Radiation source installation tool and radioactivity measurement device

Abstract

To provide a radiation source installation tool and a radioactivity measurement device capable of easily obtaining a measurement result equivalent to desired measurement to a radiation source.SOLUTION: A radiation source installation tool 10 includes a support part 11 and a plurality of different distance changing parts 13. The support part 11 has a cylindrical outer shape. The support part 11 includes a first end 11a and a second end 11b at both ends in the axial direction along the central axis. The first end 11a is provided with an inner circumferential part that is radially enlarged by one step so as to be mounted on the front end of an end cap housing 3a of the radiation detector 3 along the axial direction by fitting. The second end 11b is provided with an inner circumferential part that is radially enlarged by one step, so that the distance-changing part 13 is mounted along the axial direction by fitting. The plurality of different distance-changing parts 13 include a first distance-changing part 13A (13) and a second distance-changing part 13B (13) having different lengths in the axial direction along the central axis.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a radiation source installation jig and a radioactivity measuring device. [Background technology]

[0002] BACKGROUND ART Conventionally, a jig is known that positions and fixes a radiation source such as a standard radiation source at a predetermined position relative to a radiation detector when measuring the relative efficiency of the radiation detector (see, for example, Non-Patent Document 1). [Prior art documents] [Non-patent literature]

[0003] [Non-Patent Document 1] "Radioactivity Measurement Method Series 7: Gamma-ray Spectrometry Using Germanium Semiconductor Detectors," Nuclear Regulation Authority, 2020, p.178 Summary of the Invention [Problem to be solved by the invention]

[0004] Incidentally, when performing measurements with a low background for the radiation source, it is necessary to arrange the radiation source, the jig, the head of the radiation detector, etc. inside the shielding. However, for example, when the radiation detector is replaced while the combination of the radiation detector and the shielding is optimized, it may be impossible to attach the predetermined jig to the radiation detector inside the shielding. For example, if it is impossible to position the radiation source at a predetermined position inside the shielding using the predetermined jig, or if it is necessary to move the radiation detector relative to the shielding to attach the predetermined jig, it may be difficult to reliably perform desired measurements such as relative efficiency.

[0005] An object of the present invention is to provide a radiation source installation jig and a radioactivity measuring device that can easily obtain measurement results equivalent to desired measurements of a radiation source. [Means for solving the problem]

[0006] In order to solve the above problems and achieve the above object, the present invention employs the following aspects. (1): A radiation source installation jig (10, 20, 30, 40, 50) according to one aspect of the present invention is a radiation source installation jig that positions and fixes a radiation source (S), and includes a distance change unit (13, 21, 23, 33, 35, 43, 45, 53) that changes the distance between the radiation source and a predetermined position (3A).

[0007] (2): The radiation source installation jig described in (1) above includes a radiation source holding portion (13a, 25a, 37a, 47a, 53a) that holds the radiation source and has a through hole that penetrates toward the predetermined position, and the shape of the distance change portion may be such that it does not interfere with the through hole and the predetermined position.

[0008] (3): The radiation source installation jig described in (1) above may include a display unit (55) that displays information about the distance between the radiation source and the predetermined position, and the distance change unit (53) may include a moving unit (53) that moves between the radiation source and the predetermined position, and guide units (51b, 53c) that guide the movement of the moving unit.

[0009] (4) The radiation source installation jig according to any one of (1) to (3) above may include a support portion (11, 31, 41, 51) that supports the distance changer by fitting.

[0010] (5): A radioactivity measuring device (1) according to one embodiment of the present invention includes a radiation source installation jig (10, 20, 30, 40, 50) according to any one of (1) to (3) above, a shielding body (9), and a radiation detector (3) to which the radiation source installation jig is attached inside the shielding body.

[0011] (6): The radioactivity measuring device according to (5) above is configured to calculate a first relative efficiency (relative efficiency E h) based on the second relative efficiency (relative efficiency E H ) may be provided.

