Radiation detector

Abstract

To provide a technology for guiding more scintillation light, emitted from a scintillator, to a photomultiplier tube.SOLUTION: A radiation detector includes: a scintillator having a flat plate shape extending in a first direction and a second direction intersecting the first direction; a photomultiplier tube configured to detect scintillation light; and a light guide having an opening that is closed by the scintillator, having a box shape with a reflective inner surface, and configured to guide the scintillation light, emitted from the scintillator, to the photomultiplier tube. The inner surface includes: a first reflecting surface from which a light-receiving surface of the photomultiplier tube is exposed; and a second reflecting surface provided on a scintillator side along a third direction with respect to the first reflecting surface, extending along the second direction, and inclining to a first side as viewed from the scintillator side. The light guide includes a reflecting member provided on the scintillator side along the third direction with respect to the first reflecting surface, inclining to the first side as viewed from the scintillator side, and having reflecting surfaces on both sides thereof.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present disclosure relates to radiation detectors. [Background technology]

[0002] Patent Document 1 discloses a scintillation detector including a case with an open top and a reflective inner surface, a scintillator plate arranged to cover the top of the case, and a photomultiplier tube arranged horizontally inside the case. Patent Document 1 discloses that the scintillation detector further includes a light path changing means for guiding more of the scintillation light that is emitted from the scintillator plate on the top of the cover and cannot directly reach the light receiving surface of the photomultiplier tube to the light receiving surface of the photomultiplier tube. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2002-006048 A Summary of the Invention [Problem to be solved by the invention]

[0004] In a radiation detector including a scintillator and a photomultiplier tube, it is required that the photomultiplier tube detects as much of the scintillation light emitted from the scintillator as possible.

[0005] The present disclosure provides a radiation detector that directs more of the scintillation light emitted from the scintillator to a photomultiplier tube. [Means for solving the problem]

[0006] According to one aspect of the present disclosure, there is provided a light guide including a scintillator having a flat plate shape extending in a first direction and a second direction intersecting the first direction, the scintillator absorbing radiation and converting it into scintillation light, a photomultiplier tube detecting the scintillation light, and a light guide having a box shape with an inner surface being a reflective surface, the light guide having an opening that is open in a third direction intersecting the first direction and the second direction and is closed by the scintillator, the light guide guiding the scintillation light emitted from the scintillator to the photomultiplier tube, the inner surface being spaced apart from the scintillator, extending in the second direction and the third direction, facing a first side along the first direction, and a light guide having a light guide portion that is spaced apart from the scintillator, the light guide portion being spaced apart from the photomultiplier tube, the light guide portion being ... the light guide is a plate-like member extending along the second direction, is on the first side of the first reflecting surface, is on the scintillator side of the first reflecting surface along the third direction from the first reflecting surface, extends along the second direction and is inclined toward the first side as viewed from the scintillator side, and the light guide is a plate-like member extending along the second direction, is on the first side of the first reflecting surface, is on the scintillator side of the first reflecting surface along the third direction from the first reflecting surface, is inclined toward the first side as viewed from the scintillator side, and comprises a reflective member having reflective surfaces on both sides. Effect of the Invention

[0007] According to the radiation detector of the present disclosure, it is possible to guide a larger amount of scintillation light emitted from the scintillator to the photomultiplier tube. [Brief description of the drawings]

[0008] [Figure 1] FIG. 1 is a perspective view of a body surface monitor in which a radiation detector according to this embodiment is used. [Diagram 2] FIG. 2 is a perspective view of the radiation detector according to the present embodiment. [Diagram 3] FIG. 3 is an exploded perspective view of the radiation detector according to the present embodiment. [Figure 4] FIG. 4 is a rear view of the radiation detector according to the present embodiment. [Diagram 5] FIG. 5 is a rear view of the radiation detector according to this embodiment. [Figure 6] FIG. 6 is a side view of the radiation detector according to the present embodiment. [Figure 7] FIG. 7 is a front view of the light guide in the radiation detector according to this embodiment. [Figure 8] FIG. 8 is a perspective view of a light guide in the radiation detector according to this embodiment. [Figure 9] FIG. 9 is a cross-sectional view of a light guide in the radiation detector according to this embodiment. [Figure 10] FIG. 10 is an exploded perspective view of a radiation detector according to a reference example. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] Hereinafter, embodiments will be described with reference to the accompanying drawings. Note that the present disclosure is not limited to these examples, but is defined by the claims, and is intended to include all modifications within the meaning and scope of the claims.

