connected by a second electrode and a second wire. In a configuration that includes a substrate, the mechanical strength of the radiation detector is reinforced. Therefore, this configuration reliably realizes a radiation detector with reinforced mechanical strength.

[0016] In the first embodiment described above, the first wire and the second wire may be covered with resin. In a configuration where the first wire and the second wire are covered with resin, the resin protects the first and second wires, so it is difficult for the first and second wires to be damaged. Therefore, this configuration suppresses deterioration of the electrical connection between the first and second terminals and the first and second electrodes.

[0017] In the above first aspect, a light reflector may be further provided which is arranged such that a semiconductor substrate is located between the light reflector and the scintillator. In a configuration provided with a light reflector, when one radiation detector is arranged side by side with another radiation detector in the second direction, the light reflector of one radiation detector improves the reflectance of scintillation light on the other side surface facing the side surface of the other radiation detector in the second direction. The other side surface of the other radiation detector has a high reflectance with respect to scintillation light even in a configuration where no light reflector is arranged. Therefore, this configuration simplifies the configuration of the radiation detector.

[0018] In the above first aspect, the thickness of the light reflector may be 0.05 to 100 μm. In a configuration where the thickness of the light reflector is within the above range, the reflectance of scintillation light on the other side surface is surely improved. Therefore, this configuration surely simplifies the configuration of the radiation detector.

[0019] In the above first aspect, the wiring member may be arranged on the same side of the semiconductor substrate as the scintillator. In a configuration where the wiring member is arranged on the same side of the semiconductor substrate as the scintillator, for example, there is no need to newly prepare a substrate for connecting the wiring member to the first and second electrodes by die bonding. Therefore, this configuration more surely simplifies the configuration of the radiation detector.

[0020] In the above first aspect, the wiring member and the semiconductor substrate may have flexibility. The flexibility of the wiring member may be greater than the flexibility of the semiconductor substrate. In a configuration where the flexibility of the wiring component is greater than that of the semiconductor substrate, vibrations are less likely to be transmitted from the wiring component to the semiconductor substrate. Less force is applied to the semiconductor substrate from the wiring component, making the semiconductor substrate less susceptible to physical damage. Therefore, this configuration reliably maintains the mechanical strength of the radiation detector.

[0021] A radiation detector according to a second embodiment comprises a scintillator having a rectangular shape when viewed from a first direction and having a pair of end faces facing each other in the first direction, a first side surface connecting the pair of end faces, and a second side surface connecting the pair of end faces and adjacent to the first side surface; a first semiconductor photodetector having a first semiconductor substrate arranged to face the first side surface; a second semiconductor photodetector having a second semiconductor substrate arranged to face the second side surface; a first wiring member electrically connected to the first semiconductor photodetector; and a second wiring member electrically connected to the second semiconductor photodetector. The length of the scintillator in the first direction is greater than the length of the scintillator in the second direction perpendicular to the first side surface and the length of the scintillator in the third direction perpendicular to the second side surface. The length of the first side surface in the first direction is greater than the width of the first side surface in the third direction, and the length of the second side surface in the first direction is greater than the width of the second side surface in the second direction. The first and second semiconductor substrates each have a first portion covered by either the corresponding first or second side, and a second portion aligned with the first portion in the first direction and exposed from either the corresponding first or second side. The first portion has a photodetection region having a plurality of avalanche photodiodes operating in Geiger mode and a plurality of quenching resistors electrically connected in series with one of the anodes and cathodes of the avalanche photodiodes. The second portion has a first electrode to which a plurality of quenching resistors are connected in parallel, and a second electrode to which the other of the anodes and cathodes of the plurality of avalanche photodiodes are connected in parallel. The first and second wiring members each have a conductor electrically connected to the first electrode and a conductor connected to the second electrode.

[0022] According to the second aspect, the radiation detector includes a scintillator that is long in the first direction and a semiconductor light detection element disposed on a side surface of the scintillator. The semiconductor light detection element not only detects scintillation light that directly enters the side surface on which the semiconductor light detection element is disposed, but also detects, for example, scintillation light that enters the side surface after being reflected by another side surface facing the side surface on which the semiconductor light detection element is disposed. Since the length of the scintillator in the second direction is smaller than the length of the scintillator in the first direction, the scintillation light that directly enters the side surface and the scintillation light that enters the side surface after reflection on another side surface are detected by the semiconductor light detection element with a small time difference. Therefore, the second aspect realizes high time resolution. According to the second aspect, even when the incident angle of the scintillation light on the first side surface exceeds the critical angle on the first side surface and is not detected by the first semiconductor light detection element disposed on the first side surface, the scintillation light is detected by the second semiconductor light detection element disposed on the second side surface adjacent to the first side surface. Therefore, the second aspect realizes a radiation detector having high time resolution and surely improves the light reception amounts of the first and second semiconductor light detection elements for the scintillation light.

[0023] In the second aspect, at least one of the pair of end faces may be inclined with respect to the second direction. In the configuration in which at least one of the end faces is inclined with respect to the second direction, the scintillation light more surely enters the side surface facing the first and second semiconductor substrates. Since the number of times the scintillation light is reflected by the end face or the side surface is reduced and the reflection attenuation is also reduced, this configuration more surely improves the light reception amounts of the first and second semiconductor light detection elements.

[0024] In the second aspect, among the pair of end faces, the end face extending in the second direction may have a triangular wave shape in cross section. In a configuration where the cross-section of the end face extending in the second direction exhibits a triangular wave shape, scintillation light is more reliably incident on the side surface facing the first and second semiconductor substrates. Since the number of times the scintillation light is reflected by the end face or side surface is reduced, and the reflection attenuation is also reduced, this configuration more reliably improves the amount of light received by the first and second semiconductor photodetectors.

[0025] In the second embodiment described above, at least one of the pair of end faces may be a rough surface. In a configuration where the end face extending in the second direction is rough, scintillation light is more reliably incident on the side surface facing the first and second semiconductor substrates. Since the number of times scintillation light is reflected by the end face or side surface is reduced, and the reflection attenuation is also reduced, this configuration more reliably improves the amount of light received by the first and second semiconductor photodetectors.

[0026] In the second embodiment described above, when viewed from a second direction, the photodetector region of the first semiconductor substrate may have a contour shape corresponding to the contour shape of the first side surface. When viewed from a third direction, the photodetector region of the second semiconductor substrate may have a contour shape corresponding to the contour shape of the second side surface. In a configuration where the photodetector region has a contour shape corresponding to the contour shapes of the first and second sides, it is not necessary to place the photodetector region in areas of the first and second semiconductor substrates that cannot receive scintillation light, respectively. Therefore, the increase in dark count and capacitance in the photodetector region is suppressed. Consequently, this configuration reliably improves the time resolution of the first and second semiconductor photodetector elements.

[0027] In the second embodiment described above, the apparatus may further include a first substrate positioned such that a first semiconductor substrate is located between it and a scintillator, and a second substrate positioned such that a second semiconductor substrate is located between it and a scintillator. The first substrate and the second substrate may each have a third portion covered by the first and second semiconductor substrates, and a fourth portion aligned with the third portion in the first direction and exposed from the first and second semiconductor substrates. Each fourth portion may include a first terminal and a second terminal located on the same side as the scintillator with respect to the corresponding first or second semiconductor substrate. The first terminal may be electrically connected by a first electrode and a first wire, and the second terminal may be electrically connected by a second electrode and a second wire. In configurations comprising a first and a second substrate, the mechanical strength of the radiation detector is reinforced in each case. Therefore, this configuration reliably realizes a radiation detector with reinforced mechanical strength.

[0028] In the second embodiment described above, the first wire and the second wire may be covered with resin. In a configuration where the first and second wires are covered with resin, the resin protects the first and second wires, making them less susceptible to damage. Therefore, this configuration suppresses deterioration of the electrical connection between the first and second terminals and the first and second electrodes.

[0029] In the second embodiment described above, the system may further include a first light reflector positioned between itself and a scintillator, and a second light reflector positioned between itself and a scintillator, and a second semiconductor substrate positioned between itself and a scintillator. In a configuration comprising a first and a second light reflector, the first light reflector improves the reflectivity of scintillation light on the second side surface of adjacent radiation detectors in the second direction. The other sides of radiation detectors have high reflectivity to scintillation light even in configurations without the first light reflector. The second light reflector improves the reflectivity of scintillation light on the side surface of adjacent radiation detectors in the third direction. The other sides of radiation detectors have high reflectivity to scintillation light even in configurations without the second light reflector. Therefore, this configuration reliably simplifies the configuration of the radiation detectors.

[0030] In the second embodiment described above, the thickness of the first light reflector and the second light reflector may be 0.05 to 100 μm. In configurations where the thicknesses of the first and second light reflectors are within the above range, the reflectivity of scintillation light on the other sides is reliably improved. Therefore, this configuration reliably simplifies the configuration of the radiation detector.

[0031] In the second embodiment described above, the first wiring member may be positioned on the same side as the scintillator with respect to the first semiconductor substrate. The second wiring member may be positioned on the same side as the scintillator with respect to the second semiconductor substrate. In a configuration where the first and second wiring members are positioned on the same side as the scintillator with respect to the first and second semiconductor substrates, respectively, it is not necessary to prepare new substrates for connecting the first and second wiring members to the first and second electrodes, for example, by die bonding. Therefore, this configuration more reliably simplifies the structure of the radiation detector.

[0032] In the second embodiment described above, the first wiring member and the second wiring member, and 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 where the flexibility of the first and second wiring members is greater than that of the first and second semiconductor substrates, 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, making them less susceptible to physical damage. Therefore, this configuration reliably maintains the mechanical strength of the radiation detector.

[0033] The radiation detector array according to the third embodiment is a radiation detector array in which, when viewed from a first direction, a plurality of radiation detectors are arranged in a matrix in a two-dimensional manner, each of the plurality of radiation detectors being a radiation detector according to the first embodiment, and the semiconductor photodetector element of one radiation detector is aligned with the semiconductor photodetector element of another radiation detector that is adjacent to it in a direction parallel to the side surface.

[0034] According to the third embodiment described above, a radiation detector array is realized in which radiation detectors having high temporal resolution are arranged in a matrix in a two-dimensional manner.

[0035] In the third embodiment described above, each semiconductor photodetector adjacent to each other in a direction parallel to the side surface may be formed integrally with one another. In a configuration where each semiconductor photodetector is integrally formed with the others, the process of forming the semiconductor photodetectors is simplified when fabricating a radiation detector array in which multiple radiation detectors are arranged in a two-dimensional matrix.

[0036] The radiation detector array according to the fourth embodiment is a radiation detector array in which, when viewed from the first direction, a plurality of radiation detectors are arranged in a matrix in a two-dimensional manner, each of the plurality of radiation detectors being a radiation detector according to the second embodiment, the first semiconductor photodetector of one radiation detector is aligned with the first semiconductor photodetector of another radiation detector adjacent in the third direction, and the second semiconductor photodetector of one radiation detector is aligned with the second semiconductor photodetector of yet another radiation detector adjacent in the second direction.

[0037] According to the fourth embodiment described above, a radiation detector array is realized in which radiation detectors having high temporal resolution are arranged in a matrix in a two-dimensional manner.

[0038] In the fourth embodiment described above, each first semiconductor photodetector adjacent to one another in the third direction may be formed integrally with one another. In a configuration where each first semiconductor photodetector is integrally formed with respect to the others, the process of forming the first semiconductor photodetector is simplified when fabricating a radiation detector array in which multiple radiation detectors are arranged in a matrix in a two-dimensional manner.

[0039] In the fourth embodiment described above, each second semiconductor photodetector adjacent to one another in the second direction may be formed integrally with one another. In a configuration where each second semiconductor photodetector is integrally formed with respect to the others, the process of forming the second semiconductor photodetector is simplified when fabricating a radiation detector array in which multiple radiation detectors are arranged in a two-dimensional matrix. [Effects of the Invention]

[0040] First and second aspects of the present invention provide radiation detectors having high temporal resolution. Third and fourth aspects of the present invention provide radiation detector arrays equipped with radiation detectors having high temporal resolution. [Brief explanation of the drawing]

[0041] [Figure 1] Figure 1 is a perspective view showing a radiation detector according to the first embodiment. [Figure 2] Figure 2 is a plan view showing a semiconductor photodetector. [Figure 3] Figure 3 shows the equivalent circuit of the photodetector region. [Figure 4] Figure 4 is a perspective view showing a radiation detector according to the first embodiment. [Figure 5] Figure 5 shows some of the paths of scintillation light. [Figure 6] Figure 6 shows some of the paths of scintillation light. [Figure 7] Figure 7 shows some of the paths of scintillation light. [Figure 8] Figure 8 shows an example of the contour shape of another side. [Figure 9] Figure 9 is a perspective view showing a radiation detector according to a first modified example of the first embodiment. [Figure 10] Figure 10 shows some of the paths of scintillation light. [Figure 11] Figure 11 is a perspective view showing a radiation detector according to a second modified example of the first embodiment. [Figure 12] Figure 12 is a perspective view showing a radiation detector according to a third modified example of the first embodiment. [Figure 13] Figure 13 shows some of the paths of scintillation light. [Figure 14] Figure 14 is a perspective view showing a radiation detector according to a fourth modification of the first embodiment. [Figure 15] Figure 15 shows some of the paths of scintillation light. [Figure 16] Figure 16 is a perspective view showing a radiation detector according to a fifth modified example of the first embodiment. [Figure 17] Figure 17 is a plan view showing a semiconductor photodetector. [Figure 18] Figure 18 is a perspective view showing a radiation detector according to the sixth modified example of the first embodiment. [Figure 19] Figure 19 is a plan view showing a semiconductor photodetector. [Figure 20] Figure 20 is a perspective view showing a radiation detector according to the seventh modified example of the first embodiment. [Figure 21] Figure 21 is a plan view showing a semiconductor photodetector. [Figure 22] Figure 22 is a perspective view showing a radiation detector according to the second embodiment. [Figure 23] Figure 23 shows some of the paths of scintillation light. [Figure 24]Figure 24 is a perspective view showing a radiation detector according to the first modified example of the second embodiment. [Figure 25] Figure 25 is a perspective view showing a radiation detector according to a second modified example of the second embodiment. [Figure 26] Figure 26 is a perspective view showing a radiation detector according to a third modified example of the second embodiment. [Figure 27] Figure 27 is a perspective view showing a radiation detector array according to the third embodiment. [Figure 28] Figure 28 is a perspective view showing a radiation detector array according to the fourth embodiment. [Modes for carrying out the invention]

[0042] Embodiments of the present invention will be described in detail with reference to the attached drawings. In this description, the same reference numerals will be used for elements that are the same or have the same function, and redundant descriptions will be omitted.

