Measurement device and measurement method

Abstract

To evaluate the contribution of high-energy neutrons and photons with which an object under measurement is irradiated.SOLUTION: A measurement device 10 includes a first measuring unit 12 located at a position where at least one of high-energy neutrons B1 and high-energy photons B2 emitted from a high-energy radiation source 96 is made incident, and a second measuring unit 14 located at a position farther away from the high-energy radiation source 96 than the first measuring unit 12 and not overlapping with the first measuring unit 12. The first measuring unit 12 includes a plurality of first converters each containing an element with a different atomic number, and the second measuring unit 14 includes a plurality of second converters each containing the same element as each of the plurality of first converters.SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] The present invention relates to a measuring apparatus and a measuring method using high-energy radiation.

Background Art

[0002] An inspection method for non-destructively penetrating inside a substance using neutrons is known, and is called neutron radiography testing (NRT) or neutron imaging. In neutron imaging, it is mainly used for the inspection of substances containing elements with a small atomic number that are considered difficult to inspect with X-rays. For example, it can be used for the inspection of water, oil or resin containing hydrogen (H), substances containing lithium (Li) or boron (B), etc. As a neutron source, for example, an accelerator neutron source that irradiates a target with high-energy particles such as protons or electrons accelerated using an accelerator to generate high-energy neutrons is utilized.

[0003] Since the mode of interaction between neutrons and substances changes depending on the energy of the neutrons, it is required to appropriately adjust and measure the energy (spectrum) of the neutrons used for the inspection. As a method for measuring the neutron spectrum, a method has been proposed in which a plurality of types of metal foil converters are irradiated with neutrons, and the intensity of the radiation emitted from each of the plurality of types of metal foil converters activated by the neutron irradiation is transferred to a transfer plate and measured (for example, Patent Document 1).

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] When irradiating a target with electrons to generate high-energy neutrons, high-energy photons (also called bremsstrahlung X-rays) are generated by the bremsstrahlung of the electrons, and radiation in which high-energy neutrons and photons are mixed is emitted. The high-energy photons interact with the object to be measured and activate the elements contained in the object to be measured. Depending on the type of element contained in the object to be measured, either the reaction with one of the neutrons or photons may be dominant, or the reaction with both neutrons and photons may be dominant. Also, depending on the type of element, the radioisotopes generated by the reaction with neutrons and the radioisotopes generated by the reaction with photons may be the same or different. Therefore, in analyzing the activated object to be measured, it is preferable to be able to grasp what kind of high-energy radiation the object to be measured was irradiated with.

[0006] One of the exemplary objects of an aspect of the present invention is to provide a technique for evaluating the contributions of high-energy neutrons and photons irradiated to an object to be measured.

Means for Solving the Problems

[0007] A measuring device according to an aspect of the present invention includes a first measuring unit disposed at a position where at least one of high-energy neutrons and high-energy photons emitted from a high-energy radiation source is incident, and a position that is farther from the high-energy radiation source than the first measuring unit and does not overlap with the first measuring unit, and a second measuring unit disposed at the position. The first measuring unit includes a plurality of first converters each containing an element with a different atomic number. The second measuring unit includes a plurality of second converters each containing the same element as each of the plurality of first converters.

[0008] Another aspect of the present invention is a measuring method. This method includes irradiating an object to be measured with high-energy photons, and measuring the radiation emitted from the object to be measured activated by the irradiation with high-energy photons.

[0009] Yet another aspect of the present invention is a measurement method. This method includes irradiating a first measurement unit with high-energy photons, irradiating a second measurement unit having a structure corresponding to the first measurement unit with high-energy neutrons, measuring radiation emitted from the first measurement unit activated by the irradiation of the high-energy photons to obtain a first measurement result, measuring radiation emitted from the second measurement unit activated by the irradiation of the high-energy neutrons to obtain a second measurement result, and comparing the first measurement result and the second measurement result.

[0010] In addition, any combination of the above components, or those obtained by mutually substituting the components and expressions of the present invention among methods, apparatuses, systems, etc., are also effective as aspects of the present invention.

Advantages of the Invention

[0011] According to an aspect of the present invention, the contributions of high-energy neutrons and photons irradiated to the object to be measured can be evaluated.

Brief Description of the Drawings

[0012]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

Embodiments for Carrying Out the Invention

[0013] Hereinafter, embodiments for carrying out the present invention will be described in detail. The configurations described below are examples and do not limit the scope of the present invention in any way. Also, in the description of the drawings, the same elements are denoted by the same reference numerals, and redundant descriptions are omitted as appropriate. Further, in the drawings referred to in the following description, the sizes and thicknesses of the respective constituent members are for convenience of explanation and do not necessarily indicate actual dimensions and ratios.