[0012] (7): In the radioactivity measuring device described in (6) above, the processing unit may describe the ratio between the first relative efficiency and the second relative efficiency (conversion constant F(h)) by a polynomial with the arbitrary distance as a variable.

[0013] (8): A radioactivity measuring device (1) according to one aspect of the present invention includes a shield (9), a radiation detector (3), and a first relative efficiency (relative efficiency E h ) based on the second relative efficiency (relative efficiency E H ) and a processing unit (7) for acquiring the

[0014] (9): The radioactivity measuring device described in (8) above includes a radiation source installation jig (10, 20, 30, 40, 50) for positioning and fixing the radiation source, and the radiation detector is attached to the radiation source installation jig inside the shielding body.

[0015] (10): In the radioactivity measuring device described in (8) or (9) above, the processing unit describes the ratio between the first relative efficiency and the second relative efficiency (conversion constant F(h)) by a polynomial with the arbitrary distance as a variable. [Effects of the Invention]

[0016] According to the above (1), by providing the distance changing unit, the radiation source can be positioned and fixed at an arbitrary distance from a predetermined position. In the case of (2) above, even when the distance change unit changes the position of the radiation source relative to the predetermined position, it is possible to prevent the radiation source from being blocked from the predetermined position. In the case of (3) above, even if the distance from the predetermined position of the radiation source changes due to the movement of the moving part guided by the guide part, the display part can be used to set an arbitrary distance with high precision. In the case of (4) above, by selecting a distance changer supported by the support part from among a plurality of different distance changers, it is possible to position and fix the radiation source at an arbitrary distance from the predetermined position.

[0017] According to (5) above, by providing the distance changing unit, it is possible to position and fix the radiation source at an arbitrary distance from the radiation detector within various shielding bodies.

[0018] In the case of (6) above, even if the position of the radiation source with respect to the radiation detector is changed by the distance change unit, the relative efficiency (second relative efficiency) at a predetermined distance can be obtained. In the case of (7) above, the relative efficiency (second relative efficiency) at a predetermined distance can be easily obtained by a polynomial with an arbitrary distance as a variable.

[0019] According to (8) above, the relative efficiency (second relative efficiency) at a predetermined distance can be obtained based on the first relative efficiency at an arbitrary distance. In the case of (9) above, the radiation source can be positioned and fixed at an arbitrary distance from the radiation detector within various shielding bodies. In the case of (10) above, the relative efficiency (second relative efficiency) at a predetermined distance can be easily obtained by a polynomial with an arbitrary distance as a variable. [Brief explanation of the drawings]

[0020] [Figure 1] FIG. 1 is a block diagram showing the functional configuration of a radioactivity measuring device according to an embodiment of the present invention. [Figure 2] FIG. 1 is a cross-sectional view showing a configuration of a radiation source installation jig according to an embodiment of the present invention. [Figure 3] 10 is a graph showing an example of the correspondence relationship between the distance between the radiation source and the tip surface of the end cap housing of the radiation detector and the conversion constant in the radioactivity measurement device according to the embodiment of the present invention. FIG. [Figure 4] FIG. 4 is a cross-sectional view showing the configuration of a radiation source installation jig according to a first modified example of an embodiment of the present invention. [Figure 5] FIG. 10 is a cross-sectional view showing the configuration of a radiation source installation jig according to a second modified example of the embodiment of the present invention. [Figure 6] FIG. 10 is a cross-sectional view showing the configuration of a radiation source installation jig according to a second modified example of the embodiment of the present invention. [Figure 7] FIG. 10 is a cross-sectional view showing the configuration of a radiation source installation jig according to a third modified example of the embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0021] A radiation source installation jig and a radioactivity measurement device according to an embodiment of the present invention will be described below with reference to the accompanying drawings. The radioactivity measurement device according to the embodiment measures the radioactivity of a radiation source that emits radiation such as gamma rays, X-rays, beta rays, alpha rays, and neutron rays. Fig. 1 is a block diagram showing the functional configuration of a radioactivity measuring device 1 according to an embodiment. Fig. 2 is a cross-sectional view showing the configuration of a radiation source installation jig 10 according to an embodiment. As shown in FIG. 1, a radioactivity measuring device 1 of the embodiment includes, for example, a radiation detector 3, a multiple pulse-height analyzer 5, and a processing device .