[0010] In addition, in the description of the specification and drawings of each embodiment, components having substantially the same or corresponding functional configurations may be denoted by the same reference numerals to avoid redundant explanations. In addition, in order to facilitate understanding, the scale of each part in the drawings may differ from the actual scale.

[0011] In the directions of parallel, right-angle, orthogonal, horizontal, vertical, up-down, left-right, front-back, etc., deviations are permitted to the extent that they do not impair the effects of the embodiment. The shape of the corners is not limited to right angles and may be rounded. Parallel, right-angle, orthogonal, horizontal, and vertical may include approximately parallel, approximately right-angle, approximately orthogonal, approximately horizontal, and approximately vertical, respectively.

[0012] For example, "approximately parallel" means that even if two lines or two surfaces are not completely parallel to each other, they can be treated as parallel to each other as long as it is within the range of manufacturing tolerance. As with "approximately parallel," "approximately right angle," "approximately perpendicular," "approximately horizontal," and "approximately vertical" are also intended to correspond to the respective terms as long as the relative positional relationship between the two lines or two surfaces is within the range of manufacturing tolerance.

[0013] <Body surface monitor> A body surface monitor using a radiation detector according to this embodiment will be described below. Fig. 1 is a perspective view of a body surface monitor 100, which is an example of a body surface monitor using a radiation detector according to this embodiment.

[0014] The body surface monitor 100 measures radioactive substances and the like attached to the body of a worker. The body surface monitor 100 is a device that measures surface contamination of the body of a worker by radioactive substances and the like. The body surface monitor 100 includes a front measuring unit 110, a rear measuring unit 120, a left measuring unit 130, a right measuring unit 140, a lower measuring unit 150, and an upper connecting unit 160.

[0015] The front measuring unit 110 measures surface contamination on the abdomen side of the worker's body. The front measuring unit 110 also has a hand measuring unit on the side where the worker's hand is inserted. The front measuring unit 110 has a total of seven radiation detectors 1 according to the present embodiment described later, which are body radiation detectors, lined up in the vertical direction. The front measuring unit 110 also has a total of two hand radiation detectors on the left and right sides. Furthermore, the front measuring unit 110 has one head radiation detector on the upper side that measures surface contamination on the worker's head. The head radiation detector moves in the vertical direction according to the worker's height. The head radiation detector is the same detector as the foot radiation detector described later.

[0016] The rear measuring unit 120 measures surface contamination on the back side of the body of the worker. The rear measuring unit 120 includes a total of seven radiation detectors 1 according to this embodiment, which will be described later and are body radiation detectors, lined up in the vertical direction.

[0017] The left measuring unit 130 and the right measuring unit 140 each measure surface contamination on the side of the worker's body. The left measuring unit 130 and the right measuring unit 140 are each attached between the front measuring unit 110 and the rear measuring unit 120 so as to be able to open and close. Specifically, the left measuring unit 130 and the right measuring unit 140 are each attached to the rear measuring unit 120 so as to be able to rotate. The left measuring unit 130 and the right measuring unit 140 each function as a door. The left measuring unit 130 and the right measuring unit 140 each include a total of six radiation detectors 1 which are body radiation detectors.

[0018] The lower measuring unit 150 measures surface contamination on the feet of a worker. The lower measuring unit 150 includes a total of two foot radiation detectors arranged in the left-right direction.

[0019] The upper connection part 160 connects and fixes the front measurement part 110 and the rear measurement part 120 at their upper sides.

[0020] The body surface monitor 100 is equipped with 31 radiation detectors in total, including 26 body radiation detectors, two hand radiation detectors, two foot radiation detectors, and one head radiation detector. Because the body surface monitor 100 is equipped with many body radiation detectors, there is a demand for improved detection performance, especially for the body radiation detectors. In addition, because the body surface monitor 100 is equipped with many body radiation detectors, there is a demand for reduced cost, especially for the body radiation detectors.

[0021] <Radiation detector> Next, the radiation detector according to this embodiment will be described. The radiation detector according to this embodiment is, for example, a body radiation detector used in the above-mentioned body surface monitor 100. The radiation detector according to this embodiment is flat and extends in a first direction and a second direction intersecting the first direction, and includes a scintillator that absorbs radiation and converts it into scintillation light, and a photomultiplier tube that detects the scintillation light. The radiation detector according to this embodiment also includes a light guide that guides the scintillation light emitted from the scintillator to the photomultiplier tube. The light guide included in the radiation detector according to this embodiment is box-shaped, having an opening that opens in a third direction intersecting the first and second directions and is blocked by the scintillator, and the inner surface is a reflective surface.