[0014] This embodiment relates to a technique for measuring a measurement object activated by irradiation with high-energy neutrons and photons emitted from a high-energy radiation source and evaluating the contributions of the neutrons and photons irradiated to the measurement object. "High energy" in this specification means that the energy of neutrons or photons is 1 MeV or more.

[0015] FIG. 1 is a diagram schematically showing an accelerator neutron source 90. The accelerator neutron source 90 includes an accelerator 92 and a target 94. The accelerator 92 is a device that accelerates the particle beam PB irradiated to the target 94, and is, for example, a linac or a cyclotron. The particle beam PB is an electron beam, a proton beam, an alpha beam, or the like. The accelerator 92 generates, for example, a particle beam PB accelerated to 10 MeV or more. The target 94 generates high-energy neutrons by a nuclear reaction due to irradiation with the particle beam PB. When the particle beam PB is an electron beam, the target 94 is a heavy metal such as tungsten (W) or lead (Pb). When the particle beam PB is a proton beam, the target 94 is a light metal such as beryllium (Be) or lithium (Li). The high-energy radiation source 96 is located inside the target 94 and is located at a location where the particle beam PB and the target 94 interact to generate neutrons.

[0016] FIG. 1 shows a case where the particle beam PB is an electron beam and the target 94 is a heavy metal such as tungsten (W). In this case, an electromagnetic cascade shower phenomenon occurs inside the target 94 irradiated with a high-energy electron beam, and high-energy neutrons B1 and high-energy photons B2 are emitted from the target 94. It is known that the first angular range θ1 in which the high-energy neutrons B1 are emitted is relatively large, and the second angular range θ2 in which the high-energy photons B2 are emitted is relatively small. Since the first angular range θ1 in which the high-energy neutrons B1 are emitted is large, the dose rapidly decreases as the distance from the high-energy radiation source 96 increases. On the other hand, since the second angular range θ2 in which the high-energy photons B2 are emitted is small, the dose decrease is small even when the distance from the high-energy radiation source 96 increases.

[0017] For example, at a position P0 that is close to the high-energy radiation source 96 and inside the second angular range θ2, the contributions of both the high-energy neutrons B1 and the high-energy photons B2 are large. On the other hand, at a position P1 that is close to the high-energy radiation source 96 and outside the second angular range θ2, the contribution of the high-energy neutrons B1 is large, but the contribution of the high-energy photons B2 is small. Also, at a position P1 that is far from the high-energy radiation source 96 and inside the second angular range θ2, the contribution of the high-energy neutrons B1 is small, but the contribution of the high-energy photons B2 is large. Therefore, when using the accelerator neutron source 90 as shown in FIG. 1, it is important to appropriately evaluate the respective contributions of the high-energy neutrons B1 and the high-energy photons B2.

[0018] Figs. 2(a) to (c) are diagrams showing an example of the object to be measured. Fig. 2(a) is an optical image of the object to be measured captured by a normal camera. The object to be measured is a semiconductor package mounted on a printed circuit board and is a memory board on which an SDRAM (Synchronous Dynamic Random Access Memory) is mounted. Fig. 2(b) is an image showing the two-dimensional intensity distribution of the radiation emitted from the activated object to be measured by irradiating the object to be measured in Fig. 2(a) with high-energy neutrons. Fig. 2(c) is an image showing the two-dimensional intensity distribution of the radiation emitted from the activated object to be measured by irradiating the object to be measured in Fig. 2(a) with high-energy photons. The two-dimensional intensity distribution of the radiation emitted from the object to be measured can be measured, for example, by transferring it to an imaging plate (IP) using a scintillating phosphor. As a method for measuring the two-dimensional intensity distribution of the radiation, for example, the content described in JP-A-2021-113758 can be used.

[0019] The images in Figs. 2(b) and (c) indicate that the darker (denser) the relative color, the higher the radiation intensity, and the lighter (thinner) the relative color, the lower the radiation intensity. As shown in Figs. 2(b) and (c), it can be seen that the locations that appear black due to activation differ depending on whether neutrons or photons are irradiated.