[0043] (First Embodiment) The configuration of the radiation detector RD1 according to the first embodiment will be described with reference to Figures 1 to 4. Figure 1 is a perspective view showing the radiation detector according to the first embodiment. Figure 2 is a plan view showing the semiconductor photodetector. Figure 3 is a diagram showing the equivalent circuit of the photodetector region. Figure 4 is a perspective view showing the radiation detector according to the first embodiment.

[0044] As shown in Figure 1, the radiation detector RD1 comprises a scintillator 1, a semiconductor photodetector 10, and a wiring member 30. The scintillator 1 generates scintillation light (fluorescence) upon incident radiation. The semiconductor photodetector 10 detects the scintillation light generated by the scintillator 1. The semiconductor photodetector 10 has a semiconductor substrate 11 and is electrically connected to the wiring member 30.

[0045] The scintillator 1 has a pair of opposing end faces 1a, 1b, a pair of opposing side faces 1c, 1d, and a pair of opposing side faces 1e, 1f. The end faces 1a, 1b, the side faces 1c, 1d, and the side faces 1e, 1f constitute the outer surface of the scintillator 1. The end faces 1a, 1b are opposite each other in the first direction D1. The end faces 1a, 1b define both ends of the scintillator 1 in the first direction D1. The side faces 1c, 1d are opposite each other in the second direction D2 which intersects the first direction D1. In this embodiment, the second direction D2 coincides with the direction perpendicular to side face 1c. The side faces 1c, 1d define both ends of the scintillator 1 in the second direction D2. The side faces 1e, 1f are opposite each other in the third direction D3 which intersects 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 the ends of scintillator 1 in the third direction D3. The length of scintillator 1 in the first direction D1 is greater than the length of scintillator 1 in the second direction D2, which is perpendicular to side 1c. The first direction D1 is the longitudinal direction of scintillator 1.

[0046] End faces 1a and 1b extend in the second direction D2 to connect side faces 1c and 1d. End faces 1a and 1b extend in the third direction D3 to connect side faces 1e and 1f. Side faces 1c and 1d extend in the first direction D1 to connect end faces 1a and 1b. Side faces 1c and 1d extend in the third direction D3 to connect side faces 1e and 1f. Side faces 1e and 1f extend in the first direction D1 to connect end faces 1a and 1b. Side faces 1e and 1f extend in the second direction D2 to connect side faces 1c and 1d. Side faces 1e and 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.

[0047] The length of scintillator 1 in the first direction D1 is, for example, approximately 20 mm. The length of scintillator 1 in the second direction D2 is, for example, approximately 4 mm. The length of scintillator 1 in the third direction D3 is, for example, approximately 4 mm.

[0048] In this embodiment, the end faces 1a, 1b, the side faces 1c, 1d, and the side faces 1e, 1f are rectangular when viewed from a direction perpendicular to these faces. The scintillator 1 is rectangular when viewed from the second direction D2 and the third direction D3. The scintillator 1 is also rectangular when viewed from the first direction D1. In this embodiment, the scintillator 1 is rectangular in shape. In this specification, "rectangular" includes, for example, shapes where each corner is chamfered and shapes where each corner is rounded. In this specification, "rectangular" includes the shape of a rectangular parallelepiped where the corners and edges are chamfered and shapes where the corners and edges are rounded.

[0049] 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).

[0050] As shown in Figures 1 and 2, the semiconductor substrate 11 is positioned facing the side surface 1c. The semiconductor substrate 11 is disposed on the side surface 1c, for example, via an adhesive. The semiconductor substrate 11 contains, 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 a first direction D1 and is exposed from the side surface 1c.

[0051] As shown in Figures 2 and 3, a photodetection region 23 is arranged in the first part 21. The photodetection region 23 has a plurality of avalanche photodiodes 12 and a plurality of quenching resistors 13. The avalanche photodiodes 12 that receive scintillation light generate photoelectrons by photoelectric conversion. Conductors 14a and 14b are arranged in the first part 21, and the conductor 14a constitutes a wiring pattern for signal reading that is patterned in a grid shape when viewed from a second direction D2, for example. Each grid of the conductor 14a surrounds one photodetection unit 15. One photodetection unit 15 consists of one avalanche photodiode 12 and one quenching resistor 13 that is electrically connected in series with the corresponding avalanche photodiode 12. A plurality of photodetection units 15 are arranged in the first part 21, and the photodetection units 15 are arranged in a two-dimensional matrix, for example. The photodetection region 23 may include one avalanche photodiode 12 and one quenching resistor 13.

[0052] Multiple quenching resistors 13 are electrically connected in series with one of the anodes and cathodes of the corresponding avalanche photodiodes 12. Each avalanche photodiode 12 has a contact electrode 16 that is electrically connected to one of its anodes and cathodes, and one end of the quenching resistor 13 is electrically connected in series with the contact electrode 16. The other end of the quenching resistor 13 is electrically connected in series with a conductor 14a that forms part of the wiring pattern. The conductor 14b electrically connects the other anodes and cathodes of the multiple avalanche photodiodes 12 in parallel.

[0053] The electrical resistivity of the quenching resistor 13 is greater than the electrical resistivity of the first electrode 17 and the second electrode 18. The quenching resistor 13 contains, for example, polysilicon. The material of the quenching resistor 13 may contain, for example, SiCr, NiCr, or FeCr. The quenching resistor 13 is formed, for example, by CVD (Chemical Vapor Deposition) or sputtering.

[0054] The second part 22 contains a first electrode 17 and a second electrode 18. Multiple quenching resistors 13 are connected in parallel to the first electrode 17 via a wire 14a. The other ends of the anodes and cathodes of multiple avalanche photodiodes 12 are connected in parallel to the second electrode 18 via a wire 14b. The first electrode 17 and the second electrode 18 include, for example, aluminum or an aluminum composite (AlSi, AlCu, AlSiCu, etc.). The first electrode 17 and the second electrode 18 are formed, for example, by plating, vapor deposition, or sputtering.

[0055] In this embodiment, the multiple quenching resistors 13 are electrically connected in series with the corresponding avalanche photodiodes 12 among the multiple avalanche photodiodes 12. In this case, the cathodes of the multiple avalanche photodiodes 12 are electrically connected in parallel to the second electrode 18. Alternatively, the multiple quenching resistors 13 may be electrically connected in series with the corresponding avalanche photodiodes 12 among the multiple avalanche photodiodes 12. In this case, the anodes of the multiple avalanche photodiodes 12 are electrically connected in parallel to the second electrode 18.

[0056] 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 to potential V1 is applied to the cathode of the avalanche photodiode 12. The polarity of these potentials is relative, and for example, one of the potentials may be the ground potential. Each photodetector 15 is connected in parallel.

[0057] 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 also include 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.

[0058] The semiconductor substrate 11 includes, for example, a conductor 14a and a conductor 14b, a first electrode 17 connected to the conductor 14a, and a second electrode 18 connected to the conductor 14b. The semiconductor substrate 11 also includes, for example, an insulating layer 19 on the conductors 14a and 14b. The insulating layer 19 extends through a first portion 21 and a second portion 22. In the second portion 22, the first electrode 17 and the conductor 14a are insulated from the second electrode 18 and the conductor 14b by the insulating layer 19. In the first portion 21, the insulating layer 19 is formed on a plurality of photodetectors 15. The insulating layer 19 contains, for example, SiO2 or SiN. The insulating layer 19 is formed, for example, by thermal oxidation, sputtering, or CVD.

[0059] The wiring member 30 is positioned on the same side as the scintillator 1 with respect to the semiconductor substrate 11. The wiring member 30 has a conductor 31 and a conductor 32. Conductor 31 is electrically connected to the first electrode 17, and conductor 32 is electrically connected to the second electrode 18. Conductor 31 is electrically connected to the first electrode 17 via conductive bumps 33. Conductor 32 is connected to the second electrode 18 via conductive bumps 33. Conductive bumps 33 include, for example, solder, ACF (anisotropic conductive film), or ACP (anisotropic conductive paste). The solder includes, for example, Sn-Ag-Cu solder. Conductive bumps 33a may include, for example, Au bumps, Ni bumps, or Cu bumps.

[0060] In this embodiment, a potential V1 is applied to the anode of the avalanche photodiode 12 via conductor 31, and a potential V2 is applied to the cathode of the avalanche photodiode 12 via conductor 32. Alternatively, a potential V1 may be applied to the cathode of the avalanche photodiode 12 via conductor 32, and a potential V2 may be applied to the anode of the avalanche photodiode 12 via conductor 31. Conductors 31 and conductor 32 include, for example, Al, Cu, Cu / Ni / Au, and Cu / Ni / Pd / Au. Conductors 31 and conductor 32 are formed, for example, by sputtering or plating. The wiring member 30 and the photodetection region 23 are flexible, and the flexibility of the wiring member 30 is greater than the flexibility of the photodetection region 23.

[0061] Viewed from the second direction D2, the contour of the photodetection region 23 follows the contour of the side surface 1c. That is, the multiple edges constituting the contour of the photodetection region 23 follow the corresponding edges among the multiple edges constituting the contour of the side surface 1c, as viewed from the second direction D2. Viewed from the second direction D2, the photodetection region 23 exhibits a contour shape corresponding to the contour shape of the side surface 1c. Each photodetection unit 15 is arranged such that, as viewed from the second direction D2, the photodetection region 23 exhibits a contour shape corresponding to the contour shape of the side surface 1c. In this embodiment, as viewed from the second direction D2, the contour shape of the side surface 1c is rectangular, and the photodetection region 23 exhibits a rectangular contour shape corresponding to the contour shape of the side surface 1c. As will be described later, the contour shape of the side surface 1c can be, for example, trapezoidal and parallelogram, in addition to rectangular. When the contour shape of the side surface 1c is trapezoidal, as viewed from the second direction D2, the photodetection region 23 exhibits a trapezoidal contour shape corresponding to the contour shape of the side surface 1c. When viewed from the second direction D2, if the contour shape of the side surface 1c is a parallelogram, the photodetection region 23 will exhibit a parallelogram contour shape corresponding to the contour shape of the side surface 1c.

[0062] The radiation detector RD1 includes, for example, a substrate 40. The substrate 40 is positioned such that a semiconductor substrate 11 is located between the substrate 40 and the scintillator 1. The substrate 40 has a third portion 51 and a fourth portion 52. The third portion 51 is covered by the semiconductor substrate 11. The fourth portion 52 is aligned with the third portion 51 in a first direction D1 and is exposed from the semiconductor substrate 11.

[0063] The fourth part 52 includes a first terminal 41 and a second terminal 42. The first terminal 41 and the second terminal 42 are located on the same side as the semiconductor substrate 11, for example, as the scintillator 1. The first terminal 41 is electrically connected by a first electrode 17 and a first wire 43, and the second terminal 42 is electrically connected by a second electrode 18 and a second wire 44.

[0064] The radiation detector RD1 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 resin 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 point between the first terminal 41 and the first wire 43, and the connection point between the first electrode 17 and the first wire 43. Furthermore, "the resin 45 covers the second wire 44" also includes covering the connection point between the second terminal 42 and the second wire 44, and the connection point between the second electrode 18 and the second wire 44. The wiring member 30 is electrically connected to the first electrode 17 and the second electrode 18 via conductive bumps 46.

[0065] The radiation detector RD1 includes a light reflector 47. The light reflector 47 is positioned 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 positioned such that, for example, 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, semiconductor substrate 11, base 40, and 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, semiconductor substrate 11, and light reflector 47 are arranged in this order.

[0066] The light reflector 47 contains, for example, a metal. The metals contained in the light reflector 47 include, for example, Al, Ag, and Au. The light reflector 47 may also contain a multilayer optical film or Teflon®. The light reflector 47 is formed, for example, by plating, vapor deposition, or sputtering. The thickness of the light reflector 47 is, for example, 0.05 to 100 μm. The radiation detector RD1 does not need to include the light reflector 47.

[0067] Referring to Figures 5 to 8, the paths of scintillation light and the configuration for generating these paths will be described. Figure 5 is a diagram showing a portion of the scintillation light paths. In Figure 5, a portion of the scintillation light paths are shown when the scintillator 1 is viewed from a third direction D3. As described above, scintillation light is generated by the incidence of radiation onto the scintillator 1. The radiation is incident on the scintillator 1 from the end face 1a in the first direction D1, for example. The semiconductor photodetector 10 is positioned facing 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 used to bond the semiconductor photodetector 10 to the scintillator 1 is, for example, 1.5. Therefore, the critical angle of the scintillation light at side face 1c is approximately 56.4 degrees. The illustrated radiation detector RD1 is equipped with light reflectors 47 on the end faces 1a, 1b and the side faces 1d, 1e, 1f. Scintillation light incident on the end faces 1a, 1b and side faces 1d, 1e, 1f is totally reflected by the light reflector 47.

[0068] Scintillation light, for example, is generated within scintillator 1 and then travels in all directions, for example, 360 degrees, from the point of origin GP1. Therefore, the scintillation light includes, for example, light L1 and L2 that are incident directly on side surface 1c from the point of origin GP1. The range of incident angles in which light L1 and L2 can be transmitted to side surface 1c is, for example, 0 to approximately 56.4 degrees. In the example shown in Figure 5, light L1 is incident on side surface 1c at an incident angle of 0 degrees, which is the lower limit of the incident angle. Light L2 is incident on side surface 1c at an incident angle EA1, which is less than the upper limit of the incident angle, 56.4 degrees. Light L2 is not totally reflected at side surface 1c and is transmitted through side surface 1c as long as it is within the region RG1 shown on side surface 1c. Region RG1 shows the maximum region in which light L2 is transmitted through side surface 1c, as viewed from a third direction D3. Light L2 can also enter side surface 1c via the path shown by the dashed line in Figure 5. Light L2 that has passed through side surface 1c is detected by the semiconductor photodetector 10 located on side surface 1c.

[0069] The scintillation light includes, for example, light L3 that initially enters the side surface 1d at an incident angle EA2, in addition to light L1 and L2. Light L3 is totally internalized by side surface 1d. After being totally internalized by side surface 1d, light L3 enters the end surface 1b at an incident angle EA3. After being totally internalized by end surface 1b, light L3 enters the side surface 1c. In the example shown in Figure 5, the incident angle EA4 of light L3 to side surface 1c is smaller than the critical angle at side surface 1c. Light L3 is not totally internalized at side surface 1c and is transmitted through side surface 1c.

[0070] Figure 6 shows a partial path of scintillation light. In Figure 6, a partial path of scintillation light is shown when the scintillator 1 is viewed from the first direction D1. Figure 6 shows that the path of scintillation light from the generation point GP1 to side 1c differs depending on the state of the sides 1e and 1f of the scintillator 1. The semiconductor photodetector 10 is positioned facing side 1c.