[0022] The radiation detector 3 detects various types of radiation, such as gamma rays, X-rays, beta rays, and alpha rays. The radiation detector 3 may be, for example, a semiconductor detector using a semiconductor such as germanium, silicon, or a compound semiconductor (such as GaAs or CdTe), or a scintillation detector using various scintillators such as organic, inorganic, liquid, or gaseous. The radiation detector 3 of this embodiment is, for example, a germanium semiconductor detector equipped with a vertical cryostat. An end cap housing 3a having a radiation entrance window is provided at the tip of the cryostat. A germanium crystal sensitive to radiation is held in the vacuum region inside the end cap housing 3a.

[0023] The multi-pulse-height analyzer 5 is an MCA (Multi Channel Analyzer). The multi-pulse-height analyzer 5 calculates count values ​​for each of a plurality of channels associated with the pulse-height distribution of the output signal pulse (detection data) output from the radiation detector 3, that is, the pulse-height values. For example, when the radiation detector 3 outputs an output signal pulse having a pulse-height value corresponding to the energy of the radiation, the multi-pulse-height analyzer 5 creates an energy spectrum (spectral data) as the pulse-height distribution of the output signal pulse from the radiation detector 3.

[0024] The processing device 7 is an information processing device such as a personal computer, a smartphone, or a tablet terminal. A part of the processing device 7 includes a software function unit that functions when a processor such as a CPU (Central Processing Unit) executes a predetermined program. The software function unit is an ECU (Electronic Control Unit) that includes a processor such as a CPU, a ROM (Read Only Memory) that stores programs, a RAM (Random Access Memory) that temporarily stores data, and electronic circuits such as a timer. Note that a part of the processing device 7 may include an integrated circuit such as an LSI (Large Scale Integration).

[0025] The processing device 7 comprehensively controls the operations of, for example, the radiation detector 3, the multi-pulse-height analyzer 5, and auxiliary devices such as a sample changer. The processing device 7 performs processes such as calibration and inspection of the radiation detector 3 and the multi-pulse-height analyzer 5, spectral analysis, and nuclide analysis based on the energy spectrum of the radiation generated by the multi-pulse-height analyzer 5, for example. The processing device 7 includes an input unit such as a touch panel that outputs signals according to input operations by an operator, various switches, a keyboard, etc. The processing device 7 also includes an output unit such as a display device that displays various information and data, and a speaker that outputs various sounds, etc.

[0026] 2, the sensitive portion of the radiation detector 3 and the detection target such as the radiation source S are disposed inside a shielding body 9, for example. The shielding body 9 has an outer shape, for example, a box shape that surrounds the tip of the end cap housing 3a of the radiation detector 3 and the radiation source S. The radiation source S is positioned and fixed at a predetermined position, for example, away from the tip surface 3A of the end cap housing 3a of the radiation detector 3, by a radiation source installation jig 10. The shielding body 9 is formed of a radiation-shielding material such as lead or tungsten.

[0027] The radiation source installation jig 10 includes, for example, a support portion 11 and a plurality of different distance change portions 13. The outer shape of the support part 11 is, for example, cylindrical. The support part 11 has, for example, a first end part 11a and a second end part 11b at both ends in the axial direction along the central axis. The first end part 11a has, for example, an inner circumferential part that is expanded in diameter by one step, and is attached by fitting to the tip part of the end cap housing 3a of the radiation detector 3 along the axial direction. The second end part 11b has, for example, an inner circumferential part that is expanded in diameter by one step, and is attached by fitting to the distance change part 13 along the axial direction.