[0020] In Fig. 2(b), the semiconductor chip (or silicon die) located at the center of the semiconductor package and the printed circuit board around the semiconductor package are shown in black. In Fig. 2(b), it is presumed that copper (Cu) and gold (Au) used for the wiring of the semiconductor chip and the printed circuit board, and bromine (Br) resulting from hydrogen bromide (HBr) used for the etching of the semiconductor chip appear black due to activation.

[0021] In Fig. 2(c), the lead frame extending from the center to the outer periphery of the semiconductor package and the printed circuit board around the semiconductor package are shown in black. In Fig. 2(c), it is presumed that copper (Cu) used for the wiring of the printed circuit board and palladium (Pd) used for the lead frame appear black due to activation.

[0022] Thus, even for the same object to be measured, different images can be obtained in FIG. 2(b) using high-energy neutrons and FIG. 2(c) using high-energy photons. Further, by comparing FIG. 2(b) and FIG. 2(c), it is possible to identify the location where elements for which the reaction with high-energy neutrons is dominant are included and the location where elements for which the reaction with high-energy photons is dominant are included. As a result, it is possible to identify the locations where a plurality of types of elements existing inside the object to be measured are included. When used for such applications, it is important to appropriately evaluate the respective contributions of the high-energy neutron component and the high-energy photon component included in the high-energy radiation irradiated on the object to be measured.

[0023] (First Embodiment) FIG. 3 is a side view schematically showing the configuration of the measuring device 10 according to the first embodiment. The measuring device 10 includes a first measurement unit 12 and a second measurement unit 14.

[0024] The first measurement unit 12 is arranged at a position where at least one of the high-energy neutrons B1 and the high-energy photons B2 emitted from the high-energy radiation source 96 is incident. In the example of FIG. 3, the first measurement unit 12 is arranged in a first region where the high-energy neutrons B1 mainly enter and the high-energy photons B2 hardly enter. The first measurement unit 12 is arranged, for example, at a position that is at a first distance L1 from the high-energy radiation source 96.

[0025] The second measurement unit 14 is disposed at a position where at least one of the high-energy neutrons B1 and high-energy photons B2 emitted from the high-energy radiation source 96 is incident. In the example of FIG. 3, the second measurement unit 14 is disposed in a second region where the high-energy photons B2 mainly enter. The second measurement unit 14 is at a position different from that of the first measurement unit 12 as viewed from the high-energy radiation source 96 and is disposed at a position that does not overlap with the first measurement unit 12 as viewed from the high-energy radiation source 96. The second measurement unit 14 is disposed at a position farther from the high-energy radiation source 96 than the first measurement unit 12 as viewed from the high-energy radiation source 96, for example, at a position where the second distance L2 is formed from the high-energy radiation source 96. The second distance L2 is greater than the first distance L1.

[0026] The measuring device 10 can further include a fixing jig 20 for supporting the first measurement unit 12 and the second measurement unit 14. The fixing jig 20 can include a first support plate 22, a second support plate 24, a spacer 26, and a fastening member 28.

[0027] The first support plate 22 supports the first measurement unit 12. The first support plate 22 is disposed at a position of the first distance L1 from the high-energy radiation source 96. The first measurement unit 12 can be detachably attached to the surface of the first support plate 22. The first measurement unit 12 can be attached, for example, to the second surface 22b (or the back surface) opposite to the first surface 22a on which at least one of the high-energy neutrons B1 and high-energy photons B2 from the high-energy radiation source 96 is incident.

[0028] The second support plate 24 supports the second measurement unit 14. The second support plate 24 is disposed at a position of the second distance L2 from the high-energy radiation source 96. The second measurement unit 14 can be detachably attached to the surface of the second support plate 24. The second measurement unit 14 can be attached, for example, to the fourth surface 24b (or the back surface) opposite to the third surface 24a on which at least one of the high-energy neutrons B1 and high-energy photons B2 from the high-energy radiation source 96 is incident.

[0029] The first support plate 22 and the second support plate 24 are, for example, metal plates with a uniform thickness and flat. The first support plate 22 and the second support plate 24 are preferably made of a material that is difficult to shield the high-energy photon B2, and can be made of, for example, aluminum (Al). Aluminum (Al) is a material in which a photonuclear reaction that absorbs the high-energy photon B2 hardly occurs, so that the high-energy photon B2 can be transmitted without being shielded. The first support plate 22 and the second support plate 24 can be made of, for example, an Al plate containing 99% or more of Al, and have a thickness of about 0.1 mm to 5 mm. Since the reaction cross-section of the Al plate with the high-energy neutron B1 is small, even if the thicknesses of the first support plate 22 and the second support plate 24 are about several millimeters, the intensities of the high-energy neutrons B1 before and after passing through the first support plate 22 and the second support plate 24 hardly change.