[0071] In the scintillator 1 used as an example in Figure 6, two surfaces, 1e and 1f, are roughened. Two surfaces, 1c and 1d, are mirror-finished. The scintillation light includes, in addition to light L1, light L4 incident on side 1d from the generation point GP1 at an incident angle EA5. Light L4 incident on side 1d is totally reflected by side 1d, for example. After being totally reflected by side 1d, light L4 is incident on side 1e, for example at an incident angle EA6. Since side 1e is roughened, light L4 incident on side 1e is directed towards side 1c due to diffuse reflection at side 1e, for example. The diffusely reflected light L4 can then be incident on side 1c. If the incident angle EA7 of light L4 on side 1c is smaller than the critical angle at side 1c, light L4 incident on side 1c is detected by the semiconductor photodetector 10 located on side 1c. 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 at side surface 1c. Since side surface 1f is roughened, it can reflect light L4 toward side surface 1c. If the incident angle EA7 is greater than the critical angle at side surface 1c, the light L4, after being reflected at side surface 1c, may, for example, pass through side surface 1d and then be incident again at side surface 1e. The light L4 that is incident again at side surface 1e may be reflected at side surface 1e so as to be incident at side surface 1c at an incident angle smaller than the critical angle at side surface 1c. Since side surface 1e is rough-finished, the light L4 incident at side surface 1e may exhibit different reflection angles for each reflection, even if the incident angles EA6 are nearly the same. The light L4 incident at side surface 1c at an incident angle smaller than the critical angle at side surface 1c is detected by the semiconductor photodetector 10. If side surface 1e is mirror-finished, it is difficult for the light L4 reflected at side surface 1e to exhibit different reflection angles for each reflection, even if the incident angles EA6 are nearly the same.

[0072] For comparison, Figure 6 shows the path of light L5 incident on side 1e after total internal reflection at side 1d, assuming that sides 1e and 1f are mirror-finished, with a dashed line. Light L5 incident on side 1e at an incident angle EA6 is, for example, totally internally reflected at side 1e. Light L5 that has been totally internally reflected at side 1e may then be incident on side 1f at an incident angle EA6. Light L5 that has been incident on side 1f is, for example, totally internally reflected at side 1f. Light L5 that has been totally internally reflected at side 1f may then be incident on side 1c at an incident angle EA6a. If the incident angle EA6a is smaller than the critical angle at side 1c, light L5 is detected by the semiconductor photodetector 10. Even in this case, the path of light L5 from its source GP1 to side 1c is larger than the path of light L4 from its source GP1 to side 1c. Light L4 is detected by the semiconductor photodetector 10 with a smaller time difference than light L5 compared to light L1. The number of times light L4 is reflected from the side is less than the number of times light L5 is reflected from the side. In the example in Figure 6, for example, if the incident angle EA6 is 30 degrees, then the incident angle EA6a is 60 degrees. The incident angle EA6a is greater than the critical angle at side surface 1c (approximately 56.4 degrees). 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 at side surfaces 1d, 1e, and 1f, respectively. Even when light L5 is incident at side surface 1c and detected by the semiconductor photodetector 10, it undergoes greater reflection attenuation compared to light L4, for example, due to reflection at side surfaces 1d, 1e, and 1f.

[0073] As shown in Figure 6, the scintillation light also includes, for example, light L6 incident on side surface 1f from the point of origin GP1. Side surface 1f is rough-finished. Light L6 incident on side surface 1f occurs, for example, at an incident angle EA8. Light L6 can then be directed toward side surface 1c due to diffuse reflection at side surface 1f. Light L6 can be transmitted through side surface 1c. For comparison, Figure 6 also shows the path of light L7 incident on side surface 1f with a dashed line, assuming that side surface 1f is mirror-finished. Light L7 incident on side surface 1f at an incident angle EA8 undergoes total internal reflection at side surface 1f and is directed toward, for example, side surface 1e. Thereafter, light L7 is repeatedly reflected by, for example, sides 1f and 1e before being incident on side surface 1c and detected by the semiconductor photodetector 10. Light L7 undergoes greater reflection attenuation than light L6.

[0074] Figure 7 shows a partial path of scintillation light. In Figure 7, a partial path of scintillation light is shown when the scintillator 1 is viewed from a third direction D3. Figure 7 shows that the path from the generation point GP1 to the side surface 1c differs depending on the state of the end faces 1a and 1b of the scintillator 1. The semiconductor photodetector 10 is positioned facing the side surface 1c.

[0075] In the scintillator 1 used as an example in Figure 7, two end faces 1a and 1b are roughened. Two side faces 1c and 1d are mirror-finished. As shown in Figure 7, the scintillation light includes, in addition to light L1, light L8 incident from the generation point GP1 to side face 1d. 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. Since end face 1a is roughened, light L8 incident on end face 1a is directed towards side face 1c by diffuse reflection at end face 1a. The diffusely reflected light L8 can then be incident on side face 1c. Light L8 passes through side face 1c and is incident on the photodetection region 23a.

[0076] For comparison, Figure 7 shows the path of light L9 incident on end face 1a after total internal reflection at side surface 1d, assuming that end faces 1a and 1b are mirror-finished, with a dashed line. For example, light L9 incident on end face 1a at an incident angle EA10 is totally internally reflected at end face 1a. The light L9 that has been totally internally reflected at end face 1a may then be incident on end face 1b at an incident angle EA11, for example. The light L9 that has been incident on end face 1b is then totally internally reflected at end face 1b, for example. The light L9 that has been totally internally reflected at end face 1b is then incident on side surface 1c. Even if light L9 is transmitted through side surface 1c, the path from the point of origin GP1 of light L9 to side surface 1c is larger than the path from the point of origin GP1 of light L8 to side surface 1c. Light L8 is detected by the semiconductor photodetector 10 with a smaller time difference than light L9 compared to light L1. The amount of light L8 detected by the semiconductor photodetector 10 is greater than the amount of light L9 detected.

[0077] As shown in Figure 7, the scintillation light also includes, for example, light L10 incident from the point of origin GP1 to the end face 1b. The end face 1b is rough-finished. For example, light L10 incident on the end face 1b at an incident angle EA12 is directed toward the side surface 1c due to diffuse reflection at the end face 1b. Light L10 can be transmitted through the side surface 1c. For comparison, Figure 7 also shows the path of light L11 incident on the end face 1b with a dashed line, assuming that the end face 1b is mirror-finished. Light L11 incident on the end face 1b at an incident angle EA12 is totally reflected at the end face 1b and directed toward, for example, the end face 1a. Thereafter, light L11 is repeatedly reflected by the end faces 1b and 1a, for example, before being incident on the side surface 1c and detected by the semiconductor photodetector 10.

[0078] As shown in Figure 8, another side surface 1e adjacent to side surface 1c may be roughened. Figure 8 shows an example of the contour shape of another side surface. In Figure 8, an example of the contour shape of another side surface 1e is shown when the scintillator 1 is viewed from a first direction D1. In this embodiment, at least one of the roughened side surfaces 1e, 1f and end surfaces 1a, 1b has a contour shape as shown in Figure 8, for example.

[0079] If side surface 1e is roughened, then, for example, the cross-section of side surface 1e exhibits a triangular wave shape. The triangular wave shape of side surface 1e includes, for example, multiple edges 1j. Viewed from a first direction D1, the length W1 of each edge 1j is, for example, about 1.0 to 400 μm. Directions parallel to each edge 1j intersect each other. The angle TH1 at which each edge 1j intersects each other is, for example, about 20 to 160 degrees.

[0080] If side surface 1e is roughened, the cross-section of side surface 1e will exhibit a triangular wave shape when viewed from a second direction D2, for example. When viewed from a second direction D2, the length of each edge 1j is, for example, approximately 1.0 to 400 μm. When viewed from a second direction D2, the angle at which each edge 1j intersects with each other is, for example, approximately 20 to 160 degrees. The end faces 1a, 1b, and side surface 1f, when the end faces and side surfaces are roughened, exhibit a triangular wave shape, for example, as shown in Figure 8.

[0081] At least one of the roughened side surfaces 1e, 1f and end surfaces 1a, 1b is, for example, a rough surface. On these rough surfaces, the surface roughness is, for example, 0.5 to 200 μm. If 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 have to exhibit a triangular wave shape. In this specification, the maximum height (Rz) is used as the surface roughness of the surface. The maximum height (Rz) is defined in JIS B 0601:2001 (ISO 4287:1997).

[0082] In this embodiment, at least one of the sides 1e, 1f may be roughened, and at least one of the end faces 1a, 1b may be roughened. All of the sides 1e, 1f and end faces 1a, 1b may be roughened. The sides 1e, 1f may be mirror-finished, and at least one of the end faces 1a, 1b may be roughened. At least one of the sides 1e, 1f may be roughened, and the end faces 1a, 1b may be mirror-finished. All of the sides 1e, 1f and end faces 1a, 1b may be mirror-finished.

[0083] If at least one of the side surfaces 1c, 1d, 1e, 1f and the end surfaces 1a, 1b is, for example, mirror-finished, the surface roughness of the mirror-finished surface is, for example, 0.001 to 0.1 μm. For example, side surfaces 1c and 1d are mirror-finished.

[0084] A first modified example of the radiation detector RD1 according to the first embodiment will be described with reference to Figures 9 and 10. Figure 9 is a perspective view showing the radiation detector RD1 according to the first modified example of the first embodiment. Figure 10 is a diagram showing a portion of the path of scintillation light. In Figure 10, a portion of the path of scintillation light is shown with the scintillator 1 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.

[0085] The scintillator 1 according to this modified example 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, side faces 1c, 1d, and side faces 1e, 1f constitute the outer surface of the scintillator 1. In this modified example, unlike 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. 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 smaller than the length of the side face 1c in the first direction D1. The end faces 1a, 1b and the side faces 1c, 1d are rectangular in shape when viewed from a direction perpendicular to these faces, for example. The scintillator 1 is rectangular when viewed from a first direction D1 and a second direction D2. The first direction D1 is the longitudinal direction of the scintillator 1.

[0086] In this modified example, at least one of the sides 1e, 1f and the end faces 1a, 1b may be roughened. At least one of the sides 1e, 1f and the end face 1b may be roughened. The end face 1a does not have to be roughened. The sides 1c, 1d are, for example, mirror-finished. When viewed from the second direction D2, the photodetection region 23 has a contour shape corresponding to the contour shape of side 1c. In this modified example, when viewed from the second direction D2, the contour shape of side 1c is rectangular, and the photodetection region 23 has a rectangular contour shape corresponding to the contour shape of side 1c.

[0087] As shown in Figure 10, the scintillation light includes, for example, light L1 that is directly incident on the side surface 1c from the point of origin GP1. In addition to light L1, the scintillation light also includes light L12, which, for example, is initially incident on the side surface 1d and totally reflected by the side surface 1d. In this modified example, 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 is transmitted through the side surface 1c and detected by the semiconductor photodetector 10. Light reflectors 47 are arranged on the end surfaces 1a, 1b and the side surface 1d.

[0088] Scintillation light also includes, for example, light L13. Light L13, for example, is initially incident on side surface 1d, totally reflected by side surface 1d, and then incident on 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 totally reflected by side surface 1d, light L13 is incident on end surface 1b at an incident angle EA16. Although light L13 is incident on side surface 1d at the same incident angle as light L12, it is less likely to pass through side surface 1c as it is incident on end surface 1b, which extends in the second direction D2. Light L13 incident on end surface 1b is totally reflected at end surface 1b and incident on side surface 1c at an incident angle EA16a. In the example shown in Figure 10, the incident angle EA16a is greater than the critical angle at side surface 1c. Light L13 is totally reflected at side surface 1c. In the example shown in Figure 10, for example, if the incident angle EA15 is changed, light L13 may be totally reflected at end surface 1b and then incident at side surface 1c. This scintillation light totally reflected at end surface 1b is detected, for example, by a semiconductor photodetector 10.

[0089] A second modified example of the radiation detector RD1 according to the first embodiment will be described with reference to Figure 11. Figure 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.

[0090] The scintillator 1 according to this modified example 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, side faces 1c, 1d, and side faces 1e, 1f constitute the outer surface of the scintillator 1. In this modified example, unlike the first embodiment, 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 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 that the end face 1b makes with respect to the second direction D2 is, for example, 10 to 80 degrees counterclockwise. Viewed from a third direction D3, the sides 1e and 1f are, for example, trapezoidal. The length of side 1d in the first direction D1 is less than the length of side 1c in the first direction D1. The end faces 1a and 1b, and the sides 1c and 1d are rectangular when viewed from a direction perpendicular to these faces. The scintillator 1 is, for example, trapezoidal when viewed from a third direction D3, and rectangular when viewed from the first direction D1 and the second direction D2. The first direction D1 is the longitudinal direction of the scintillator 1.

[0091] In this modified example, at least one of the sides 1e, 1f and the end faces 1a, 1b may be given a rough finish. Sides 1c, 1d may be given a mirror finish, for example. When viewed from the second direction D2, the photodetection region 23 has a contour shape corresponding to the contour shape of side 1c. In this modified example, when viewed from the second direction D2, the contour shape of side 1c is rectangular, and the photodetection region 23 has a rectangular contour shape corresponding to the contour shape of side 1c.

[0092] Viewed from the third direction D3, the end faces 1a and 1b are inclined with respect to the second direction D2 so that scintillation light is easily totally reflected toward the side surface 1c. Scintillation light incident on end faces 1a and 1b is reflected by end faces 1a and 1b and then easily incident on the side surface 1c.

[0093] A third modified example of the radiation detector RD1 according to the first embodiment will be described with reference to Figures 12 and 13. Figure 12 is a perspective view showing the radiation detector RD1 according to the third modified example of the first embodiment. Figure 13 is a diagram showing a portion of the path of scintillation light. In Figure 13, a portion of the path of scintillation light is shown with the scintillator 1 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.

[0094] The scintillator 1 according to this modified example 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, side faces 1c, 1d, and side faces 1e, 1f constitute the outer surface of the scintillator 1. In this modified example, unlike the first embodiment, 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. Viewed from the third direction D3, the sides 1e and 1f have, for example, a parallelogram shape. The length of side 1d in the first direction D1 is approximately equal to the length of side 1c in the first direction D1. The end faces 1a and 1b, and the sides 1c and 1d, have a rectangular shape when viewed from a direction perpendicular to these faces. 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.

[0095] In this modified example, at least one of the sides 1e, 1f and the end faces 1a, 1b may be roughened. At least one of the sides 1e, 1f may be roughened. The end faces 1a, 1b do not need to be roughened. The sides 1c, 1d are, for example, mirror-finished. When viewed from the second direction D2, the photodetection region 23 has a contour shape corresponding to the contour shape of side 1c. In this modified example, when viewed from the second direction D2, the contour shape of side 1c is rectangular, and the photodetection region 23 has a rectangular contour shape corresponding to the contour shape of side 1c.