[0028] The plurality of different distance changers 13 include, for example, a first distance changer 13A(13) and a second distance changer 13B(13) having different axial lengths along the central axis. For example, the first distance changer 13A(13) is disposed inside the relatively large first shielding body 9A(9), and the second distance changer 13B(13) is disposed inside the relatively small second shielding body 9B(9). Each of the first distance changer 13A(13) and the second distance changer 13B(13) is selected, for example, so as to ensure a predetermined distance between the radiation source S and the top surface 9U of each of the shielding bodies 9A, 9B. The outer shape of each distance changer 13 is, for example, a cylindrical shape with one end (tip) in the axial direction covered. For example, the tip of each distance changer 13 forms a recess in which the radiation source S is placed and includes a radiation source holder 13a that holds the radiation source S. The radiation source holder 13a has, for example, a through-hole 13b formed therethrough in the axial direction. For example, the outer shape of each distance changer 13 has a shape and size that do not interfere with the through-hole 13b and the sensitive part of the radiation detector 3.

[0029] The processing device 7 calculates the relative efficiency E at a predetermined distance H between the radiation source S and the tip surface 3A of the radiation detector 3 in accordance with an appropriate distance changer 13 from among a plurality of distance changers 13 having different axial lengths selected according to, for example, the size of the shielding body 9. H The predetermined distance H is, for example, 250 mm. The processing device 7 calculates the relative efficiency E at a predetermined distance H as shown in the following formula (1), for example: H , the predetermined distance H related to the predetermined distance H e and a distance x related to an arbitrary distance x between the radiation source S and the tip surface 3A of the radiation detector 3. e and the relative efficiency E at distance x x The predetermined distance H e is, for example, the distance from the tip surface 3A of the end cap housing 3a of the radiation detector 3 to the radiation source S, the distance from the surface of a radiation-sensitive crystal arranged inside the end cap housing 3a to the radiation source S, or the distance from an arbitrary position in the radiation-sensitive crystal to the radiation source S. For example, when lithium or the like is deposited on the surface of a radiation-sensitive germanium crystal, the area where lithium is diffused near the surface of the germanium crystal becomes an insensitive layer, so by considering the distance from an arbitrary position in the crystal to the radiation source S, the relative efficiency E H The processing device 7 assumes that the inverse square law of distance can be applied to the relative efficiency, for example, based on the fact that the count rate of radiation obtained by the radiation detector 3 is inversely proportional to the square of the effective distance between the radiation source S and the radiation detector 3.

[0030]

number

[0031] As shown in the above formula (1) and the following formula (2), the processing device 7 calculates, for example, a relative efficiency E H and the relative efficiency E at any distance x x The conversion constant F(x), which is the ratio of x to x, is written as a polynomial of the distance x using appropriate constants a1, a2, and a3. Note that the polynomial of the distance x is not limited to a quadratic function as shown in the following formula (2), but may be an appropriate function of degree 3 or more.

[0032]

number

[0033] FIG. 3 is a graph showing an example of the correspondence relationship between the distance x between the radiation source S and the tip surface 3A of the end cap housing 3a of the radiation detector 3 and the conversion constant F(x) in the radioactivity measuring device 1 according to the embodiment. As shown in Figure 3, the relative efficiency E obtained at a given distance x is x The data of the conversion constant F(x) corresponding to is accurately approximated by the polynomial shown in the above equation (2). The processing device 7 calculates the relative efficiency E obtained at the distance h between the radiation source S and the tip surface 3A of the radiation detector 3, which is set by an appropriate distance change unit 13, as shown in the following formula (3), based on the above formula (2), for example: h and the conversion constant F(h) at distance h, the relative efficiency E at a given distance H is calculated as H Get.