[0022] The inner surface of the light guide in the radiation detector according to this embodiment has a first reflecting surface that is provided at a distance from the scintillator, extends in the second and third directions, faces the first side along the first direction, and partially exposes the light receiving surface of the photomultiplier tube. The inner surface of the light guide in the radiation detector according to this embodiment has a second reflecting surface that is on the second side opposite to the first side from the first reflecting surface along the first direction, and is provided on the scintillator side from the first reflecting surface along the third direction and extends along the second direction. The second reflecting surface of the inner surface of the light guide in the radiation detector according to this embodiment is inclined toward the first side when viewed from the scintillator side.

[0023] Moreover, the light guide in the radiation detector according to this embodiment is a plate-like member extending along the second direction, and includes a reflecting member provided on the first side with respect to the first reflecting surface and on the scintillator side from the first reflecting surface along the third direction. The reflecting member included in the light guide in the radiation detector according to this embodiment is inclined toward the first side when viewed from the scintillator side, and both sides are reflective surfaces.

[0024] The radiation detector according to this embodiment will be described with reference to the drawings. Fig. 2 is a perspective view of the radiation detector 1, which is an example of the radiation detector according to this embodiment. Fig. 3 is an exploded perspective view of the radiation detector 1, which is an example of the radiation detector according to this embodiment. Figs. 4 and 5 are each a rear view of the radiation detector 1, which is an example of the radiation detector according to this embodiment. Fig. 6 is a side view of the radiation detector 1, which is an example of the radiation detector according to this embodiment.

[0025] For ease of explanation, the drawings may have a virtual three-dimensional coordinate system (XYZ Cartesian coordinate system) consisting of mutually orthogonal X-axis, Y-axis, and Z-axis (XYZ axes) set. For a coordinate axis perpendicular to the paper surface of the drawing, a black circle in the circle of the coordinate axis indicates that the axis faces the front side of the paper surface. A cross in the circle of the coordinate axis indicates that the axis faces the back side of the paper surface.

[0026] However, this coordinate system is defined for the purpose of explanation and does not limit the orientation of the radiation detector according to this embodiment.

[0027] In the following drawings, the X-axis direction and the Y-axis direction are the directions in which the scintillator 20 extends, and the Z-axis direction is the direction perpendicular to the X-axis direction and the Y-axis direction.

[0028] The radiation detector 1, which is an example of a radiation detector according to this embodiment, includes a front frame 10, a scintillator 20, a light guide 30, a box 40, a photomultiplier tube 50, and a circuit board 60.

[0029] [Front frame 10] The front frame 10 functions as a protective plate that protects the surface of the radiation detector 1. In addition, the front frame 10 prevents light from entering the inside of the light guide 30. The front frame 10 includes a light-shielding film for blocking light.

[0030] The front frame 10 is attached to the front surface of the light guide 30 by, for example, screwing.

[0031] [Scintillator 20] The scintillator 20 absorbs radiation and converts it into scintillator light. The scintillator 20 is made of, for example, plastic. That is, the scintillator 20 is a plastic scintillator.

[0032] The scintillator 20 has a flat plate shape extending in the X-axis direction and the Y-axis direction. The scintillator 20 is sandwiched between the front frame 10 and the light guide 30. The light guide 30 has a recess at an opening 30h in order to accommodate the scintillator 20. The scintillator 20 is accommodated in the recess.

[0033] [Light Guide 30] The light guide 30 absorbs radiation in the scintillator 20 and guides the emitted scintillator light to the photomultiplier tube 50 .

[0034] The light guide 30 has a box-like shape having an opening 30h that opens to the +Z side in the Z-axis direction. The opening 30h is closed by the scintillator 20. An inner surface 30i of the light guide 30 is a reflective surface that reflects the scintillation light. By reflecting the scintillation light by the inner surface 30i of the light guide 30, the light guide 30 guides the scintillation light emitted from the scintillator 20 to a photomultiplier tube 50 attached to the light guide 30.