[0030] The spacer 26 is disposed between the first support plate 22 and the second support plate 24 so as to fix the distance L from the first support plate 22 to the second support plate 24. The spacer 26, for example, makes the first support plate 22 and the second support plate 24 parallel to each other.

[0031] The fastening member 28 is a bolt, a screw, or the like, and fastens and fixes the first support plate 22 and the second support plate 24 to the spacer 26 to each other. The fixing jig 20 is configured such that the first support plate 22 and the second support plate 24 can be removed, for example, by removing the fastening member 28.

[0032] FIG. 4 is a diagram schematically showing a configuration example of the first measurement unit 12. The first measurement unit 12 includes a plurality of first converters 16a, 16b, 16c, 16d, 16e, 16f, 16g (collectively also referred to as the first converter 16). The plurality of first converters 16a to 16g are, for example, plate-like members having a uniform thickness of about 0.1 mm to 5 mm. The plurality of first converters 16a to 16g are attached to the surface of the first support plate 22 (for example, on the second surface or the back surface 22b). The plurality of first converters 16a to 16g can be detachably attached to the first support plate 22 using a resin adhesive or a double-sided tape. In the example of FIG. 4, seven first converters 16a to 16g are used, but the number of the plurality of first converters is not particularly limited and may be six or less or eight or more.

[0033] The first support plate 22 is provided with fixing holes 30 used for fixing by the fixing jig 20. The fixing holes 30 are through holes provided in the outer peripheral portion of the first support plate 22. In the example shown in FIG. 4, the outer shape of the first support plate 22 is square, and fixing holes 30 are provided at each of the four corners of the square. The outer shape of the first support plate 22 is not particularly limited, and the outer shape of the first support plate 22 may be circular or any polygon.

[0034] The plurality of first converters 16a to 16g are attached to the first region 32 of the first support plate 22. The first region 32 is a range in which high-energy neutrons B1 mainly enter and high-energy photons B2 substantially do not enter. The outer edge 32a of the first region 32 is a position corresponding to the first angular range θ1 in which high-energy neutrons B1 mainly enter. The inner edge 32b of the first region 32 is a position corresponding to the second region 34 (described later in FIG. 6) set on the second support plate 24. The inner edge 32b of the first region 32 may be a position corresponding to the second angular range θ2 in which high-energy photons B2 mainly enter. The first region 32 may include a first blank region 36 to which none of the plurality of first converters 16a to 16g are attached.

[0035] The plurality of first converters 16a to 16g can each be composed of a plate-like member containing an element with a different atomic number. As an element used for each of the plurality of first converters 16a to 16g, a metal element that is converted into another radioactive isotope that undergoes beta decay by a threshold reaction that absorbs high-energy neutrons can be used. As such a metal element, for example, aluminum (Al), zinc (Zn), molybdenum (Mo), gold (Au), copper (Cu), magnesium (Mg), or nickel (Ni) can be used. These metal elements are easy to measure the two-dimensional intensity distribution of radiation with high precision because the radioactive isotope generated by the reaction that absorbs neutrons or photons undergoes beta decay and emits beta rays. Also, these metal elements have high temporal convenience in measuring radiation because the half-life of the radioactive isotope is 0.1 hour or more and 200 hours or less.

[0036] FIG. 5 is a diagram showing the characteristics of the metal element used for the converter.

[0037] In the case of aluminum (Al), the isotope abundance ratio is 27 Al is 100%. 27 Al undergoes beta decay with a half-life of 9.458 minutes by the (n,p) reaction with a threshold energy of 1.896 MeV to - generate 27 Mg, and undergoes beta decay with a half-life of 14.959 hours by the (n,α) reaction with a threshold energy of 3.249 MeV to - generate 24 Na. 27 Al is an element in which photonuclear reactions are unlikely to occur, and the occurrence probability of (γ,n) reactions and (γ,p) reactions, which are photonuclear reactions, is extremely small compared to these threshold reactions that absorb neutrons. Therefore, 27 Al can be used as an element that reacts with high-energy neutrons but does not substantially react with high-energy photons.