[0034]

number

[0035] The processing device 7 sets, for example, the predetermined distance H and the constants a1, a2, and a3 in the above formula (3) as shown in the following formula (4).

[0036]

number

[0037] As described above, the radiation source installation jig 10 of the embodiment is provided with a plurality of different distance changers 13, thereby making it possible to position and fix the radiation source S at an arbitrary distance from the tip surface 3A of the radiation detector 3 within various shielding bodies 9. By selecting a distance changer 13 supported by the support part 11 from the plurality of different distance changers 13, the distance between the radiation source S and the tip surface 3A of the radiation detector 3 can be easily changed. The distance changer 13 does not interfere with the through-hole 13b of the radiation source holder 13a and the sensitive part of the radiation detector 3, so that the space between the radiation source S and the sensitive part of the radiation detector 3 can be prevented from being blocked.

[0038] Furthermore, according to the radioactivity measuring device 1 of the embodiment, even when the position of the radiation source S relative to the radiation detector 3 is changed by the distance change unit 13, the relative efficiency E H The relative efficiency E at any distance h h can be obtained based on the The conversion constant F(h) is written as a polynomial with the distance h as a variable, so the relative efficiency E at a given distance H is H can be easily obtained.

[0039] (Variation) Modifications of the embodiment will be described below. Note that the same parts as those in the above-described embodiment will be denoted by the same reference numerals, and descriptions thereof will be omitted or simplified. In the above-described embodiment, the distance between the radiation source S and the tip surface 3A of the radiation detector 3 is arbitrarily set by selecting one of a plurality of distance change units 13 having different axial lengths, but the present invention is not limited to this. FIG. 4 is a cross-sectional view showing the configuration of a radiation source installation jig 20 according to a first modified example of the embodiment. As shown in FIG. 4, a radiation source installation jig 20 according to the first modified example includes, for example, a support portion 11, a plurality of base-end distance change portions 21, a plurality of intermediate distance change portions 23, and a radiation source holding member 25. The outer shape of each of the base end distance changing unit 21 and the intermediate distance changing unit 23 is, for example, cylindrical. The outer shape of the radiation source holding member 25 is, for example, cylindrical with one end (tip) in the axial direction covered.

[0040] A first end 11a of the support part 11 is attached, for example, by fitting to the tip of the end cap housing 3a of the radiation detector 3. A base-end distance changer 21 is attached, for example, by fitting to a second end 11b of the support part 11. Each base-end distance changer 21 includes a tip portion 21a having an outer periphery that is reduced in diameter by one step at, for example, one end (tip) in the axial direction along the central axis. A first end portion 23a of the intermediate distance changer 23 is attached to the tip portion 21a by fitting along the axial direction, for example.

[0041] Each intermediate distance changer 23 has, for example, a first end 23a and a second end 23b at both ends in the axial direction along the central axis. The first end 23a has, for example, an inner circumferential portion that is expanded in diameter by one step, and is attached to the distal end 21a of the proximal distance changer 21 along the axial direction by fitting. The second end 23b has, for example, an outer circumferential portion that is reduced in diameter by one step, and is attached to the proximal end 25c of the radiation source holding member 25 along the axial direction by fitting.

[0042] The plurality of different base end distance changers 21 include, for example, a first base end distance changer 21A (21) and a second base end distance changer 21B (21) that have different axial lengths along the central axis. The plurality of different intermediate distance change portions 23 include, for example, a first intermediate distance change portion 23A (23) and a second intermediate distance change portion 23B (23) that have different axial lengths along the central axis. For example, the first base end side distance changer 21A (21) and the first intermediate distance changer 23A (23) are arranged inside a relatively large shielding body 9, and the second base end side distance changer 21B (21) and the second intermediate distance changer 23B (23) are arranged inside a relatively small shielding body 9. The base end side distance changer 21A, 21B and the intermediate distance changer 23A, 23B are selected, for example, so as to ensure a predetermined distance between the top surface 9U of each shielding body 9 and the radiation source S.