[0035] The light guide 30 includes a plurality of ribs 31. The ribs 31 include screw holes on both sides in the Z-axis direction for mounting the front frame 10 and for mounting the radiation detector 1 to the body surface monitor 100. The ribs 31 are fitted with screws for mounting the front frame 10 and screws for mounting the radiation detector 1 to a device such as the body surface monitor 100. The direction in which the radiation detector 1 is mounted can be selected between the X-axis direction and the Y-axis direction depending on the mounting position of the ribs 31.

[0036] The light guide 30 is formed of, for example, resin. An insert nut may be press-fitted into the rib 31 of the light guide 30 along the Z-axis direction. The shape of the light guide 30 is preferably structured so that the mold can be removed in the Z-axis direction. By having the structure so that the mold can be removed in the Z-axis direction, for example, a slide mechanism is not required in the mold, and therefore the cost of the mold can be reduced.

[0037] The thickness of the light guide 30 is, for example, not less than 60 mm and not more than 100 mm.

[0038] [Box 40] The box 40 fixes the photomultiplier tube 50 and the circuit board 60 to the light guide 30. The box 40 houses the photomultiplier tube 50 and the circuit board 60 inside.

[0039] FIG. 4 is a rear view of the radiation detector 1. FIG. 5 is a rear view of the radiation detector 1 with the covers 41 and 42 of the box 40 removed. The box 40 is made of metal. The box 40 houses the photomultiplier tube 50 and the circuit board 60 inside. The box 40 is made of a conductive material such as metal, thereby suppressing the effects of noise and the like. The box 40 includes a partition made of a conductive material between the photomultiplier tube 50 and the circuit board 60. The box 40 includes a partition, which can reduce noise from the circuit board 60 to the photomultiplier tube 50. The box 40 includes a partition, which can prevent light from entering the photomultiplier tube 50 from the circuit board 60 side.

[0040] The box 40 is attached to the light guide 30 by, for example, screwing. By attaching the box 40 to the light guide 30 by screwing, the number of steps required for assembly can be reduced.

[0041] The box 40 includes a cover 41 and a cover 42. By removing the cover 41 and the cover 42, respectively, the photomultiplier tube 50 and the circuit board 60 can be checked and worked on, respectively. For example, when a shipping inspection is performed on the radiation detector 1, the cover 42 is removed. When the shipping inspection is performed with the cover 42 removed, the photomultiplier tube 50 is shielded from light by the cover 41 and the partition of the box 40, so that it is possible to prevent light from entering the photomultiplier tube 50 and causing erroneous counting during the shipping inspection.

[0042] [Photomultiplier Tube 50] The photomultiplier tube 50 converts the scintillation light into electrons and amplifies them. A high voltage (e.g., 1000 volts) is supplied to the photomultiplier tube 50 from the circuit board 60. The photomultiplier tube 50 uses the high voltage supplied from the circuit board 60 to amplify the electrons.

[0043] [Circuit board 60] The circuit board 60 supplies a high voltage to the photomultiplier tube 50. In addition, the circuit board 60 amplifies the electrical signal output from the photomultiplier tube 50.

[0044] The terminals 61, 62, and 63 of the circuit board 60 are exposed on the -X side in the X-axis direction. The box 40 has an opening 40h through which the terminals 61, 62, and 63 are exposed on the -X side in the X-axis direction.

[0045] <Inner surface shape of light guide> The shape of the inner surface 30i of the light guide 30 will be described. Fig. 7 is a front view of the light guide 30 in the radiation detector 1, which is an example of the radiation detector according to this embodiment. Fig. 8 is a perspective view of the light guide 30 in the radiation detector 1, which is an example of the radiation detector according to this embodiment. Fig. 9 is a cross-sectional view of the light guide 30 in the radiation detector 1, which is an example of the radiation detector according to this embodiment.

[0046] The inner surface 30i of the light guide 30 is formed by combining a plurality of reflecting surfaces. The inner surface 30i includes reflecting surfaces 30i1, 30i2, 30i3, 30i4, 30i5, 30i6, and 30i7. Each of the reflecting surfaces 30i1, 30i2, 30i3, 30i4, 30i5, 30i6, and 30i7 is formed by a reflecting member such as a mirror. Each of the reflecting surfaces 30i1, 30i2, 30i3, 30i4, 30i5, 30i6, and 30i7 may be an individual reflecting member or may be an integrally formed reflecting member.