[0096] As shown in Figure 13, the scintillation light includes, for example, light L1 that is directly incident on the side surface 1c from the point of origin GP1. In addition to light L1, the scintillation light also includes light L14, which, for example, is initially incident on the side surface 1d at an incident angle EA13, is totally reflected by the side surface 1d, and then is incident on the end surface 1a at an incident angle EA14. The end surface 1a of this modified example has the same inclination as the end surface 1a of the first modified example of the first embodiment (see Figure 10), and light L14 travels along the same path as light L12 of the first modified example of the first embodiment. Light L14 is easily incident on the side surface 1c. Light L14 is transmitted through the side surface 1c and detected by the semiconductor photodetector 10. Light reflectors 47 are arranged on the end surfaces 1a, 1b and the side surface 1d.

[0097] The scintillation light also includes light L15, which, for example, is initially incident on the end face 1b at an incident angle EA17. In this modified example, the end face 1b is inclined with respect to the second direction D2. Light L15 is totally internalized by the end face 1b. The light L15 reflected by the end face 1b may, for example, be incident on the side surface 1d at an incident angle EA18. Light L15 is totally internalized at the side surface 1d and may be incident on the side surface 1c. The end face 1b is inclined with respect to the second direction D2 so that light L15 can easily be incident on the side surface 1c. Light L15 passes through the side surface 1c and, for example, is incident on the photodetection region 23d and detected by the semiconductor photodetector element 10.

[0098] A fourth modification of the radiation detector RD1 according to the first embodiment will be described with reference to Figures 14 and 15. Figure 14 is a perspective view showing the radiation detector RD1 according to the fourth modification of the first embodiment. Figure 15 is a diagram showing a portion of the path of scintillation light. In Figure 15, a portion of the path of scintillation light is shown with the scintillator 1 viewed from the first direction D1. The radiation detector RD1 according to this modification has the same configuration as the radiation detector RD1 according to the first embodiment, except for the configuration of the scintillator 1.

[0099] The scintillator 1 according to this modified example 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 so as to connect the end faces 1a, 1b. The end faces 1a, 1b and 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 so as to connect the end faces 1a, 1b. In this modified example, the end faces 1a, 1b extend in a 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 modified example, the direction perpendicular to side surface 1c coincides with the second direction D2, and the direction parallel to side surface 1c coincides with the third direction D3.

[0100] Viewed from the first direction D1, side surface 1g extends, for example, in the second direction D2. Side surface 1h is inclined, for example, with respect to the third direction D3. When end surface 1a is viewed in the first direction D1, the angle AG4 that side surface 1h makes with respect to the second direction D2 is, for example, 10 to 80 degrees counterclockwise. Viewed from the first direction D1, end surfaces 1a and 1b have a triangular shape, for example. Side surfaces 1c, 1g, and 1h have a rectangular shape when viewed from a direction perpendicular to these surfaces. The scintillator 1 has a triangular shape when viewed from the first direction D1, and a rectangular shape when viewed from the second direction D2 and the third direction D3.

[0101] In this modified example, at least one of the sides 1g, 1h and the end faces 1a, 1b may be roughened. At least one of the sides 1g and the end faces 1a, 1b may be roughened. Side 1h does not have to be roughened. At least one of the end faces 1a, 1b may be roughened. All of the sides 1g and the end faces 1a, 1b may be roughened. Side 1c is, for example, mirror-finished. Side 1h is inclined with respect to the second direction D2 so that scintillation light is easily totally reflected toward side 1c. Of the scintillation light, light incident on side 1h is easily reflected by side 1h and then incident on side 1c. Viewed from the second direction D2, the photodetection region 23 has a contour shape corresponding to the contour shape of side 1c. In this modified example, when viewed from the second direction D2, the contour shape of the side surface 1c is rectangular, and the photodetection region 23 exhibits a rectangular contour shape corresponding to the contour shape of the side surface 1c.

[0102] The length of scintillator 1 in the first direction D1 is greater than the length of scintillator 1 in the second direction D2. 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. The length of scintillator 1 in the first direction D1 is, for example, about 20 mm. The length of scintillator 1 in the second direction D2 is, for example, about 4 mm. The length of scintillator 1 in the third direction D3 is, for example, about 4 mm.

[0103] As shown in Figure 15, the scintillation light includes, for example, light L1 that is directly incident on side surface 1c from the point of origin GP1. In addition to light L1, the scintillation light also includes light L16, which, for example, is initially incident on side surface 1g at an incident angle EA19, is totally reflected by side surface 1g, and then incident on side surface 1c. Light L16 is transmitted through side surface 1c and detected by the semiconductor photodetector 10.

[0104] The scintillation light also includes light L17. Light L17, for example, 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 tilted with respect to the second direction D2. Light L17 can be totally reflected by side surface 1h and enter side surface 1c. Side surface 1h is tilted with respect to the second direction D2 to facilitate total internal reflection of light L17 toward side surface 1c. Light L17 is transmitted through side surface 1c and detected by the semiconductor photodetector 10.

[0105] A fifth modified example of the radiation detector RD1 according to the first embodiment will be described with reference to Figures 16 and 17. Figure 16 is a perspective view showing the radiation detector RD1 according to the fifth modified example of the first embodiment. Figure 17 is a plan view showing the semiconductor photodetector. 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 and the photodetector region 23.

[0106] As shown in Figure 16, the scintillator 1 according to this modified example has a pair of end faces 1a and 1b that face each other in the first direction D1, and side faces 1c, 1g, and 1h that extend in the first direction D1 so as to connect the end faces 1a and 1b. The end faces 1a and 1b and the side faces 1c, 1g, and 1h constitute the outer surface of the scintillator 1. The end faces 1a and 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 so as to connect the end faces 1a and 1b. In this modified example, unlike the fourth modified example 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 and 1g are adjacent to each other, and the side faces 1c and 1h are adjacent to each other. Sides 1g and 1h are adjacent to each other. The first direction D1 is the longitudinal direction of the scintillator 1. In this modified example, the direction perpendicular to side 1c coincides with the second direction D2, and the direction parallel to side 1c coincides with the third direction D3.

[0107] Viewed from the first direction D1, side surface 1g extends, for example, in the second direction D2. When end surface 1a is viewed in the first direction D1, side surface 1h forms an angle of, for example, 10 to 80 degrees counterclockwise with respect to the second direction D2. Viewed from the first direction D1, end surfaces 1a and 1b have a triangular shape, for example. Viewed from a direction perpendicular to these surfaces, side surfaces 1c and 1h have a rectangular shape. The scintillator 1 has a triangular shape, for example, when viewed from the first direction D1.

[0108] Viewed from the second direction D2, of the pair of edges 2a and 2b of the side surface 1c in the first direction D1, the edge 2a on the side of end face 1a forms an angle of, for example, 10 to 80 degrees counterclockwise with respect to the third direction D3. Viewed from the second direction D2, the edge 2b on the side of end face 1b extends in the third direction D3.

[0109] When viewed from the third direction D3, of the pair of edges 2c and 2d of the side surface 1g in the first direction D1, the edge 2d on the side of end face 1b extends in the second direction D2. When viewed from the third direction D3, the edge 2c on the side of end face 1a forms an angle of, for example, 10 to 80 degrees counterclockwise with respect to the second direction D2.

[0110] The length of scintillator 1 in the first direction D1 is greater than the length of scintillator 1 in the second direction D2. 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. At least one of side surfaces 1g, 1h, and end surfaces 1a, 1b may be roughened. At least one of side surface 1g and end surface 1b may be roughened. Side surfaces 1h and end surface 1b do not have to be roughened. Side surface 1c is, for example, mirror-finished.

[0111] As shown in Figure 17, when viewed from the second direction D2, the light detection region 23 has a contour shape that corresponds to the contour shape of the side surface 1c. Each light detection unit 15 is arranged such that, when viewed from the second direction D2, the light detection region 23 has a contour shape that corresponds to the contour shape of the side surface 1c.

[0112] In this modified example, the end face 1a is inclined with respect to the second direction D2 and the first direction D1 so that scintillation light is easily totally internalized toward the side surface 1c. Of the scintillation light, light incident on the end face 1a is easily reflected by the end face 1a and then incident on the side surface 1c. The side surface 1h is inclined with respect to the second direction D2 so that scintillation light is easily totally internalized toward the side surface 1c. Of the scintillation light, light incident on the side surface 1h is easily reflected by the side surface 1h and then incident on the side surface 1c.

[0113] A sixth modified example of the radiation detector RD1 according to the first embodiment will be described with reference to Figures 18 and 19. Figure 18 is a perspective view showing the radiation detector RD1 according to the sixth modified example of the first embodiment. Figure 19 is a plan view showing the semiconductor photodetector. 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 and the photodetector region 23.

[0114] The scintillator 1 according to this modified example has a pair of end faces 1a, 1b that face each other in a first direction D1, and side faces 1c, 1g, 1h that extend in the first direction D1 so as to connect the end faces 1a, 1b. The end faces 1a, 1b and 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 so as to connect the end faces 1a, 1b. In this modified example, the end faces 1a, 1b are inclined with respect to a 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 modified example, the direction perpendicular to side surface 1c coincides with the second direction D2, and the direction parallel to side surface 1c coincides with the third direction D3.

[0115] Viewed from the first direction D1, side surface 1g extends, for example, in the second direction D2. When end surface 1a is viewed in the first direction D1, side surface 1h forms an angle of, for example, 10 to 80 degrees counterclockwise with respect to the second direction D2. End surfaces 1a and 1b, when viewed from a direction perpendicular to these surfaces, exhibit, for example, a triangular shape, and side surface 1h, when viewed from a direction perpendicular to this surface, exhibits, for example, a rectangular shape. The scintillator 1, when viewed from the first direction D1, exhibits, for example, a triangular shape.

[0116] Viewed from the second direction D2, of the pair of edges 2a and 2b of the side surface 1c in the first direction D1, the edge 2a on the side of end face 1a forms an angle of, for example, 10 to 80 degrees counterclockwise with respect to the third direction D3. Viewed from the second direction D2, the edge 2b on the side of end face 1b forms an angle of, for example, 10 to 80 degrees clockwise with respect to the third direction D3.

[0117] When the side surface 1g is viewed in the third direction D3, of the pair of edges 2c and 2d of the side surface 1g in the first direction D1, the edge 2c on the side of end face 1a forms an angle of, for example, 10 to 80 degrees 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 end face 1b forms an angle of, for example, 10 to 80 degrees clockwise with respect to the second direction D2. When viewed from the third direction D3, the side surface 1g exhibits a trapezoidal shape, for example, and the distance between the edges 2c and 2d decreases as they move away from the side surface 1c. When viewed from the third direction D3, the side surface 1h exhibits a rectangular shape, for example.

[0118] The length of scintillator 1 in the first direction D1 is greater than the length of scintillator 1 in the second direction D2. 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. Viewed from the second direction D2, side surface 1c is, for example, trapezoidal, and the distance between edge 2a and edge 2b decreases as it moves away from side surface 1g.

[0119] As shown in Figure 19, when viewed from the second direction D2, the photodetection region 23 has a contour shape that corresponds to the contour shape of the side surface 1c. Each photodetection unit 15 is arranged such that, when viewed from the second direction D2, the photodetection region 23 has a contour shape that corresponds to the contour shape of the side surface 1c. In this modified example, when viewed from the second direction D2, the contour shape of the side surface 1c is trapezoidal, and the photodetection region 23 has a trapezoidal contour shape that corresponds to the contour shape of the side surface 1c.

[0120] In this modified example, end faces 1a and 1b are inclined with respect to the second direction D2 and the first direction D1 so that scintillation light is easily totally internalized toward side face 1c. Of the scintillation light, light incident on end faces 1a and 1b is easily reflected by end faces 1a and 1b and then incident on side face 1c. Side face 1h is inclined with respect to the second direction D2 so that scintillation light is easily totally internalized toward side face 1c. Of the scintillation light, light incident on side face 1h is easily reflected by side face 1h and then incident on side face 1c. In this modified example, at least one of the sides 1g, 1h and end faces 1a and 1b may be roughened. Only side face 1g may be roughened. Side face 1h and end faces 1a and 1b do not have to be roughened. Side face 1c may be, for example, mirror-finished.

[0121] A seventh modification of the radiation detector RD1 according to the first embodiment will be described with reference to Figures 20 and 21. Figure 20 is a perspective view showing the radiation detector RD1 according to the seventh modification of the first embodiment. Figure 21 is a plan view showing the semiconductor photodetector. The radiation detector RD1 according to this modification has the same configuration as the radiation detector RD1 according to the first embodiment, except for the configuration of the scintillator 1 and the photodetector region 23.

[0122] The scintillator 1 according to this modification has a pair of end faces 1a, 1b that face each other in a first direction D1, and side faces 1c, 1g, 1h that extend in the first direction D1 so as to connect the end faces 1a, 1b. The end faces 1a, 1b and 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 so as to connect the end faces 1a, 1b. The end faces 1a, 1b are inclined with respect to a 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 modified example, the direction perpendicular to side surface 1c coincides with the second direction D2, and the direction parallel to side surface 1c coincides with the third direction D3.

[0123] 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 in the first direction D1, the side surface 1g forms an angle of, for example, 10 to 80 degrees clockwise with respect to the second direction D2. Viewed from the first direction D1, the end surfaces 1a and 1b have a triangular shape. The scintillator 1 has a triangular shape when viewed from the first direction D1.

[0124] Viewed from the second direction D2, of the pair of edges 2a and 2b of the side surface 1c in the first direction D1, the edge 2a on the side of end face 1a forms an angle of, for example, 10 to 80 degrees clockwise with respect to the third direction D3. Viewed from the second direction D2, the edge 2b on the side of end face 1b forms an angle of, for example, 10 to 80 degrees clockwise with respect to the third direction D3.

[0125] As shown in Figure 21, when viewed from the second direction D2, the photodetection region 23 has a contour shape that corresponds to the contour shape of the side surface 1c. Each photodetection unit 15 is arranged such that, when viewed from the second direction D2, the photodetection region 23 has a contour shape that corresponds to the contour shape of the side surface 1c. In this modified example, when viewed from the second direction D2, the contour shape of the side surface 1c is a parallelogram, and the photodetection region 23 has a parallelogram contour shape that corresponds to the contour shape of the side surface 1c.

[0126] When the side surface 1h is viewed in the third direction D3, of the pair of edges 2e and 2f of the side surface 1h in the first direction D1, the edge 2e on the side of end face 1a 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 side of end face 1b 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 from the third direction D3, it presents a parallelogram shape, for example. When the side surface 1g is viewed from the third direction D3, it presents a rectangular shape, for example.