[0038] In the case of zinc (Zn), various natural isotopes exist, and the isotope abundance ratio is 64 Zn is 48.63%, 66 Zn is 27.90%, 67Zn is 4.10%, 68 Zn is 18.75%, 70 Zn is 0.62%. Among these, 64 Zn undergoes β decay with a half-life of 12.7 hours through the (n,p) reaction with a threshold energy of 0.9 MeV - to decay 64 and produce Cu. 66 Zn undergoes β decay with a half-life of 5.12 minutes through the (n,p) reaction with a threshold energy of 1.887 MeV - to decay 66 and produce Cu. 64 Zn undergoes ε + β decay with a half-life of 9.186 hours through the (γ,2n) reaction which is a photonuclear reaction + to decay 62 and produce Zn. Also, 68 Zn undergoes β decay with a half-life of 61.83 h through the (γ,p) reaction which is a photonuclear reaction - to decay 67 and produce Cu. Therefore, Zn can be used as an element that reacts with both high-energy neutrons and high-energy photons. Since the isotopes produced are different in the reaction with high-energy neutrons and the reaction with high-energy photons, the isotopes produced can be identified by analyzing the γ-ray spectrum emitted from the isotopes produced, and the respective contributions of high-energy neutrons and high-energy photons can be analyzed.

[0039] In the case of molybdenum (Mo), the isotope abundance ratios are 92 Mo is 14.84%, 94 Mo is 9.25%, 95 Mo is 15.92%, 96 Mo is 16.68%, 97 Mo is 9.55%, 98 Mo is 24.13%, 100 Mo is 9.63%. Among these, 97 Mo undergoes β decay with a half-life of 23.25 hours through the (γ,p) reaction which is a photonuclear reaction - to decay 96 and produce Nb. 100 Mo undergoes β decay with a half-life of 65.94 hours through the (n,2n) reaction with a threshold energy of 8.373 MeV or the (γ,n) reaction which is a photonuclear reaction -Decay 99 Mo is produced. Therefore, Mo can be used as an element that reacts with both high-energy neutrons and high-energy photons. Since the same produced isotope can be generated by the reaction of high-energy neutrons and the reaction of high-energy photons, it is possible to analyze the combined contribution of high-energy neutrons and high-energy photons.

[0040] In the case of gold (Au), the isotope abundance is 197 Au is 100%. 197 Au undergoes β decay with a half-life of 6.183 days by the (n,2n) reaction or the (γ,n) reaction, which is a photonuclear reaction, with a threshold energy of 8.114 MeV. - Decay 196 Au is produced. Also, 197 Au mainly undergoes β decay with a half-life of 2.695 days by the (n,γ) reaction in the resonance region below 1 MeV. - Decay 198 Au is produced. Therefore, Au can be used as an element that reacts with both high-energy neutrons and high-energy photons. Since the same produced isotope can be generated by the reaction of high-energy neutrons and the reaction of high-energy photons, it is possible to analyze the combined contribution of high-energy neutrons and high-energy photons. Also, by measuring the energy of the γ-rays emitted from the produced isotope, 196 Au and 198 the production ratio of Au can be determined.

[0041] In the case of copper (Cu), the isotope abundance is 63 Cu is 69.17%, 65 Cu is 30.83%. Among these, 63 Cu undergoes β decay with a half-life of 12.7 hours by the (n,γ) reaction in the resonance region with an energy below 1 MeV and is converted to - Decay 64 Cu. Also, 65 Cu undergoes 65Ni is produced and undergoes β decay with a half-life of 12.7 hours through the (n,2n) reaction with a threshold energy of 10.06 MeV or the (γ,n) reaction which is a photonuclear reaction. - decays 64 to be converted to Cu. Therefore, Cu can be used as an element that reacts with both high-energy neutrons and high-energy photons. Since the same generated isotope can be produced in the reaction of high-energy neutrons and the reaction of high-energy photons, it is possible to analyze the combined contribution of high-energy neutrons and high-energy photons. However, it is also possible to distinguish the generated isotopes and determine the production ratio by measuring the energy of the γ-rays emitted from the generated isotopes.

[0042] In the case of magnesium (Mg), the isotope abundance is 24 Mg is 78.99%, 25 Mg is 10.00%, 26 Mg is 11.01%. Among these, 24 Mg undergoes β decay with a half-life of 14.96 hours through the (n,p) reaction with a threshold energy of 4.931 MeV or the (γ,p) reaction which is a photonuclear reaction. - decays 24 to produce Na. Therefore, Mg can be used as an element that reacts with both high-energy neutrons and high-energy photons. Since the same generated isotope can be produced in the reaction of high-energy neutrons and the reaction of high-energy photons, it is possible to analyze the combined contribution of high-energy neutrons and high-energy photons.