[0047] [Reflective surface 30i1] The reflecting surface 30i1 is provided at a distance from the scintillator 20. The reflecting surface 30i1 extends in the Y-axis direction and the Z-axis direction. The reflecting surface 30i1 faces the -X side along the X-axis direction. A light receiving surface 51 of the photomultiplier tube 50 is exposed in a part of the reflecting surface 30i1. The light guide 30 has an opening 30j through which the light receiving surface 51 of the photomultiplier tube 50 is exposed.

[0048] [Reflective surface 30i2] The reflecting surface 30i2 is provided on the +X side, which is the side opposite to the -X side, of the reflecting surface 30i1 along the X-axis direction. The reflecting surface 30i2 is provided on the scintillator 20 side of the reflecting surface 30i1 along the Z-axis direction.

[0049] The reflecting surface 30i2 extends in the Y-axis direction. The reflecting surface 30i2 is inclined toward the -X side when viewed from the scintillator side. The inclination angle θ1 of the reflecting surface 30i2 with respect to the X-axis direction may be appropriately determined within a range of, for example, 5 degrees or more and 50 degrees or less. For example, the inclination angle θ1 is preferably set to 9 degrees or more and 11 degrees or less, for example, 10 degrees.

[0050] The inventors found through simulations that by setting the inclination angle θ1 to be equal to or greater than 9 degrees and equal to or less than 11 degrees, for example, 10 degrees, a larger amount of scintillation light from the end of the scintillator 20 can be reflected toward the reflecting member 32.

[0051] The scintillation light emitted from the +X side of the scintillator 20 is reflected by the reflecting surface 30i2. The scintillation light reflected by the reflecting surface 30i2 is reflected by the reflecting surface 32i2 of the reflecting member 32, which will be described later. The scintillation light reflected by the reflecting surface 32i2 of the reflecting member 32 is incident on the light-receiving surface 51 of the photomultiplier tube 50.

[0052] As described above, the scintillation light emitted from the scintillator 20 is reflected by the reflecting surfaces 30i2 and 32i2 and enters the photomultiplier tube 50, thereby allowing the light guide 30 to guide a larger amount of scintillation light to the photomultiplier tube 50.

[0053] [Reflective surface 30i3] The reflecting surface 30i3 is provided on the -X side of the reflecting surface 30i1 along the X-axis direction. The reflecting surface 30i3 is provided so as to face the reflecting surfaces 30i1 and 30i2.

[0054] The reflecting surface 30i3 extends in the Y-axis direction. The reflecting surface 30i3 is inclined toward the +X side when viewed from the scintillator 20 side. The inclination angle θ2 of the reflecting surface 30i3 with respect to the X-axis direction may be appropriately determined, for example, in the range of 10 degrees or more and 50 degrees or less. Moreover, the inclination angle θ2 is preferably set to 20 degrees or more and 22 degrees or less, for example, 21 degrees. The inclination angle θ1 may be set to be different from the inclination angle θ2.

[0055] [Reflective surface 30i4] The reflecting surface 30i4 extends in the X-axis direction. The reflecting surface 30i4 is inclined toward the -Y side when viewed from the side of the scintillator 20. In other words, the reflecting surface 30i4 is inclined toward the center of the inner surface 30i.

[0056] [Reflective surface 30i5] The reflecting surface 30i5 extends in the X-axis direction. The reflecting surface 30i5 is inclined toward the +Y side when viewed from the side of the scintillator 20. In other words, the reflecting surface 30i5 is inclined toward the center of the inner surface 30i.

[0057] [Reflective surface 30i6] The reflecting surface 30i6 extends in the X-axis direction and the Y-axis direction. The reflecting surface 30i6 is provided between the reflecting surface 30i1 and the reflecting surface 30i2.

[0058] [Reflective surface 30i7] The reflecting surface 30i7 extends in the X-axis direction and the Y-axis direction. The reflecting surface 30i7 is provided between the reflecting surface 30i1 and the reflecting surface 30i3.

[0059] Furthermore, the light guide 30 includes a reflecting member 32. The reflecting member 32 has a plate-like shape extending along the Y-axis direction. The reflecting member 32 is provided on the -X side with respect to the reflecting surface 30i1. The reflecting member 32 is also provided on the scintillator 20 side along the Z-axis direction with respect to the reflecting surface 30i1. Both sides of the reflecting member 32 are reflecting surfaces. That is, the reflecting member 32 has a reflecting surface 32i1 and a reflecting surface 32i2.