[0127] The length of scintillator 1 in the first direction D1 is greater than the length of scintillator 1 in the second direction D2. 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. In this modified example, end surfaces 1a, 1b and side surface 1g are inclined with respect to the second direction D2 so that scintillation light is easily totally reflected toward side surface 1c. At least one of side surfaces 1g, 1h and end surfaces 1a, 1b may be roughened. Only side surface 1h may be roughened. Side surfaces 1g and end surfaces 1a, 1b do not have to be roughened. Side surface 1c may be, for example, mirror-finished.

[0128] As described above, the radiation detector RD1 comprises a scintillator 1 having a pair of end faces 1a, 1b facing each other in a first direction D1 and a side surface 1c connecting the pair of end faces 1a, 1b; a semiconductor photodetector 10 having a semiconductor substrate 11 positioned facing the side surface 1c; and a wiring member 30 electrically connected to the semiconductor photodetector 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 surface 1c. The length of the side surface 1c in the first direction D1 is greater than the width of the side surface 1c in a third direction D3 perpendicular to both the first direction D1 and the second direction D2. The semiconductor substrate 11 has a first portion 21 covered by the side surface 1c and a second portion 22 aligned with the first portion 21 in the first direction D1 and exposed from the side surface 1c. The first part 21 has a photodetection region 23 having a plurality of avalanche photodiodes 12 operating in Geiger mode and a plurality of quenching resistors electrically connected in series with one of the anodes and cathodes of the corresponding avalanche photodiodes 12. The second part 22 has a first electrode 17 to which a plurality of quenching resistors 13 are connected in parallel and a second electrode 18 to which the other of the anodes and cathodes of the plurality of avalanche photodiodes 12 are connected in parallel. The wiring member 30 has a conductor electrically connected to the first electrode 17 and a conductor connected to the second electrode 18.

[0129] According to the radiation detector RD1, the radiation detector is equipped with a long scintillator 1 in the first direction D1, and a semiconductor photodetector 10 positioned on the side 1c of the scintillator 1. The semiconductor photodetector 10 not only detects the scintillation light from the scintillator 1 that is directly incident on the side 1c on which the semiconductor photodetector 10 is positioned, but also detects the scintillation light that is incident on side 1c after being reflected by another side 1d opposite to side 1c on which the semiconductor photodetector 10 is positioned. Since the length of the scintillator 1 in the second direction D2 is smaller than the length of the scintillator 1 in the first direction D1, the scintillation light that is directly incident on side 1c and the scintillation light that is incident on side 1c after being reflected by the other side 1d are detected by the semiconductor photodetector 10 with a small time difference. Therefore, the radiation detector RD1 achieves high temporal resolution. The length of the side surface 1c in the first direction D1 is greater than, for example, the length of the end surface 1b in the second direction D2. Therefore, compared to a configuration where, for example, the semiconductor photodetector 10 is positioned on the end surface 1b, it is possible to receive scintillation light incident on the side surface 1c at a larger incident angle EA1.

[0130] In the radiation detector RD1, the scintillator 1 appears rectangular or triangular when viewed from the first direction D1. In this case, scintillation light is reliably incident on the side surface 1c where the scintillator 1 is located. Therefore, the radiation detector RD1 reliably improves the amount of light received by the semiconductor photodetector 10.

[0131] In the radiation detector RD1, at least one of the pair of end faces 1a and 1b is inclined with respect to the second direction D2. In this case, scintillation light is more reliably incident on side surface 1c. The number of times the scintillation light is reflected by the end surfaces 1a, 1b or sides 1d, 1e, 1f, 1g, 1h is reduced, and the reflection attenuation is also reduced, so the radiation detector RD1 more reliably improves the amount of light received by the semiconductor photodetector 10.

[0132] In the radiation detector RD1, of the pair of end faces 1a and 1b, the end faces 1a and 1b that extend in the second direction D2 have a triangular wave shape in their cross-section. In this case, scintillation light is more reliably incident on side surface 1c. The number of times the scintillation light is reflected by the end surfaces 1a, 1b or sides 1d, 1e, 1f, 1g, 1h is reduced, and the reflection attenuation is also reduced, so the radiation detector RD1 more reliably improves the amount of light received by the semiconductor photodetector 10. When the cross-sections of the end faces 1a and 1b exhibit a triangular wave shape, the amount of light received by the semiconductor photodetector 10 is more reliably improved even without tilting the end faces 1a and 1b with respect to the second direction D2. In a configuration where the end faces 1a and 1b extend in the second direction D2, the amount of scintillator used is reduced compared to a configuration where the end faces 1a and 1b are tilted with respect to the second direction D2, allowing for the fabrication of the radiation detector RD1.

[0133] In the radiation detector RD1, of the pair of end faces 1a and 1b, the end faces 1a and 1b that extend in the second direction D2 are rough. In this case, scintillation light is more reliably incident on side surface 1c. The number of times the scintillation light is reflected by the end surfaces 1a, 1b or sides 1d, 1e, 1f, 1g, 1h is reduced, and the reflection attenuation is also reduced, so the radiation detector RD1 more reliably improves the amount of light received by the semiconductor photodetector 10.

[0134] In the radiation detector RD1, the scintillator 1 has a pair of end faces 1a and 1b connected together, and also has other side faces 1e, 1f, 1g, and 1h adjacent to side face 1c, which have a triangular wave cross-section. In this case, scintillation light is more reliably incident on side surface 1c. Therefore, the radiation detector RD1 more reliably improves the amount of light received by the semiconductor photodetector 10.

[0135] In the radiation detector RD1, the scintillator 1 has a pair of end faces 1a and 1b connected together, and also has other rough surfaces 1e, 1f, 1g, and 1h adjacent to side face 1c. In this case, scintillation light is more reliably incident on side surface 1c. Therefore, the radiation detector RD1 more reliably improves the amount of light received by the semiconductor photodetector 10.

[0136] In the radiation detector RD1, when viewed from the second direction D2, the photodetection region 23 exhibits a contour shape corresponding to the contour shape of the side surface 1c. In this case, the photodetector region 23 does not need to be placed in areas of the semiconductor substrate 11 that cannot receive scintillation light, thus suppressing the increase in dark count and capacitance in the photodetector region 23. Therefore, the radiation detector RD1 reliably improves the time resolution of the semiconductor photodetector element 10.

[0137] The radiation detector RD1 further includes a substrate 40 positioned between the scintillator 1 and the semiconductor substrate 11. The substrate 40 has a third portion covered by the semiconductor substrate 11 and a fourth portion aligned with the third portion in a first direction D1 and exposed from the semiconductor substrate 11. The fourth portion includes a first terminal 41 and a second terminal 42 positioned on the same side as the scintillator 1 with respect to the semiconductor substrate 11. The first terminal 41 is electrically connected by a first electrode 17 and a first wire 43, and the second terminal 42 is electrically connected by a second electrode 18 and 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.

[0138] In the radiation detector RD1, the first wire 43 and the second wire 44 are covered with resin 45. In this case, the first and second wires 43 and 44 are protected from damage. Therefore, this configuration suppresses deterioration of the electrical connection between the first and second terminals 41 and 42 and the first and second electrodes 17 and 18.

[0139] The radiation detector RD1 further includes a light reflector 47 positioned between the semiconductor substrate 11 and the scintillator 1. In this configuration, where one radiation detector RD1 is aligned with another radiation detector RD1 in the second direction D2, the light reflector 47 of one radiation detector RD1 improves the reflectivity of scintillation light on the other side 1d of the other radiation detector RD1 that faces side 1c in the second direction D2. The other side 1d of the other radiation detector RD1 has high reflectivity to scintillation light even in a configuration where the light reflector 47 is not present. Therefore, this configuration simplifies the configuration of the radiation detector RD1.

[0140] In the RD1 radiation detector, the thickness of the light reflector is 0.05 to 100 μm. In this case, the reflectivity of scintillation light on the other side 1d is reliably improved. Therefore, this configuration reliably simplifies the configuration of the radiation detector RD1.

[0141] In the radiation detector RD1, the wiring member 30 is located on the same side as the scintillator 1 with respect to the semiconductor substrate 11. In this case, for example, it is not necessary to prepare a new substrate for connecting the wiring member 30 to the first and second electrodes 17 and 18 by die bonding. Therefore, this configuration more reliably simplifies the configuration of the radiation detector. The configuration in which the wiring member 30 is located on the same side of the semiconductor substrate 11 as the scintillator 1 improves the space efficiency of the radiation detector RD1 compared to the configuration in which the wiring member 30 is located on the opposite side of the semiconductor substrate 11 from the scintillator 1.

[0142] In the radiation detector RD1, the wiring member 30 and the semiconductor substrate 11 are flexible. 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. Less force is applied to the semiconductor substrate 11 from the wiring member 30, and the semiconductor substrate 11 is less likely to suffer physical damage. Therefore, this configuration reliably maintains the mechanical strength of the radiation detector RD1.

[0143] (Second embodiment) The configuration of the radiation detector RD2 according to the second embodiment will be described with reference to Figures 22 and 23. In describing the radiation detector RD2, the differences from the radiation detector RD1 described above will be mainly explained, and common points may be omitted from the explanation.

[0144] Figure 22 is a perspective view showing a radiation detector RD2 according to the second embodiment. The radiation detector RD2 comprises a scintillator 1, a first semiconductor photodetector 10a, a second semiconductor photodetector 10b, a first wiring member 30a, and a second wiring member 30b. The first and second semiconductor photodetectors 10a and 10b detect scintillation light generated by the scintillator 1. The first semiconductor photodetector 10a has a first semiconductor substrate 11a and is electrically connected to the first wiring member 30a. The second semiconductor photodetector 10b has a second semiconductor substrate 11b and is electrically connected to the second wiring member 30b.

[0145] The scintillator 1 according to this embodiment has a pair of opposing end faces 1a, 1b, a pair of opposing side faces 1c, 1d, and a pair of opposing side faces 1e, 1f. 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, and the length of side face 1e in the first direction D1 is greater than the width of 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 in the third direction D3. The first direction D1 is the longitudinal direction of the scintillator 1. The second direction D2 is perpendicular to side face 1c, and the third direction D3 is perpendicular to side face 1e. For example, if side face 1c constitutes the first side face, then side face 1e constitutes the second side face.

[0146] 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 are rectangular when viewed from a direction perpendicular to these faces. The scintillator 1 is rectangular when viewed from the second direction D2 and the third direction D3. The scintillator 1 is also rectangular when viewed from the first direction D1. In this embodiment, the scintillator 1 has a rectangular parallelepiped shape.

[0147] At least one of the end faces 1a and 1b is, for example, roughened. Therefore, at least one of the end faces 1a and 1b has a triangular wave cross-section. At least one of the end faces 1a and 1b is, for example, roughened. The end faces 1a and 1b may be mirror-finished.

[0148] The first semiconductor substrate 11a is positioned facing side surface 1c. The second semiconductor substrate 11b is positioned facing side surface 1e. Side surface 1e is adjacent to side surface 1c. The first semiconductor substrate 11a has the same form and function as, for example, the semiconductor substrate 11 according to the first embodiment. The second semiconductor substrate 11b has the same form and function as, for example, the first semiconductor substrate 11a positioned on side surface 1c, except that it is positioned on side surface 1e. The first semiconductor substrate 11a is positioned on the first side surface 1c via, for example, an adhesive. The second semiconductor substrate 11b is positioned on the second side surface 1e via, for example, an adhesive.

[0149] The first semiconductor substrate 11a and the second semiconductor substrate 11b each 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 a 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 a first direction D1 and is exposed from the side surface 1c. The first portion 21 of the second semiconductor substrate 11b is covered by a 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 a first direction D1 and is exposed from the side surface 1e.

[0150] The first part 21 has a photodetection region 23. The photodetection region 23 has a plurality of avalanche photodiodes 12 and a plurality of quenching resistors 13. One photodetection unit 15 consists of one avalanche photodiode 12 and one quenching resistor 13 electrically connected in series with the corresponding avalanche photodiode 12. Multiple photodetection units 15 are arranged in the first part 21.

[0151] The second part 22 has a first electrode 17 and a second electrode 18. Multiple quenching resistors 13 are electrically connected in parallel to the first electrode 17 via a wire 14a. The multiple quenching resistors 13 are electrically connected in series to one of the anodes and cathodes of the corresponding avalanche photodiodes 12 from among the multiple avalanche photodiodes 12. The other of the anodes and cathodes of the multiple avalanche photodiodes 12 are electrically connected in parallel to the second electrode 18 via a wire 14b.

[0152] The first wiring member 30a is positioned on the same side as the scintillator 1 with respect to the first semiconductor substrate 11a. The second wiring member 30b is positioned on the same side as the scintillator 1 with respect to the second semiconductor substrate 11b. The first wiring member 30a has the same form and function as, for example, the wiring member 30 of the first embodiment. The second wiring member 30b has the same form and function as, for example, the first wiring member 30a which is electrically connected to the first semiconductor substrate 11a, except that it is electrically connected to the second semiconductor substrate 11b.

[0153] The first and second wiring members 30a and 30b each have a conductor 31 and a conductor 32, respectively. Conductor 31 is electrically connected to the first electrode 17, and 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.

[0154] Viewed from the second direction D2, the photodetection region 23 has a contour shape corresponding to the contour shape of the first side surface 1c. In this embodiment, viewed from the second direction D2, the contour shape of the first side surface 1c is rectangular, and the photodetection region 23 has a rectangular contour shape corresponding to the contour shape of the first side surface 1c. Viewed from the third direction D3, the photodetection region 23 has a contour shape corresponding to the contour shape of the second side surface 1e. In this embodiment, viewed from the third direction D3, the contour shape of the second side surface 1e is rectangular, and the photodetection region 23 has a rectangular contour shape corresponding to the contour shape of the second side surface 1e.

[0155] The radiation detector RD2 comprises a first substrate 40a and a second substrate 40b. The first substrate 40a is arranged such that a first semiconductor substrate 11a is located between the first substrate 40a and the scintillator 1. The second substrate 40b is arranged such that a second semiconductor substrate 11b is located between the second substrate 40b and the scintillator 1. The first substrate 40a has the same form and function as, for example, the substrate 40 according to the first embodiment. The second substrate 40b has the same form and function as, for example, the first substrate 40a.

[0156] The first substrate 40a and the second substrate 40b each have a third portion 51 and a fourth portion 52. The third portion 51 of the first substrate 40a is covered by the first semiconductor substrate 11a. The fourth portion 52 of the first substrate 40a is aligned with the third portion 51 of the first substrate 40a in the first direction D1 and is exposed from the first semiconductor substrate 11a. The third portion 51 of the second substrate 40b is covered by the second semiconductor substrate 11b. The fourth portion 52 of the second substrate 40b is aligned with the third portion 51 of the second substrate 40b in the first direction D1 and is exposed from the second semiconductor substrate 11b.