[0043] In the case of nickel (Ni), the isotope abundance is 0.93% 64 Ni mainly undergoes β decay with a half-life of 2.517 hours through the (n,γ) reaction in the resonance region where the energy is mainly less than 1 MeV. - decays 65 to be converted to Ni. Also, in the reaction of high-energy photons, 62 Ni with an isotope abundance of 3.63% is converted to 61 Co with a half-life of 1.65 hours through the (γ,p) reaction. By measuring the energy of the γ-rays emitted from the generated isotopes, 65 Ni and61 The production ratios can be determined by differentiating Co. Also, by utilizing the differences in the half-lives of the produced isotopes and varying the measurement timing or the transfer timing, it is possible to distinguish the produced isotopes.

[0044] As an element used for each of the plurality of first converters 16a to 16g, dysprosium (Dy) having a large reaction cross-section in the thermal neutron region may be further used. Dy can be used to measure neutrons in the thermal neutron region where the neutron energy is about 0.01 eV to 1 eV. Also, Au and Cu can also be used to measure neutrons in the epithermal neutron region or the resonance region where the neutron energy is about 1 eV to 0.1 MeV.

[0045] As an example of the element used for each of the plurality of first converters 16a to 16g, for example, Al, Zn, Mo, Au, Cu, Mg, and Dy can be used. For example, the plurality of first converters 16a to 16g can include an Al converter, a Zn converter, a Mo converter, an Au converter, a Cu converter, a Mg converter, and a Dy converter.

[0046] FIG. 6 is a diagram schematically showing a configuration example of the second measurement unit 14. The second measurement unit 14 includes a plurality of second converters 18a, 18b, 18c, 18d, 18e, 18f, 18g (collectively also referred to as the second converter 18). The plurality of second converters 18a to 18g are, for example, plate-like members having a uniform thickness of about 0.1 mm to 5 mm. The plurality of second converters 18a to 18g are attached to the surface of the second support plate 24 (for example, on the fourth surface or the back surface 24b). The plurality of second converters 18a to 18g can be detachably attached to the second support plate 24 using a resin adhesive or double-sided tape. In the example of FIG. 4, seven second converters 18a to 18g are used, but the number of the plurality of second converters is not particularly limited and may be 6 or less, or 8 or more.

[0047] The second support plate 24 is provided with fixing holes 30 used for fixing by the fixing jig 20. The fixing holes 30 are through holes provided in the outer peripheral portion of the second support plate 24. In the example shown in FIG. 6, the outer shape of the second support plate 24 is square, and fixing holes 30 are provided at each of the four corners of the square. The outer shape of the second support plate 24 is not particularly limited, and the outer shape of the second support plate 24 may be circular or any polygon.

[0048] The plurality of second converters 18a to 18g are attached to the second region 34 of the second support plate 24. The second region 34 is a range where the high-energy photons B2 mainly enter. The outer edge 34a of the second region 34 is a position corresponding to the second angle θ2 at which the high-energy photons B2 mainly enter. The second region 34 may include a second blank region 38 to which none of the plurality of second converters 18a to 18g are attached.

[0049] The plurality of second converters 18a to 18g can be constituted by plate-like members containing the same elements as those of the plurality of first converters 16a to 16g respectively. The plurality of second converters 18a to 18g may be configured to have the same thickness and size as those of the plurality of first converters 16a to 16g respectively. That is, the set of the plurality of second converters 18a to 18g may be the same as the set of the plurality of first converters 16a to 16g. For example, the plurality of second converters 18a to 18g can include an Al converter, a Zn converter, a Mo converter, an Au converter, a Cu converter, a Mg converter, and a Dy converter.

[0050] FIG. 7 is a flowchart showing the flow of the measurement method according to the first embodiment. First, the measuring device 10 is positioned based on the position of the high-energy radiation source 96 (S10). For example, based on the position of the target 94 of the accelerator neutron source 90, the measuring device 10 can be positioned using a surveying instrument such as a laser alignment device (laser theodolite).

[0051] Next, at least one of the high-energy neutrons B1 and the high-energy photons B2 to be measured is irradiated onto the installed measuring device 10 (S12). In the case of the accelerator neutron source 90 shown in FIG. 1, both the high-energy neutrons B1 and the high-energy photons B2 are irradiated onto the measuring device 10. Depending on the type of high-energy radiation source, only the high-energy neutrons B1 may be irradiated onto the measuring device 10, or only the high-energy photons B2 may be irradiated onto the measuring device 10. When at least one of the high-energy neutrons B1 and the high-energy photons B2 is irradiated, a plurality of first converters 16a to 16g included in the first measurement unit 12 and a plurality of second converters 18a to 18g included in the second measurement unit 14 become radioactive.