[0043] The radiation source holding member 25 has, for example, a recess in which the radiation source S is placed, and includes, at its axial tip, a radiation source holding part 25a that holds the radiation source S. The radiation source holding part 25a has, for example, a through-hole 25b that penetrates in the axial direction. For example, the radiation source holding member 25 and each distance changer 21, 23 have an outer shape and size that do not interfere with the through-hole 25b and the sensitive part of the radiation detector 3. The radiation source holding member 25 includes, for example, a base end portion 25c at one end (base end) in the axial direction along the central axis, which has an inner circumferential portion whose diameter is expanded by one step.

[0044] According to the first modified example, by replacing a plurality of different base end distance changing units 21 with a plurality of different intermediate distance changing units 23, the distance between the radiation source S and the distal end surface 3A of the radiation detector 3 can be easily changed.

[0045] FIG. 5 is a cross-sectional view showing the configuration of a radiation source installation jig 30 according to a second modified example of the embodiment. 5, the radiation source installation jig 30 according to the second modified example has, for example, a cylindrical outer shape. The radiation source installation jig 30 includes, for example, a support part 31, a plurality of base-side distance change parts 33, a plurality of intermediate distance change parts 35, and a radiation source holding member 37. The support portion 31 has, for example, a first end portion 31a and a second end portion 31b at both ends in the axial direction along the central axis. The first end portion 31a has, for example, an inner circumferential portion with a stepped diameter expansion, and is attached by fitting to the tip portion of the end cap housing 3a of the radiation detector 3 along the axial direction. The second end portion 31b has, for example, an inner circumferential portion with a stepped diameter expansion, and is attached by fitting to the first end portion 33a of the base-end distance changer 33 along the axial direction.

[0046] The multiple base-end distance changers 33, for example, have different axial lengths along the central axis. Each base-end distance changer 33, for example, has a first end 33a and a second end 33b at both ends in the axial direction. The first end 33a, for example, has an outer circumferential portion that is reduced in diameter by one step, and is attached to the second end 31b of the support portion 31 along the axial direction by fitting. The second end 33b, for example, has an inner circumferential portion that is expanded in diameter by one step, and is attached to the first end 35a of the intermediate distance changer 35 along the axial direction by fitting.

[0047] The intermediate distance changers 35 have, for example, different axial lengths along the central axis. Each intermediate distance changer 35 has, for example, a first end 35a and a second end 35b at both ends in the axial direction. The first end 35a has, for example, an outer circumferential portion that is reduced in diameter by one step, and is attached to the second end 33b of the base-end distance changer 33 along the axial direction by fitting. The second end 35b has, for example, an inner circumferential portion that is expanded in diameter by one step, and is attached to the base end 37c of the radiation source holding member 37 along the axial direction by fitting.

[0048] The radiation source holding member 37 has, for example, a recess in which the holder SH of the radiation source S is disposed and includes a holding portion 37a that holds the holder SH. The holding portion 37a has, for example, a through-hole 37b that penetrates in the axial direction. For example, the radiation source holding member 37 and the distance changers 33 and 35 have outer shapes and sizes that do not interfere with the through-hole 37b and the sensitive part of the radiation detector 3. The radiation source holding member 37 includes, for example, a base end portion 37c at one end (base end) in the axial direction along the central axis, the base end portion having an outer periphery whose diameter is reduced by one step.