[0157] The fourth portion 52 of the first substrate 40a and the second substrate 40b includes a first terminal 41 and a second terminal 42. The first terminal 41 and the second terminal 42 of the first substrate 40a are located on the same side as, for example, the scintillator 1 with respect to the first semiconductor substrate 11a. The first terminal 41 and the second terminal 42 of the second substrate 40b are located on the same side as, for example, the scintillator 1 with respect to the second semiconductor substrate 11b. The first terminal 41 of the first substrate 40a and the second substrate 40b is electrically connected by a first electrode 17 and a first wire 43, and the second terminal 42 of the first substrate 40a and the second substrate 40b is electrically connected by a second electrode 18 and a second wire 44. The radiation detector RD2 does not have to include either the first substrate 40a or the second substrate 40b, nor does it have to include both the first substrate 40a and the second substrate 40b.

[0158] 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, they may be spaced apart from each other or connected to each other.

[0159] The radiation detector RD2 includes, for example, a first light reflector 47a and a second light reflector 47b. The first light reflector 47a is positioned such that a first semiconductor substrate 11a is located between the first light reflector 47a and the scintillator 1. The second light reflector 47b is positioned such that a 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 a first base 40a, the first light reflector 47a is positioned such that a 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 a 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 where the radiation detector RD2 includes a second substrate 40b, the second light reflector 47b is positioned such that the second semiconductor substrate 11b and the second substrate 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 substrate 40b, and the second light reflector 47b are arranged in this order. In a configuration where the radiation detector RD2 does not include a second substrate 40b, the scintillator 1, the second semiconductor substrate 11b, and the second light reflector 47b are arranged in this order. The radiation detector RD2 may not include either the first light reflector 47a or the second light reflector 47b.

[0160] The first and second light reflectors 47a and 47b are made of the same material as the light reflector 47 according to the first embodiment and have the same shape. The thickness of the first and second light reflectors 47a and 47b is, for example, 0.05 to 100 μm.

[0161] Figure 23 shows a partial path of scintillation light. In Figure 23, a partial path of scintillation light is shown with the scintillator 1 viewed from a first direction D1. The scintillation light includes, for example, light L18 and light L19 incident on side surface 1c from the generation point GP1. Light L18 is incident on side surface 1c at an incident angle EA21, and light L19 is incident on side surface 1c at an incident angle EA22. For example, the incident angle EA21 is smaller than the critical angle at side surface 1c, and the incident angle EA22 is larger than the critical angle at side surface 1c. In this embodiment, the first and second semiconductor photodetectors 10a and 10b can be bonded to the scintillator 1 with an adhesive having the same refractive index, so the critical angle at side surface 1e is equal to the critical angle at side surface 1c.

[0162] As shown in Figure 23, light L18 is incident on side surface 1c at an incident angle EA21 and passes through side surface 1c. Light L18 is detected by the first semiconductor photodetector 10a located on side surface 1c. Light L19 is incident on side surface 1c at an incident angle EA22 and is totally reflected by side surface 1c. Light L19 is difficult to detect by the first semiconductor photodetector 10a located on side surface 1c. However, after light L19 is totally reflected by side surface 1c, it is incident on side surface 1e, for example. There is a case where the incident angle EA23 of light L19 incident on side surface 1e is smaller than the critical angle at side surface 1e. In this case, light L19 passes through side surface 1e and is detected by the second semiconductor photodetector 10b located on side surface 1e. In other words, even if the angle of incidence to side surface 1c exceeds the critical angle and the scintillation light is not detected by the first semiconductor photodetector 10a located on side surface 1c, the scintillation light is detected by the second semiconductor photodetector 10b located on side surface 1e, which is adjacent to side surface 1c.

[0163] For example, the incident angle EA23 is 90 degrees minus the incident angle EA22. For instance, when the incident angle EA22 is 60 degrees or more, the incident angle EA23 is 30 degrees or less. As mentioned above, if the refractive index of scintillator 1 is 1.8 and the refractive index of the adhesive used to bond the first and second semiconductor photodetectors 10a and 10b to sides 1c and 1e, respectively, is 1.5, then the critical angle at sides 1c and 1e is approximately 56.4 degrees. In this case, scintillation light with an incident angle EA22 of 60 degrees or more will be totally reflected by side 1c even if it is incident on side 1c. However, if it is incident on side 1e, which is adjacent to side 1c, the scintillation light will pass through side 1e and be detected by the second semiconductor photodetector 10b located on side 1e. When the incident angle EA22 of the scintillation light is, for example, 50 degrees or less, the scintillation light passes through the side surface 1c and is detected by the second semiconductor photodetector element 10b located on the side surface 1c.

[0164] A first modified example of the radiation detector RD2 according to the second embodiment will be described with reference to Figure 24. Figure 24 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 configuration of the scintillator 1 and the photodetection region 23.

[0165] The scintillator 1 according to this modified example 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, side faces 1c, 1d, and side faces 1e, 1f constitute the outer surface of the scintillator 1. In this modified example, 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 modified example, the direction perpendicular to side face 1c coincides with the second direction D2, and the direction perpendicular to side face 1e coincides with the third direction D3. The first direction D1 is the longitudinal direction of the scintillator 1. Viewed from the first direction D1, the end faces 1a, 1b have a rectangular shape. Scintillator 1, for example, has a rectangular shape when viewed from the first direction D1.

[0166] 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 also inclined with respect to the third direction D3. Edges 2a and 2g extend approximately parallel to each other when viewed from the second direction D2. When viewed from the second direction D2, edges 2a and 2g form an angle of, for example, 10 to 80 degrees counterclockwise with respect to the third direction D3. 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.

[0167] In this modified example, when viewed from the second direction D2, the photodetection region 23 has a contour shape corresponding to the contour shape of the first side surface 1c. Each photodetection unit 15 is arranged such that, when viewed from the second direction D2, the photodetection region 23 has a contour shape corresponding to the contour shape of the first side surface 1c. When viewed from the third direction D3, the photodetection region 23 has a contour shape corresponding to the contour shape of the second side surface 1e. Each photodetection unit 15 is arranged such that, when viewed from the third direction D3, the photodetection region 23 has a contour shape corresponding to the contour shape of the second side surface 1e.

[0168] 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 also inclined with respect to the second direction D2. Edges 2i and 2j extend approximately parallel to each other when viewed from the third direction D3. When the side surface 1f is viewed from the third direction D3, edges 2i and 2j form an angle of, for example, 10 to 80 degrees clockwise with respect to the second direction D2.

[0169] 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 the scintillator in the third direction D3. At least one of the end faces 1a and 1b is, for example, roughened. Only end face 1b may be roughened, and end face 1a may not be roughened. Side surfaces 1c and 1e are, for example, mirror-finished.

[0170] In this modified example, the end face 1a is inclined with respect to the second direction D2 and the third direction D3 so that scintillation light is easily totally reflected toward the sides 1c and 1e. Of the scintillation light, the light incident on the end face 1a is reflected by the end face 1a and then easily incident on the sides 1c and 1e.

[0171] A second modified example of the radiation detector RD2 according to the second embodiment will be described with reference to Figure 25. Figure 25 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 configuration of the scintillator 1 and the photodetection region 23.

[0172] The scintillator 1 according to this modified example 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 constitute the outer surface of the scintillator 1. In this modified example, unlike the second embodiment, the end faces 1a, 1b are inclined with respect to the second direction D2 and the third direction D3. In this modified example, the direction perpendicular to side face 1c coincides with the second direction D2, and the direction perpendicular to 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. The scintillator 1 has a rectangular shape when viewed from the first direction D1, for example.

[0173] 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 also inclined with respect to the third direction D3. Edges 2a and 2g extend approximately parallel to each other when viewed from the second direction D2. When viewed from the second direction D2, edges 2a and 2g form an angle of, for example, 10 to 80 degrees counterclockwise with respect to the third direction D3.

[0174] Viewed from the second direction D2, the edge 2b of the side surface 1c on the end face 1b side is inclined with respect to the third direction D3, and the edge 2h of the side surface 1d on the end face 1b side is also inclined with respect to the third direction D3. Edges 2b and 2h extend approximately parallel to each other when viewed from the second direction D2. When viewed from the second direction D2, edges 2b and 2h form an angle of, for example, 10 to 80 degrees clockwise with respect to the third direction D3. When viewed from the second direction D2, sides 1c and 1d exhibit, for example, a trapezoidal shape.

[0175] The photodetection region 23 exhibits a contour shape that corresponds to the contour shape of the first side surface 1c when viewed from the second direction D2. In this modified example, when viewed from the second direction D2, the contour shape of the side surface 1c is trapezoidal, and the photodetection region 23 exhibits a trapezoidal contour shape that corresponds to the contour shape of the first side surface 1c.

[0176] 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 also inclined with respect to the second direction D2. Edges 2i and 2j extend approximately parallel to each other when viewed from the third direction D3. When the side surface 1f is viewed from the third direction D3, edges 2i and 2j form an angle of, for example, 10 to 80 degrees clockwise with respect to the second direction D2.

[0177] Viewed from the third direction D3, the edge 2k of side surface 1e on end face 1b is inclined with respect to the second direction D2, and the edge 2m of side surface 1f on end face 1b is also inclined with respect to the second direction D2. Edges 2k and 2m extend approximately parallel to each other when viewed from the third direction D3. When side surface 1f is viewed from the third direction D3, edges 2k and 2m form an angle of, for example, 10 to 80 degrees counterclockwise with respect to the second direction D2. Viewed from the third direction D3, sides 1e and 1f exhibit, for example, a trapezoidal shape.

[0178] Viewed from the third direction D3, the photodetection region 23 exhibits a contour shape corresponding to the contour shape of the second side surface 1e. In this modified example, viewed from the third direction D3, the contour shape of the second side surface 1e is trapezoidal, and the photodetection region 23 exhibits a trapezoidal contour shape corresponding to the contour shape of the second side surface 1e.

[0179] 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 the scintillator in the third direction D3.

[0180] At least one of the end faces 1a and 1b is, for example, roughened. Therefore, at least one of the end faces 1a and 1b has a triangular wave cross-section. At least one of the end faces 1a and 1b is, for example, roughened. The end faces 1a and 1b may be mirror-finished. The side surfaces 1c and 1e are, for example, mirror-finished.

[0181] In this modified example, the end faces 1a and 1b are inclined with respect to the second direction D2 and the third direction D3 so that scintillation light is easily totally reflected toward the side faces 1c and 1e. Of the scintillation light, the light incident on the end faces 1a and 1b is reflected by the end faces 1a and 1b, respectively, and then easily incident on the side faces 1c and 1e.

[0182] A third modified example of the radiation detector RD2 according to the second embodiment will be described with reference to Figure 26. Figure 26 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 configuration of the scintillator 1 and the photodetection region 23.

[0183] The scintillator 1 according to this modified example 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 constitute the outer surface of the scintillator 1. In this modified example, unlike the second embodiment, the end faces 1a, 1b are inclined with respect to the second direction D2 and the third direction D3. In this modified example, the direction perpendicular to side face 1c coincides with the second direction D2, and the direction perpendicular to 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. The scintillator 1 has a rectangular shape when viewed from the first direction D1, for example.

[0184] 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 also inclined with respect to the third direction D3. Edges 2a and 2g extend approximately parallel to each other when viewed from the second direction D2. When viewed from the second direction D2, edges 2a and 2g form an angle of, for example, 10 to 80 degrees counterclockwise with respect to the third direction D3.

[0185] Viewed from the second direction D2, the edge 2b of the side surface 1c on the end face 1b side is inclined with respect to the third direction D3, and the edge 2h of the side surface 1d on the end face 1b side is also inclined with respect to the third direction D3. The edges 2b and 2h extend approximately parallel to each other when viewed from the second direction D2. When viewed from the second direction D2, the edges 2b and 2h form an angle of, for example, 10 to 80 degrees counterclockwise with respect to the third direction D3.

[0186] The light detection region 23 has a contour shape that corresponds to the contour shape of the first side surface 1c when viewed from the second direction D2. In this modified example, when viewed from the second direction D2, the contour shape of the first side surface 1c is a parallelogram, and the light detection region 23 has a parallelogram contour shape that corresponds to the contour shape of the first side surface 1c.

[0187] 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 also inclined with respect to the second direction D2. Edges 2i and 2j extend approximately parallel to each other when viewed from the third direction D3. When the side surface 1f is viewed from the third direction D3, edges 2i and 2j form an angle of, for example, 10 to 80 degrees clockwise with respect to the second direction D2.

[0188] Viewed from the third direction D3, the edge 2k of side surface 1e on end face 1b is inclined with respect to the second direction D2, and the edge 2m of side surface 1f on end face 1b is also inclined with respect to the second direction D2. Edges 2k and 2m extend approximately parallel to each other when viewed from the third direction D3. When side surface 1f is viewed from the third direction D3, edges 2k and 2m form an angle of, for example, 10 to 80 degrees clockwise with respect to the second direction D2. Viewed from the third direction D3, sides 1e and 1f exhibit, for example, a parallelogram shape.

[0189] Viewed from the third direction D3, the photodetection region 23 exhibits a contour shape corresponding to the contour shape of the second side surface 1e. In this modified example, viewed from the third direction D3, the contour shape of the second side surface 1e is a parallelogram, and the photodetection region 23 exhibits a parallelogram contour shape corresponding to the contour shape of the second side surface 1e.

[0190] 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 the scintillator in the third direction D3. The end faces 1a and 1b do not need to be roughened. Side surfaces 1c and 1e are, for example, mirror-finished.

[0191] In this modified example, the end faces 1a and 1b are inclined with respect to the second direction D2 and the third direction D3 so that scintillation light is easily totally reflected toward the side faces 1c and 1e. Of the scintillation light, the light incident on the end faces 1a and 1b is reflected by the end faces 1a and 1b, respectively, and then easily incident on the side faces 1c and 1e.