[0052] Next, the first measurement unit 12 is removed from the measuring device 10, and the radiation emitted from the first measurement unit 12 is measured to obtain a first measurement result (S14). For example, by using an imaging plate, the beta rays emitted from the first measurement unit 12 can be measured. Also, by using a germanium (Ge) semiconductor detector, the spectrum of the gamma rays emitted from the first measurement unit 12 can be measured. Further, by analyzing the spectrum of the gamma rays, the nuclide and the production amount of the radioisotope generated in each of the plurality of first converters 16a to 16g can be specified.

[0053] Also, the second measurement unit 14 is removed from the measuring device 10, and the radiation emitted from the second measurement unit 14 is measured to obtain a second measurement result (S16). For example, by using an imaging plate, the beta rays emitted from the second measurement unit 14 can be measured. Also, by using a germanium (Ge) semiconductor detector, the spectrum of the gamma rays emitted from the second measurement unit 14 can be measured. Further, by analyzing the spectrum of the gamma rays, the nuclide and the production amount of the radioisotope generated in each of the plurality of second converters 18a to 18g can be specified. Note that the order of the measurement in S14 and the measurement in S16 is not limited, and the measurements in S14 and S16 may be performed simultaneously.

[0054] Next, the first measurement result and the second measurement result are compared (S18). By comparing the first measurement result and the second measurement result, it is possible to compare the contributions of the neutron component and the photon component in the first region 32 where the first measurement unit 12 is provided with the contributions of the neutron component and the photon component in the second region 34 where the second measurement unit 14 is provided. For example, by comparing the measurement results of the first converter 16 and the second converter 18 containing the same element, it is possible to compare the contributions of the neutron component and the photon component irradiated to each of the first converter 16 and the second converter 18. For example, by comparing the measurement results of the first converter 16 and the second converter 18 containing Al, the difference in the contribution of the neutron component in each of the first region 32 and the second region 34 can be evaluated. Also, by comparing the measurement results of the first converter 16 and the second converter 18 containing Zn, the difference in the contributions of the neutron component and the photon component in each of the first region 32 and the second region 34 can be evaluated. Also, by comparing the measurement results of the first converter 16 and the second converter 18 containing Mo, the difference in the total contribution of the neutron component and the photon component in each of the first region 32 and the second region 34 can be evaluated. Furthermore, by comparing the measurement result of the Al converter with the measurement result of a converter other than Al (for example, a Zn converter or a Mo converter, etc.), the respective contributions of the neutron component and the photon component in each of the first region 32 and the second region 34 can be evaluated.

[0055] Note that not only the first measurement unit 12 and the second measurement unit 14 are measured, but also the radiation emitted from each of the first support plate 22 and the second support plate 24 to which the first measurement unit 12 and the second measurement unit 14 are respectively attached may be further measured.

[0056] The first support plate 22 is activated by secondary neutrons because it is irradiated with secondary neutrons emitted from the first measurement unit due to a nuclear reaction occurring in the first measurement unit 12. Specifically, activation by secondary neutrons occurs at locations on the first support plate 22 where each of the plurality of converters 16a to 16g is attached. For example, by comparing the measurement results at locations on the first support plate 22 where each of the plurality of first converters 16a to 16g is attached with the measurement results of the first blank region 36 where no first converter is attached, the contribution of secondary neutrons can be evaluated. Also, by comparing the measurement results at a plurality of locations on the first support plate 22 where the plurality of first converters 16a to 16g are attached, the contributions of high-energy neutrons and high-energy photons that cause the nuclear reactions in which secondary neutrons are generated at each of the plurality of first converters 16a to 16g can be evaluated.

[0057] Similarly, by comparing the measurement results at locations on the second support plate 24 where each of the plurality of second converters 18a to 18g is attached with the measurement results of the second blank region 38 where no second converter is attached, the contribution of secondary neutrons can be evaluated. Also, by comparing the measurement results at a plurality of locations on the second support plate 24 where the plurality of second converters 18a to 18g are attached, the contributions of high-energy neutrons and high-energy photons that cause the nuclear reactions in which secondary neutrons are generated at each of the plurality of second converters 18a to 18g can be evaluated. Furthermore, by comparing the measurement results at a plurality of locations on the first support plate 22 where the plurality of first converters 16a to 16g are attached with the measurement results at a plurality of locations on the second support plate 24 where the plurality of second converters 18a to 18g are attached, the contributions of the high-energy neutron component or the high-energy photon component irradiated to each of the first region 32 and the second region 34 can be evaluated.