[0060] The reflecting member 32 is inclined toward the -X side when viewed from the scintillator 20. The inclination angle θ3 between the scintillator 20 (X-axis direction) and the reflecting surface 32i1 may be, for example, 40 degrees or more and 65 degrees or less, for example, 45 degrees or 60 degrees. Moreover, the inclination angle θ3 is, for example, 51 degrees or more and 53 degrees or less, for example, more preferably 52 degrees.

[0061] Considering the scintillation light from the portion of the scintillator 20 directly above the reflecting member 32, it is desirable that the reflecting member 32 be small when viewed from the scintillator 20 so as not to block the scintillation light. On the other hand, considering the scintillation light reflected by the reflecting surface 30i2, it is desirable that the reflecting member 32 be large when viewed from the reflecting surface 30i2 side (+X side) so as to reflect the scintillation light.

[0062] The inventors found through simulations that by setting the inclination angle θ3 to be greater than or equal to 51 degrees and less than or equal to 53 degrees, for example, 52 degrees, it is possible to reflect scintillation light from the edge of the scintillator 20 while minimizing the blocking of scintillation light from directly above.

[0063] The width of the reflective member 32 is, for example, 20 mm to 30 mm. The reflective member 32 may be shifted, for example, from the center of the scintillator 20 to the +X side by 10 mm to 20 mm, for example, 15 mm.

[0064] <Light collection characteristics of radiation detector 1> For example, in a radiation detector used as a surface monitor for an article, the ratio of the minimum value to the maximum value of the instrument efficiency as a function of the radiation source position is required to be 0.5 or more (for example, Japanese Industrial Standard JIS Z 4337, etc.). A simulation was performed to evaluate the instrument efficiency according to the radiation source position in the radiation detector 1.

[0065] The simulation was performed using ray tracing software. The evaluation was based on the intensity of the light emitted from the light source and reaching the photocathode (light receiving surface). The simulation was performed with a light receiving surface diameter of 38 mm, a light source diameter of 25 mm, 1 million light rays, a reflectance of 0.8 on the reflecting surface, and up to 5 reflections.

[0066] The location of the light source was compared between two locations: the center of the scintillator 20 viewed from the Z-axis direction, which has the greatest influence (first position, maximum intensity), and the end on the +X side, which is the central part in the Y-axis direction (second position, minimum intensity). The in-plane distribution (instrument efficiency depending on the radiation source position) was evaluated by determining the intensity ratio with the light source disposed at the first position and the second position.

[0067] As a result of evaluating the radiation detector 1, the intensity ratio was about 0.60, which was above the target value of 0.5 and was therefore favorable.

[0068] <Summary> According to the radiation detector of this embodiment, it is possible to guide more of the scintillation light emitted from the scintillator to the photomultiplier tube. For example, the radiation detector 1, which is an example of the radiation detector of this embodiment, includes a reflecting surface 30i2 and a reflecting member 32. The radiation detector 1 reflects light emitted from the end of the scintillator 20 on the +X side at the reflecting surface 30i2 and the reflecting member 32 and detects it with the photomultiplier tube 50, so that more scintillation light can be detected by the photomultiplier tube 50. In other words, according to the light guide included in the radiation detector of this embodiment, it is possible to guide more of the scintillation light emitted from the scintillator to the photomultiplier tube.

[0069] Furthermore, in the radiation detector according to this embodiment, the light receiving surface of the photomultiplier tube faces along the X-axis direction, so that, for example, even if the length of the photomultiplier tube increases, the thickness in the depth direction (Z-axis direction) can be reduced.

[0070] In order to explain the effect of the radiation detector according to this embodiment, a radiation detector 300 will be described as a reference example of the radiation detector. Fig. 10 is an exploded perspective view of the radiation detector 300, which is an example of the radiation detector of the reference example.

[0071] The radiation detector 300 includes three light-shielding films 307 that prevent intrusion of light from the outside. The radiation detector 300 includes one light-shielding film 307 on a light-shielding film frame 306. The radiation detector 300 also includes two light-shielding film frames 306 attached to the scintillator 305.

[0072] The scintillator 305 emits light when irradiated with radiation. The light emitted by the scintillator 305 is collected into the photomultiplier tube 302 by the light guide 301 to which a mirror 308 is attached. The photomultiplier tube 302 converts the light into electrons and amplifies them. The electrical signal amplified by the photomultiplier tube 302 is input to the amplifier power supply board 303.