[0049] FIG. 6 is a cross-sectional view showing the configuration of a radiation source installation jig 40 according to a second modified example of the embodiment. 6, the radiation source installation jig 40 according to the second modification has, for example, a cylindrical outer shape. The radiation source installation jig 40 includes, for example, a support part 41, a plurality of base-side distance change parts 43, a plurality of intermediate distance change parts 45, and a radiation source holding member 47. The support portion 41 has, for example, a first end portion 41a and a second end portion 41b at both ends in the axial direction along the central axis. The first end portion 41a has, for example, an inner circumferential portion that is expanded in diameter by one step, and is attached by fitting to the tip portion of the end cap housing 3a of the radiation detector 3 along the axial direction. The second end portion 41b has, for example, an outer circumferential portion that is reduced in diameter by one step, and is attached by fitting to the first end portion 43a of the base-end distance changer 43 along the axial direction.

[0050] The multiple base-end distance changers 43, for example, have different axial lengths along the central axis. Each base-end distance changer 43, for example, has a first end 43a and a second end 43b at both ends in the axial direction. The first end 43a, for example, has an inner circumferential portion that is expanded in diameter by one step, and is attached to the second end 41b of the support portion 41 along the axial direction by fitting. The second end 43b, for example, has an outer circumferential portion that is reduced in diameter by one step, and is attached to the first end 45a of the intermediate distance changer 45 along the axial direction by fitting.

[0051] The intermediate distance changers 45 have, for example, different axial lengths along the central axis. Each intermediate distance changer 45 has, for example, a first end 45a and a second end 45b at both ends in the axial direction. The first end 45a has, for example, an inner circumferential portion that is expanded in diameter by one step, and is attached to the second end 43b of the base-end distance changer 43 along the axial direction by fitting. The second end 45b has, for example, an outer circumferential portion that is reduced in diameter by one step, and is attached to the base end 47b of the radiation source holding member 47 along the axial direction by fitting.

[0052] The radiation source holding member 47 has, for example, a recess in which the holder SH of the radiation source S is placed and includes a holding portion 47a that holds the holder SH. The holding portion 47a has, for example, an inner circumferential portion that is expanded in diameter by one step, so that the holder SH is attached to the holding portion 47a. For example, the radiation source holding member 47 and the distance changers 43, 45 have outer shapes and sizes that do not interfere with the opening at the axial tip of the radiation source holding member 47 and the sensitive region of the radiation detector 3. The radiation source holding member 47 includes, for example, a base end portion 47b at one end (base end) in the axial direction along the central axis, which has an inner circumferential portion whose diameter is expanded by one step.

[0053] According to the second modified example, by replacing a plurality of different base end distance changing units 33, 43 with a plurality of different intermediate distance changing units 35, 45, the distance between the radiation source S and the distal end surface 3A of the radiation detector 3 can be easily changed.

[0054] FIG. 7 is a cross-sectional view showing the configuration of a radiation source installation jig 50 according to a third modified example of the embodiment. As shown in FIG. 7, a radiation source installation jig 50 according to the third modified example includes, for example, a support unit 51, a distance change unit 53, and a position display unit 55. The support portion 51 has, for example, a cylindrical outer shape. The distance change portion 53 has, for example, a cylindrical outer shape with one end (tip) in the axial direction covered.

[0055] The support part 51 has, for example, a base end part 51a having an inner circumferential part with a step-widened diameter at one end (tip) in the axial direction along the central axis. The base end part 51a is attached by fitting to the tip part of the end cap housing 3a of the radiation detector 3. The support part 51 has, for example, a female thread 51b on the inner circumferential part extending from the tip to the base end in the axial direction.

[0056] The distance changing unit 53 has, for example, a recess in which the radiation source S is placed and includes, at its axial tip, a radiation source holding unit 53a that holds the radiation source S. The radiation source holding unit 53a has, for example, a through-hole 53b that penetrates in the axial direction. For example, the outer shapes of the distance changing unit 53 and the support unit 51 are shaped and sized so as not to interfere with the through-hole 53b and the sensitive part of the radiation detector 3. The distance changer 53 has, for example, on its outer periphery extending from the base end to the tip in the axial direction, a male thread 53c that meshes with the female thread 51b of the supporter 51. The female thread 51b of the supporter 51 and the male thread 53c of the distance changer 53 move the distance changer 53 in the axial direction as the distance changer 53 rotates around the central axis, for example.