[0192] As described above, the radiation detector RD2 comprises a scintillator 1 which is rectangular in shape when viewed from a first direction D1 and has a pair of end faces 1a, 1b facing each other in the first direction D1, a first side surface 1c connecting the pair of end faces 1a, 1b, and a second side surface 1e which connects the pair of end faces 1a, 1b and is adjacent to the first side surface 1c; a first semiconductor photodetector 10a which has a first semiconductor substrate 11a which is arranged to face the first side surface 1c; a second semiconductor photodetector 10b which has a second semiconductor substrate 11b which is arranged to face the second side surface 1e; a first wiring member 30a which is electrically connected to the first semiconductor photodetector 10a; and a second wiring member 30b which is electrically connected to the second semiconductor photodetector 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 which is perpendicular to the first side surface 1c and the length of the scintillator 1 in the third direction D3 which is perpendicular to the second side surface 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, and 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 have a first portion 21 covered by either the corresponding first side surface 1c or the second side surface 1e, 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 the second side surface 1e. The first portion 21 has a photodetection region 23 having a plurality of avalanche photodiodes 12 operating in Geiger mode, and a plurality of quenching resistors 13 electrically connected in series with either the anode or cathode of a corresponding avalanche photodiode 12. The second part 22 includes a first electrode 17 to which multiple quenching resistors 13 are connected in parallel, and a second electrode 18 to which the other ends of the anodes and cathodes of multiple avalanche photodiodes 12 are connected in parallel. The first wiring member 30a and the second wiring member 30b have a conductor 31 that is electrically connected to the first electrode 17 and a conductor 32 that is connected to the second electrode 18.

[0193] In this embodiment, the radiation detector RD2 includes a long scintillator 1 in the first direction D1, and a first semiconductor photodetector 10a positioned on the first side surface 1c of the scintillator 1. The first semiconductor photodetector 10a not only detects scintillation light that directly incident on the first side surface 1c on which the first semiconductor photodetector 10a is positioned, but also detects scintillation light that is reflected by, for example, the side surface 1d opposite to the first side surface 1c on which the first semiconductor photodetector 10a is positioned, and then incident on the first side surface 1c. Since the length of the scintillator 1 in the second direction D2 is smaller than the length of the scintillator 1 in the first direction D1, the scintillation light that 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 photodetector 10a with a small time difference. Therefore, the radiation detector RD2 achieves high temporal resolution. According to the radiation detector RD2, even if the angle of incidence of scintillation light onto the first side surface 1c exceeds the critical angle at the first side surface 1c and is not detected by the first semiconductor photodetector 10a located on the first side surface 1c, the scintillation light is still detected by the second semiconductor photodetector 10b located on the second side surface 1e, which is adjacent to the first side surface 1c. Therefore, the radiation detector RD2 realizes a radiation detector with high temporal resolution and reliably improves the amount of light received by the first and second semiconductor photodetectors 10a and 10b.

[0194] 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, scintillation light is more reliably incident on the first side surface 1c and the second side surface 1e. As the number of times the scintillation light is reflected by the end faces 1a, 1b or the side surfaces decreases, and the reflection attenuation is also reduced, the radiation detector RD2 more reliably improves the amount of light received by the first and second semiconductor photodetectors 10a and 10b.

[0195] In the radiation detector RD2, of the pair of end faces 1a and 1b, the end faces 1a and 1b that extend in the second direction D2 have a triangular wave shape in their cross-section. In this case, scintillation light is more reliably incident on the first side surface 1c and the second side surface 1e. As the number of times the scintillation light is reflected by the end faces 1a, 1b or the side surfaces decreases and the reflection attenuation is also reduced, the radiation detector RD2 more reliably improves the amount of light received by the first and second semiconductor photodetectors 10a and 10b. When the cross-sections of the end faces 1a and 1b exhibit a triangular wave shape, the amount of light received by the first and second semiconductor photodetectors 10a and 10b is more reliably improved even without tilting the end faces 1a and 1b with respect to the second direction D2. In a configuration where the end faces 1a and 1b extend in the second direction D2, the amount of scintillator 1 used is reduced compared to a configuration where the end faces 1a and 1b are tilted with respect to the second direction D2, allowing for the fabrication of the radiation detector RD2.

[0196] In the radiation detector RD2, at least one of the pair of end faces 1a and 1b is rough. In this case, scintillation light is more reliably incident on the first side surface 1c and the second side surface 1e. As the number of times the scintillation light is reflected by the end faces 1a, 1b or the side surfaces decreases and the reflection attenuation is also reduced, the radiation detector RD2 more reliably improves the amount of light received by the first and second semiconductor photodetectors 10a and 10b. When the cross-sections of the end faces 1a and 1b are rough, the amount of light received by the first and second semiconductor photodetectors 10a and 10b is more reliably improved even without tilting the end faces 1a and 1b with respect to the second direction D2. In a configuration where the end faces 1a and 1b extend in the second direction D2, the amount of scintillator 1 used is reduced compared to a configuration where the end faces 1a and 1b are tilted with respect to the second direction D2, and the radiation detector RD2 is fabricated.

[0197] In the radiation detector RD2, when viewed from the second direction D2, the photodetection region 23 exhibits a contour shape corresponding to the contour shape of the first side surface 1c. Each photodetector 15 is arranged such that, when viewed from the second direction D2, the photodetection region 23 exhibits a contour shape corresponding to the contour shape of the first side surface 1c. When viewed from the third direction D3, the photodetection region 23 exhibits a contour shape corresponding to the contour shape of the second side surface 1e. Each photodetector 15 is arranged such that, when viewed from the third direction D3, the photodetection region 23 exhibits a contour shape corresponding to the contour shape of the second side surface 1e. In this case, the photodetector region 23 does not need to be placed in the areas of the first and second semiconductor substrates 11a and 11b that cannot receive scintillation light, thus suppressing the increase in dark count and capacitance in the photodetector region 23. Therefore, the radiation detector RD2 reliably improves the time resolution of the first and second semiconductor photodetectors 10a and 10b.

[0198] The radiation detector RD2 further comprises a first substrate 40a positioned between itself and the scintillator 1 such that a first semiconductor substrate 11a is located between itself and the scintillator 1, and a second substrate 40b positioned between itself and the scintillator 1 such that a second semiconductor substrate 11b is located between itself and the scintillator 1. The first substrate and the second substrates 40a and 40b each have a third portion covered by the first semiconductor substrate 11a and the second semiconductor substrate 11b, and a fourth portion aligned with the third portion in a first direction D1 and exposed from the first semiconductor substrate 11a and the second semiconductor substrate 11b. Each fourth portion includes a first terminal 41 and a second terminal 42 positioned on the same side as the scintillator 1 with respect to the corresponding first semiconductor substrate 11a or second semiconductor substrate 11b. The first terminal 41 is electrically connected by a first electrode 17 and a first wire 43, and the second terminal 42 is electrically connected by a second electrode 18 and 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.

[0199] In the radiation detector RD2, the first wire 43 and the second wire 44 are covered with resin 45. In this case, the resin 45 protects the first and second wires 43 and 44, making them less susceptible to damage. Therefore, this configuration suppresses deterioration of the electrical connection between the first and second terminals 41 and 42 and the first and second electrodes 17 and 18.

[0200] The radiation detector RD2 further includes a first light reflector 47a positioned between it and the scintillator 1 such that the first semiconductor substrate 11a is located between it and the scintillator 1, and a second light reflector 47b positioned between it and the second semiconductor substrate 11b is located between it and the scintillator 1. In this configuration, when one radiation detector RD2 and the other radiation detector RD2 are arranged in the second direction D2, the first light reflector 47a improves the reflectivity of scintillation light on the other side 1d of the adjacent radiation detector RD2 in the second direction D2. The other side 1d of the other radiation detector RD2 has high reflectivity to scintillation light even in a configuration without the first light reflector 47a. When one radiation detector RD2 and the other radiation detector RD2 are arranged in the third direction D3, the second light reflector 47b improves the reflectivity of scintillation light on the other side 1f of the adjacent radiation detector RD2 in the third direction D3. The other side 1f of the other radiation detector RD2 has high reflectivity to scintillation light even in a configuration without the second light reflector 47b. Therefore, this configuration certainly simplifies the configuration of the radiation detector RD2.

[0201] In the RD2 radiation detector, the thickness of the first and second light reflectors is 0.05 to 100 μm. In this case, the reflectivity of scintillation light on the other sides 1d and 1f is reliably improved. Therefore, this configuration reliably simplifies the configuration of the radiation detector RD2.

[0202] In the radiation detector RD2, the first wiring member 30a is located on the same side as the scintillator 1 with respect to the first semiconductor substrate 11a. The second wiring member 30b is located on the same side as the scintillator 1 with respect to the second semiconductor substrate 11b. In this case, for example, it is not necessary to prepare new substrates for connecting the first and second wiring members 30a and 30b to the first and second electrodes 17 and 18, respectively, by die bonding. Therefore, this configuration more reliably simplifies the configuration of the radiation detector RD2. The configuration in which the first and second wiring members 30a and 30b are located on the same side as the scintillator 1 with respect to the first and second semiconductor substrates 11a and 11b, respectively, improves the space efficiency of the radiation detector RD2 compared to a configuration in which the first and second wiring members 30a and 30b are located on the opposite side of the scintillator 1 with respect to the first and second semiconductor substrates 11a and 11b, respectively.

[0203] 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 and 30b to the first and second semiconductor substrates 11a and 11b. Forces from the first and second wiring members 30a and 30b are less likely to be applied to the first and second semiconductor substrates 11a and 11b, respectively, and the first and second semiconductor substrates 11a and 11b are less likely to suffer physical damage. Therefore, this configuration reliably maintains the mechanical strength of the radiation detector RD2.

[0204] (Third embodiment) The configuration of the radiation detector array RA1 according to the third embodiment will be described with reference to Figure 27. Figure 27 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.

[0205] Each of the multiple radiation detectors RD1 is, for example, arranged in a second direction D2 and further arranged in a third direction D3. In the example shown in Figure 27, six radiation detectors RD1 of the first embodiment are arranged in the second direction D2 and six are also arranged in the third direction D3. The radiation detector array RA1 is composed of, for example, a total of 36 radiation detectors RD1.

[0206] The end face 1a of one radiation detector RD1 is flush with the end face 1a of another adjacent radiation detector RD1 in the second direction D2 or the third direction D3. The semiconductor photodetector 10 of one radiation detector RD1 is aligned with the semiconductor photodetector 10 of another adjacent radiation detector RD1 in the third direction D3. Each semiconductor photodetector 10 adjacent in the third direction D3 is formed integrally with each other, for example. Each semiconductor photodetector 10 adjacent in the third direction D3 does not have to be formed integrally with each other.

[0207] The radiation detector array RA1 may consist of radiation detectors RD1 according to any one of the first to seventh modifications of the first embodiment, in addition to the radiation detector RD1 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 that is adjacent in the third direction D3. Each semiconductor photodetector element 10 adjacent in the third direction D3 is formed integrally with each other, for example. Each semiconductor photodetector element 10 adjacent in the third direction D3 is not required to be formed integrally with each other.

[0208] As described above, the radiation detector array RA1 is a radiation detector array RA1 in which a plurality of radiation detectors RD1 are arranged in a matrix in a two-dimensional manner when viewed from a first direction D1, and each of the plurality of radiation detectors RD1 is a radiation detector RD1 according to the first embodiment described above, and the semiconductor photodetector element 10 of one radiation detector RD1 is aligned with the semiconductor photodetector element 10 of another radiation detector RD1 that is adjacent to it in a direction parallel to the side surface 1c.

[0209] According to this embodiment, a radiation detector array RA1 is realized in which radiation detectors RD1 having high temporal resolution are arranged in a matrix in a two-dimensional manner. Since one radiation detector RD1 is equipped with, for example, a light reflector 47, the other side 1d of an adjacent radiation detector RD1 has a high reflectivity to scintillation light, even if it does not have a light reflector 47. Since the radiation detector RD1 has a configuration in which no additional light reflector 47 is placed on the other side 1d, the spacing between radiation detectors RD1 in the second direction D2 is reduced in the radiation detector array RA1.

[0210] In the radiation detector array RA1, each semiconductor photodetector 10 adjacent to each other in the direction parallel to the side surface 1c, i.e., in the third direction D3, is integrally formed with respect to each other. In this case, when fabricating a radiation detector array RA1 in which multiple radiation detectors RD1 are arranged in a matrix in a two-dimensional manner, the process of forming the semiconductor photodetector element 10 is simplified.

[0211] (Fourth embodiment) The configuration of the radiation detector array RA2 according to the fourth embodiment will be described with reference to Figure 28. Figure 28 is a perspective view showing the radiation detector array RA2 according to the fourth embodiment. The radiation detector array RA2 is configured by arranging a plurality of radiation detectors RD2 according to the second embodiment in a two-dimensional matrix.

[0212] Each of the multiple radiation detectors RD2 is, for example, arranged in a second direction D2 and further arranged in a third direction D3. In the example shown in Figure 28, six radiation detectors RD2 of the second embodiment are arranged in the second direction D2 and six are also arranged in the third direction D3. The radiation detector array RA2 consists of, for example, a total of 36 radiation detectors RD1.

[0213] The end face 1a of one radiation detector RD2 is flush with the end face 1a of another adjacent radiation detector RD2 in the second direction D2 or the third direction D3. The first semiconductor photodetector 10a of one radiation detector RD2 is aligned with the first semiconductor photodetector 10a of another adjacent radiation detector RD2 in the third direction D3. The second semiconductor photodetector 10b of one radiation detector RD2 is aligned with the second semiconductor photodetector 10b of yet another adjacent radiation detector RD2 in the second direction D2. Each first semiconductor photodetector 10a adjacent in the third direction D3 is, for example, formed integrally with each other. Each second semiconductor photodetector 10b adjacent in the second direction D2 is, for example, formed integrally with each other.

[0214] The radiation detector array RA2 may consist of any of the first to third modified examples of the second embodiment, in addition to the radiation detector RD2 of the second embodiment. In this case as well, the first semiconductor photodetector 10a of one radiation detector RD2 is aligned with the first semiconductor photodetector 10a of another radiation detector RD2 adjacent in the third direction D3. The second semiconductor photodetector 10b of one radiation detector RD2 is aligned with the second semiconductor photodetector 10b of yet another radiation detector RD2 adjacent in the second direction D2. Each first semiconductor photodetector 10a adjacent in the third direction D3 is, for example, formed integrally with each other. Each second semiconductor photodetector 10b adjacent in the second direction D2 is, for example, formed integrally with each other. Each first semiconductor photodetector 10a adjacent in the third direction D3 is not required to be formed integrally with each other. Each second semiconductor photodetector 10b adjacent in the second direction D2 is not required to be formed integrally with each other.

[0215] As described above, the radiation detector array RA2 is a radiation detector array RA2 in which a plurality of radiation detectors RD2 are arranged in a matrix in a two-dimensional manner when viewed from the first direction D1, and each of the plurality of radiation detectors RD2 is a radiation detector RD2 according to the second embodiment described above, the first semiconductor photodetector element 10a of one radiation detector RD2 is aligned with the first semiconductor photodetector element 10a of another radiation detector RD2 adjacent in the third direction D3, and the second semiconductor photodetector element 10b of one radiation detector RD2 is aligned with the second semiconductor photodetector element 10b of yet another radiation detector RD2 adjacent in the second direction D2.