[0073] High-voltage power (about 1000 volts) is supplied to the photomultiplier tube 302. The amplifier power supply board 303 generates high-voltage power (1000 volts) and supplies it to the photomultiplier tube 302.

[0074] In the radiation detector 300, the periphery of the light guide 301 is covered with a case 310. In addition, in the radiation detector 300, the light guide 301 and the case 310 are fixed by two fixing plates 312. In the radiation detector 300, the light shielding film frame 306 and the case 310 are fixed by screws. In the radiation detector 300, four insulating blocks 313 are attached to the case 310, and further, the radiation detector 300 is attached to an apparatus or the like using mounting brackets. In addition, the scintillator 305 is taped in a state where the light guide 301 is placed on the light guide 301 and held down by a holding frame 311.

[0075] The radiation detector 300 includes a cover 315 for blocking light from the photomultiplier tube 302. The radiation detector 300 also includes an amplifier mounting plate 316 for fixing the amplifier power supply board 303 to the light guide 301. The radiation detector 300 further includes a cover 317 for covering the cover 315 and the amplifier power supply board 303.

[0076] For example, taking the radiation detector 300 as an example, if the length of the photomultiplier tube 302 in the radiation detector 300 increases, the thickness of the radiation detector 300 will increase accordingly. For example, in the body surface monitor 100, if the body radiation detector becomes thick, it may not be possible to attach it to the body surface monitor 100.

[0077] In the radiation detector of this embodiment, the photomultiplier tube is oriented in the direction in which the scintillator extends, so that even if the photomultiplier tube is longer, the thickness of the radiation detector can be reduced without increasing its thickness.

[0078] For example, when comparing the radiation detector 1, which is an example of the radiation detector according to this embodiment, with the radiation detector 300 of the reference example, the thickness of the radiation detector 300 is 103 millimeters, while the thickness of the radiation detector 1 is 79 millimeters. In other words, the radiation detector according to this embodiment can be made smaller in size.

[0079] Furthermore, the radiation detector according to this embodiment includes a box for housing the photomultiplier tube and the circuit board, so the photomultiplier tube and the circuit board can be installed in close proximity. Because the photomultiplier tube and the circuit board can be installed in close proximity, the radiation detector according to this embodiment can reduce noise in the photomultiplier tube. Furthermore, by housing the photomultiplier tube and the circuit board in a box, the number of parts for fixing the photomultiplier tube and the circuit board to the light guide can be reduced.

[0080] For example, taking the radiation detector 300 as an example, the radiation detector 300 includes a cover 315 , an amplifier mounting plate 316 and a cover 317 for fixing the photomultiplier tube 302 and the amplifier power supply board 303 to the light guide 301 .

[0081] According to the radiation detector of this embodiment, the box in which the photomultiplier tube and the circuit board are stored allows the photomultiplier tube and the circuit board to be fixed to the light guide with a smaller number of parts than, for example, the radiation detector 300 of the reference example.

[0082] Furthermore, according to the radiation detector of this embodiment, the box has an opening through which the terminal provided on the circuit board is exposed, thereby reducing the stress on the cable connected to the terminal. The radiation detector of this embodiment has an opening through which the terminal provided on the circuit board is exposed, thereby allowing the cable connected to the terminal to be wired on the back side of the light guide. The radiation detector of this embodiment utilizes the space on the back side of the light guide to wire the cable connected to the terminal to the back side of the light guide, thereby allowing the cable to be wired while increasing the bending radius. The radiation detector of this embodiment wires the cable while increasing the bending radius, thereby reducing the stress on the cable.

[0083] Furthermore, according to the radiation detector of this embodiment, the end of the light guide is provided with a threaded rib, which makes it easy to attach the radiation detector to a device, for example, a body surface monitor.

[0084] For example, in the case of the radiation detector 300, when the radiation detector 300 is mounted on a device, four insulating blocks 313 are attached to the case 310, and further mounting brackets are required.

[0085] The radiation detector according to this embodiment can be easily attached to an apparatus without using an insulating block as in the radiation detector 300 of the reference example.