[0057] The position display unit 55 is provided, for example, on the inner periphery of the support unit 51. The position display unit 55 is, for example, a scale or the like that indicates the position of the base end of the distance change unit 53 in the axial direction. According to the third modification, the female thread 51b of the support part 51 and the male thread 53c of the distance change part 53 can move the distance change part 53 in the axial direction, thereby easily changing the distance between the radiation source S and the tip surface 3A of the radiation detector 3. The position display part 55 can be used to set any desired distance with high precision.

[0058] In the above-described embodiment, the processing device 7 calculates the relative efficiency E at a predetermined distance H when the position of the radiation source S is changed by the radiation source installation jig 10 having a plurality of different distance change units 13. H The relative efficiency E at any distance h hFor example, even in the case of a radiation source installation jig that does not include a plurality of different distance change units 13, that is, a case in which the position of the radiation source S with respect to the radiation detector 3 is fixed at a constant value (an arbitrary distance h), the processing device 7 can obtain the relative efficiency E at a predetermined distance H. H The relative efficiency E at any distance h h It may be obtained based on

[0059] The embodiments of the present invention are presented as examples and are not intended to limit the scope of the invention. These embodiments can be embodied in various other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their modifications are intended to be included within the scope and spirit of the invention, as well as within the scope of the invention and its equivalents as defined in the claims. [Explanation of symbols]

[0060] 1...radioactivity measuring device, 3...radiation detector, 5...multiple pulse height analyzer, 7...processing device, 9...shielding body, 10, 20, 30, 40, 50...radiation source installation jig, 11, 31, 41, 51...support part, 13, 53...distance changing part, 21, 33, 43...base end distance changing part, 23, 35, 45...intermediate distance changing part, 25, 37, 47...radiation source holding member, S...radiation source

Claims

1. A radiation source installation jig for positioning and fixing a radiation source, comprising: a distance changer for changing the distance between the radiation source and a predetermined position; Radiation source installation jig.

2. a radiation source holder that holds the radiation source and has a through hole that penetrates toward the predetermined position; The shape of the distance change portion is such that it does not interfere with the through hole and the predetermined position. The radiation source installation jig according to claim 1 .

3. a display unit that displays information about the distance between the radiation source and the predetermined position, The distance change unit a moving unit that moves between the predetermined position; a guide portion that guides the movement of the moving portion; Equipped with The radiation source installation jig according to claim 1 .

4. A support part is provided that supports the distance change part by fitting. The radiation source installation jig according to any one of claims 1 to 3.

5. The radiation source installation jig according to any one of claims 1 to 3; A shield; a radiation detector to which the radiation source installation jig is attached inside the shield; and Equipped with Radioactivity measuring device.

6. and a processing unit that acquires a second relative efficiency at a predetermined distance between the radiation source and the tip surface based on a first relative efficiency at an arbitrary distance between the radiation source and the tip surface of the end cap housing of the radiation detector. The radioactivity measuring device according to claim 5.

7. The processing unit The ratio between the first relative efficiency and the second relative efficiency is described by a polynomial with the arbitrary distance as a variable. The radioactivity measuring device according to claim 6.

8. A shield; a radiation detector; a processing unit that acquires a second relative efficiency at a predetermined distance between the radiation source and the tip surface based on a first relative efficiency at an arbitrary distance between the radiation source and the tip surface of the end cap housing of the radiation detector; Equipped with Radioactivity measuring device.

9. a radiation source installation jig for positioning and fixing the radiation source; The radiation detector has the radiation source installation jig attached inside the shielding body. The radioactivity measuring device according to claim 8.

10. The processing unit The ratio between the first relative efficiency and the second relative efficiency is described by a polynomial with the arbitrary distance as a variable. The radioactivity measuring device according to claim 8 or 9.

Images