[0216] According to this embodiment, a radiation detector array RA2 is realized in which radiation detectors RD2 having high temporal resolution are arranged in a matrix in a two-dimensional manner. Since one radiation detector RD2 is equipped with, for example, first and second light reflectors 47a and 47b, the other sides 1d and 1f of an adjacent radiation detector RD1 have high reflectivity to scintillation light, even if they are not configured to have the first and second light reflectors 47a and 47b, respectively. Because the radiation detector RD2 has a configuration in which the first and second light reflectors 47a and 47b are not placed on the other sides 1d and 1f, the spacing between radiation detectors RD2 in the radiation detector array RA2 is reduced.

[0217] In the radiation detector array RA2, each first semiconductor photodetector element 10a adjacent to each other in the third direction D3 is formed integrally with one another. In this case, when fabricating a radiation detector array RA2 in which multiple radiation detectors RD2 are arranged in a two-dimensional matrix, the process of forming the first semiconductor photodetector element 10a is simplified.

[0218] In the radiation detector array RA2, each second semiconductor photodetector element 10b adjacent to each other in the second direction D2 is formed integrally with one another. In this case, when fabricating a radiation detector array RA2 in which multiple radiation detectors RD2 are arranged in a matrix in a two-dimensional manner, the process of forming the second semiconductor photodetector element 10b is simplified.

[0219] While embodiments and modifications of the present invention have been described above, the present invention is not necessarily limited to the embodiments and modifications described above, and various modifications are possible without departing from the spirit of the invention.

[0220] In radiation detectors RD1 and RD2, the photodetection region 23 does not necessarily have to have a contour shape corresponding to the contour shapes of the sides 1c and 1e when viewed from the second direction D2. In a configuration where the photodetection region 23 has a contour shape corresponding to the contour shapes of the sides 1c and 1e, as described above, the photodetection region 23 does not need to be placed in areas of the semiconductor substrates 11, 11a, and 11b where scintillation light cannot be received, thus suppressing the increase in dark count and capacitance in the photodetection region 23. Therefore, this configuration reliably improves the time resolution of radiation detectors RD1 and RD2. The radiation detectors RD1 and RD2 do not necessarily have substrates 40, 40a, and 40b. In the configuration in which the radiation detectors RD1 and RD2 have substrates 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 semiconductor photodetectors 10, 10a, and 10b with reinforced mechanical strength. The radiation detectors RD1 and RD2 do not necessarily have to be equipped with resin 45. In the configuration in which the radiation detectors RD1 and RD2 are equipped with resin 45, the first and second wires 43 and 44 are protected from damage as described above. Therefore, the radiation detectors RD1 and RD2 reliably realize semiconductor photodetectors 10, 10a and 10b with improved mechanical strength. The radiation detectors RD1 and RD2 do not necessarily have light reflectors 47, 47a, and 47b. In a configuration where radiation detectors RD1 and RD2 are equipped with light reflectors 47, 47a, and 47b, when one radiation detector RD1 or RD2 is positioned alongside the other radiation detectors RD1 or RD2, the light reflectors 47, 47a, and 47b of one radiation detector RD1 or RD2 improve the reflectivity of scintillation light on the other sides 1d and 1f facing the sides of the other radiation detectors RD1 or RD2. Therefore, this configuration simplifies the configuration of the radiation detectors RD1 and RD2. The wiring members 30, 30a, and 30b do not necessarily have to be located on the same side as the scintillator 1 with respect to the semiconductor substrates 11, 11a, and 11b. In a configuration where the wiring members 30, 30a, and 30b are located on the same side as the scintillator 1 with respect to the semiconductor substrates 11, 11a, and 11b, it is not necessary to prepare a new substrate for connecting the wiring members 30, 30a, and 30b to the first and second electrodes 17 and 18 by die bonding, for example. Therefore, this configuration more reliably simplifies the configuration of the radiation detectors RD1 and RD2. The flexibility of the wiring members 30, 30a, and 30b does not need to be greater than the flexibility of the semiconductor substrates 11, 11a, and 11b. In a configuration where the flexibility of the wiring members 30, 30a, and 30b is greater than that of the semiconductor substrates 11, 11a, and 11b, as described above, vibrations are less likely to be transmitted from the wiring members 30, 30a, and 30b to the semiconductor substrates 11, 11a, and 11b. Therefore, this configuration reliably maintains the mechanical strength of the radiation detectors RD1 and RD2. [Explanation of Symbols]

[0221] 1...Scintillator, 1a...End face, 1b...End face, 1c...Side view, 10...Semiconductor photodetector, 10a...First semiconductor photodetector, 10b...Second semiconductor photodetector, 11...Semiconductor substrate, 11a...First semiconductor substrate, 11b...Second semiconductor substrate, 12...Avalanche photodiode, 13...Quenching resistor, 14a...Conducting wire, 14b...Conducting wire, 17...First electrode, 18...Second electrode, 21...First part, 22...Second part, 23...Photodetection region, 3 0...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 part, 52...Fourth part, 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 including the direction in which radiation is incident, and a side surface connecting the pair of end faces, wherein one of the pair of end faces is the surface into which radiation is incident, A semiconductor photodetector having a semiconductor substrate arranged to face the aforementioned side surface, A wiring member electrically connected to the aforementioned semiconductor photodetector, A substrate is arranged such that the semiconductor substrate is positioned between it and one of the scintillators, Equipped with, The length of the scintillator in the first direction is greater than the length of the scintillator in the second direction perpendicular to the side surface. The length of the side surface in the first direction is greater than the width of the side surface in the third direction perpendicular to the first and second directions. The semiconductor substrate has a first portion covered by the side surface and a second portion that, when viewed from the second direction, is aligned with the first portion in the first direction on the other end face side of the pair of end faces and is exposed from the side surface, and the second portion and the one scintillator are aligned in the first direction when viewed from the second direction. The first part comprises a photodetection region having a plurality of avalanche photodiodes operating in Geiger mode and a plurality of quenching resistors electrically connected in series with one of the anodes and cathodes of a corresponding avalanche photodiode, wherein the avalanche photodiodes are arranged in a plurality in the first direction and the third direction, and the number of avalanche photodiodes arranged in the first direction is greater than the number of avalanche photodiodes arranged in the third direction. The second part includes a first electrode to which the plurality of quenching resistors are connected in parallel, and a second electrode to which the other ends of the anodes and cathodes of the plurality of avalanche photodiodes are connected in parallel. The substrate has a third portion covered by the semiconductor substrate, and is arranged such that the semiconductor substrate is located between the third portion and the one scintillator in the second direction. The wiring member is located away from the scintillator in the first direction from one end face to the other end face, and has a conductor electrically connected to the first electrode and a conductor connected to the second electrode, wherein the wiring member is located away from the scintillator in the first direction from one end face to the other end face, and is a radiation detector.

2. The radiation detector according to claim 1, wherein, when viewed from the first direction, one of the scintillators has a rectangular or triangular shape.

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

4. The radiation detector according to claim 1 or 2, wherein, of the pair of end faces, the end face extending in the second direction has a triangular wave shape in its cross-section.

5. The radiation detector according to claim 1 or 2, wherein of the pair of end faces, the end face extending in the second direction is a rough surface.

6. The radiation detector according to any one of claims 1 to 5, wherein the one scintillator has another side surface adjacent to the side surface, which connects the pair of end faces and has a triangular wave cross-section.

7. The radiation detector according to any one of claims 1 to 5, wherein the one scintillator has another rough surface that connects the pair of end faces and is adjacent to the side surface.

8. The radiation detector according to any one of claims 1 to 7, wherein, when viewed from the second direction, the light detection region exhibits a contour shape corresponding to the contour shape of the side surface.

9. The substrate has a fourth portion which is aligned with the third portion in the first direction from one end face toward the other end face and is exposed from the semiconductor substrate, The fourth portion includes a first terminal and a second terminal located on the same side as the one scintillator with respect to the semiconductor substrate, The radiation detector according to any one of claims 1 to 8, 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.

10. The radiation detector according to claim 9, wherein the first wire and the second wire are covered with resin.

11. The radiation detector according to any one of claims 1 to 10, further comprising a light reflector positioned between the semiconductor substrate and the scintillator.

12. The radiation detector according to claim 11, wherein the thickness of the light reflector is 0.05 to 100 μm.

13. The radiation detector according to any one of claims 1 to 12, wherein the wiring member is arranged on the same side as the one scintillator with respect to the semiconductor substrate.

14. The wiring member and the semiconductor substrate are flexible, The radiation detector according to any one of claims 1 to 13, wherein the flexibility of the wiring member is greater than that of the semiconductor substrate.

15. A scintillator having a rectangular shape when viewed from a first direction including the direction in which radiation is incident, and having a pair of end faces that face each other in the first direction, a first side surface connecting the pair of end faces, and a second side surface that connects the pair of end faces and is adjacent to the first side surface, wherein one of the pair of end faces is the surface in which radiation is incident, A first semiconductor photodetector having a first semiconductor substrate arranged to face the first side surface, A second semiconductor photodetector having a second semiconductor substrate arranged to face the second side surface, A first wiring member electrically connected to the first semiconductor photodetector, A second wiring member electrically connected to the second semiconductor photodetector, A first substrate is arranged such that the first semiconductor substrate is positioned between it and one of the scintillators, A second substrate is positioned between the first scintillator and the second semiconductor substrate, Equipped with, The length of one scintillator in the first direction is greater than the length of one scintillator in the second direction perpendicular to the first side surface and the length of one scintillator in the third direction perpendicular to the second side surface. The length of the first side surface in the first direction is greater than the width of the first side surface in the third direction. The length of the second side in the first direction is greater than the width of the second side in the second direction. The first semiconductor substrate and the second semiconductor substrate each have a first portion covered by either the corresponding first side surface or the second side surface, and a second portion aligned with the first portion in the first direction and exposed from either the corresponding first side surface or the second side surface, wherein the second portion of the first semiconductor substrate and the one scintillator are aligned in the first direction when viewed from the second direction, and the second portion of the second semiconductor substrate and the one scintillator are aligned in the first direction when viewed from the third direction. The first portion has a photodetection region having a plurality of avalanche photodiodes operating in Geiger mode and a plurality of quenching resistors electrically connected in series with one of the anodes and cathodes of a corresponding avalanche photodiode, wherein in the photodetection region located in the first portion of the first semiconductor substrate, the avalanche photodiodes are arranged in a plurality in each of the first and third directions, and the number of avalanche photodiodes arranged in the first direction is greater than the number of avalanche photodiodes arranged in the third direction, and in the photodetection region located in the first portion of the second semiconductor substrate, the avalanche photodiodes are arranged in a plurality in each of the first and second directions, and the number of avalanche photodiodes arranged in the first direction is greater than the number of avalanche photodiodes arranged in the second direction. The second part includes a first electrode to which the plurality of quenching resistors are connected in parallel, and a second electrode to which the other ends of the anodes and cathodes of the plurality of avalanche photodiodes are connected in parallel. The first substrate has a third portion covered by the first semiconductor substrate, and is arranged such that the first semiconductor substrate is located between the third portion and the one scintillator in the second direction. The second substrate has a third portion covered by the second semiconductor substrate, and is arranged such that the second semiconductor substrate is positioned between the third portion and the one scintillator in the third direction. The first wiring member and the second wiring member are located away from the scintillator in the first direction from one end face to the other end face, and each has a conductor electrically connected to the first electrode and a conductor connected to the second electrode, respectively, and is a radiation detector.

16. The radiation detector according to claim 15, wherein at least one of the pair of end faces is inclined with respect to the second direction.

17. The radiation detector according to claim 15 or 16, wherein, of the pair of end faces, the end face extending in the second direction has a cross-sectional shape that is triangular wave-shaped.

18. The radiation detector according to claim 15 or 16, wherein at least one of the pair of end faces is a rough surface.

19. Viewed from the second direction, the photodetection region of the first semiconductor substrate has a contour shape corresponding to the contour shape of the first side surface. The radiation detector according to any one of claims 15 to 18, wherein, when viewed from the third direction, the photodetection region of the second semiconductor substrate has a contour shape corresponding to the contour shape of the second side surface.

20. The first substrate and the second substrate each have a fourth portion that is aligned with the third portion in the first direction from one end face to the other end face and is exposed from the first semiconductor substrate and the second semiconductor substrate, respectively. Each of the four parts includes a first terminal and a second terminal that are located on the same side as the one scintillator with respect to the corresponding first semiconductor substrate or the second semiconductor substrate. The radiation detector according to any one of claims 15 to 19, 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.

21. The radiation detector according to claim 20, wherein the first wire and the second wire are covered with resin.

22. A first light reflector is positioned such that the first semiconductor substrate is located between it and one of the scintillators, A radiation detector according to any one of claims 15 to 21, further comprising: a second light reflector disposed such that the second semiconductor substrate is positioned between it and the first scintillator.

23. The radiation detector according to claim 22, wherein the thickness of the first light reflector and the second light reflector is 0.05 to 100 μm.

24. The first wiring member is positioned on the same side as the first scintillator with respect to the first semiconductor substrate. The radiation detector according to any one of claims 15 to 23, wherein the second wiring member is arranged on the same side as the one scintillator with respect to the second semiconductor substrate.

25. The first wiring member and the second wiring member, and the first semiconductor substrate and the second semiconductor substrate are flexible, The flexibility of the first wiring member is greater than that of the first semiconductor substrate. The radiation detector according to any one of claims 15 to 24, wherein the flexibility of the second wiring member is greater than that of the second semiconductor substrate.

26. A radiation detector array in which multiple radiation detectors are arranged in a matrix in a two-dimensional arrangement when viewed from a first direction, Each of the plurality of radiation detectors is the radiation detector described in any one of claims 1 to 14, A radiation detector array in which the semiconductor photodetector elements of one radiation detector are aligned with the semiconductor photodetector elements of another radiation detector adjacent to it in a direction parallel to the side surface.

27. The radiation detector array according to claim 26, wherein each of the semiconductor photodetectors adjacent to each other in a direction parallel to the side surface is integrally formed with respect to each other.

28. A radiation detector array in which multiple radiation detectors are arranged in a matrix in a two-dimensional arrangement when viewed from a first direction, Each of the plurality of radiation detectors is the radiation detector described in any one of claims 15 to 25, The first semiconductor photodetector of one of the radiation detectors is aligned with the first semiconductor photodetector of another radiation detector that is 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 yet another radiation detector that is adjacent in the second direction.

29. The radiation detector array according to claim 28, wherein each of the first semiconductor photodetectors adjacent to each other in the third direction is integrally formed with respect to each other.

30. The radiation detector array according to claim 28 or 29, wherein each of the second semiconductor photodetectors adjacent to each other in the second direction is integrally formed with respect to each other.

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