[0086] For example, when comparing the radiation detector 1, which is an example of the radiation detector according to this embodiment, with the radiation detector 300 of the reference example, the number of parts can be reduced from 22 for the radiation detector 300 to 12 for the radiation detector 1. Reducing the number of parts can reduce the amount of direct materials and assembly work. Furthermore, reducing the number of parts can reduce the weight of the radiation detector 1 to 1.5 kilograms compared to 2.5 kilograms for the radiation detector 300. In particular, for example, when the radiation detector is used in a body surface monitor, the weight of the entire device can be reduced by 26 kilograms since 26 units are used in the device.

[0087] The X-axis direction is an example of a first direction, the Y-axis direction is an example of a second direction, the Z-axis direction is an example of a third direction, the -X side is an example of a first side, and the +X side is an example of a second side. Also, the reflecting surface 30i1 is an example of a first reflecting surface, the reflecting surface 30i2 is an example of a second reflecting surface, the reflecting surface 30i3 is an example of a third reflecting surface, and the reflecting surface 30i4 or the reflecting surface 30i5 is an example of a fourth reflecting surface. The inclination angle θ1 is an example of a first inclination angle, the inclination angle θ2 is an example of a second inclination angle, and the inclination angle θ3 is an example of a third inclination angle. [Explanation of symbols]

[0088] 1. Radiation detector 10 Front Frame 20 Scintillator 30 Light Guide 30h opening 30i Inside 30i1, 30i2, 30i3, 30i4, 30i5, 30i6, 30i7 reflective surface 31 Ribs 32 Reflective material 32i1, 32i2 reflective surface 40 Box 40h opening 50 Photomultiplier tube 51 Photosensitive surface 60 Circuit Board Terminals 61, 62, 63 100 Body Surface Monitor θ1, θ2, θ3 Tilt angle

Claims

1. a scintillator having a flat plate shape extending in a first direction and a second direction intersecting the first direction, the scintillator absorbing radiation and converting it into scintillation light; a photomultiplier tube for detecting the scintillation light; a light guide having a box-like shape, the light guide having an opening that is open in a third direction intersecting the first direction and the second direction and is closed by the scintillator, the inner surface of the light guide being a reflective surface, the light guide guiding the scintillation light emitted from the scintillator to the photomultiplier tube; Equipped with The inner surface is a first reflecting surface that is provided at a distance from the scintillator, extends in the second direction and the third direction, faces a first side along the first direction, and has a light receiving surface of the photomultiplier tube exposed at a part of the first reflecting surface; a second reflection surface that is provided on a second side that is a side opposite to the first side from the first reflection surface along the first direction, on the scintillator side from the first reflection surface along the third direction, extends along the second direction, and is inclined toward the first side as viewed from the scintillator side; having the light guide is a plate-like member extending along the second direction, is provided on the first side of the first reflecting surface, is closer to the scintillator along the third direction than the first reflecting surface, is inclined toward the first side as viewed from the scintillator side, and includes a reflecting member having reflecting surfaces on both sides. Radiation detector.

2. a first inclination angle, which is an inclination angle of the second reflecting surface with respect to the first direction, is equal to or greater than 9 degrees and equal to or less than 11 degrees; The radiation detector according to claim 1 .

3. the inner surface further includes a third reflecting surface that is provided on the first side of the first reflecting surface in the first direction, extends along the second direction, and is inclined toward the second side as viewed from the scintillator; The radiation detector according to claim 1 .

4. a second inclination angle, which is an inclination angle of the third reflecting surface with respect to the first direction, is equal to or greater than 20 degrees and is equal to or less than 22 degrees; The radiation detector according to claim 3 .

5. a first tilt angle that is a tilt angle of the second reflecting surface with respect to the first direction is different from a second tilt angle that is a tilt angle of the third reflecting surface with respect to the first direction; The radiation detector according to claim 3 .

6. a third inclination angle which is an inclination angle of the reflecting member with respect to the first direction is equal to or greater than 51 degrees and equal to or less than 53 degrees; The radiation detector according to claim 1 .

7. a fourth reflecting surface provided at an end of the inner surface in the second direction, extending along the first direction, and inclined toward a center of the inner surface; The radiation detector according to any one of claims 1 to 6.

8. a box for accommodating the photomultiplier tube and a circuit board on the rear side of the first reflecting surface of the light guide; The radiation detector according to any one of claims 1 to 6.

9. the box has an opening on the first side through which a terminal provided on the circuit board is exposed; The radiation detector according to claim 8.

10. The light guide includes a threaded rib at a rear end in at least one of the first direction and the second direction. The radiation detector according to any one of claims 1 to 6.

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