[0058] By measuring the contribution of secondary neutrons using the first support plate 22 or the second support plate 24, it is possible to evaluate a nuclear reaction in which an isotope with a very short half-life generated by the first converter or the second converter is generated. For example, when the half-life of the generated isotope is a very short time such as less than 0.1 hour or less than 1 minute, most of the generated isotope will be lost due to the elapsed time until the first converter or the second converter is taken out and measured after irradiation with high-energy radiation, making the measurement very difficult. On the other hand, when the first support plate 22 or the second support plate 24 is an Al plate, an isotope with a relatively long half-life (for example 24 Na) is generated by the nuclear reaction of secondary neutrons, so even if it takes time to take out the first support plate 22 or the second support plate 24 and measure it after irradiation with high-energy radiation, the measurement is still possible sufficiently.

[0059] According to the present embodiment, using the measuring device 10, it is possible to evaluate the contributions of the high-energy neutrons B1 and high-energy photons B2 irradiated from the high-energy radiation source 96. For example, when measuring an object to be measured using at least one of the high-energy neutrons B1 and high-energy photons B2 irradiated from the high-energy radiation source 96 and acquiring an image as shown in FIGS. 2(b) and (c), the measured image can be appropriately analyzed. In particular, it is possible to appropriately evaluate which contribution of the neutron component and the photon component is large in the measured image.

[0060] (Second Embodiment) FIGS. 8 and 9 are plan views schematically showing the configuration of the measuring device 10A according to the second embodiment. The measuring device 10A according to the second embodiment has the same configuration as the measuring device 10 according to the first embodiment shown in FIG. 3, but the configurations of the first measuring unit 12A shown in FIG. 8 and the second measuring unit 14A shown in FIG. 9 are different from those of the first embodiment. Hereinafter, the second embodiment will be described centering on the differences from the first embodiment, and the common points will be omitted as appropriate.

[0061] The measuring device 10A includes a first measuring unit 12A and a second measuring unit 14A. The measuring device 10A can further include a fixing jig 20. The fixing jig 20 can be configured in the same manner as in the first embodiment.

[0062] FIG. 8 shows the configuration of the first measuring unit 12A according to the second embodiment, corresponding to FIG. 4 described above. The first measuring unit 12A includes a first object to be measured 42 and a plurality of first converters 46a, 46b, 46c, 46d, 46e, 46f (collectively also referred to as the first converter 46). The first object to be measured 42 and the plurality of first converters 46a to 46f are arranged in the first region 32 of the first support plate 22.

[0063] The first object to be measured 42 is an object to be measured using at least one of high-energy neutrons B1 and high-energy photons B2 emitted from the high-energy radiation source 96. The first object to be measured 42 is not particularly limited, but is, for example, a semiconductor device such as a semiconductor package, and is a CPU (Central Processing Unit), GPU (Graphics Processing Unit), NPU (Neural Processing Unit), memory, power semiconductor element, semiconductor imaging element, transistor, thyristor, LED, diode, or solar cell element, etc. The first object to be measured 42 can be detachably attached to the first support plate 22 using a resin adhesive or a double-sided tape, etc.

[0064] The plurality of first converters 46a to 46f are plate-like members having a uniform thickness of about 0.1 mm to 5 mm, for example. The plurality of first converters 46a to 46f can be detachably attached to the first support plate 22 using a resin adhesive, double-sided tape, or the like. Each of the plurality of first converters 46a to 46f contains, for example, an element assumed to be contained in the first object to be measured 42. Each of the plurality of first converters 46a to 46f may contain, for example, a metal element or a semiconductor element. At least one of the plurality of first converters 46a to 46f may contain the same metal element as the first converter according to the above-described first embodiment. At least one of the plurality of first converters 46a to 46f may contain a semiconductor element such as silicon (Si) or germanium (Ge), or may contain a compound semiconductor such as a III-V group semiconductor, a II-VI group semiconductor, or a IV-IV group semiconductor. As elements used for the compound semiconductor, for example, indium (In), gallium (Ga), arsenic (As), antimony (Sb), phosphorus (P), or the like can be used.

[0065] FIG. 9 shows the configuration of the second measurement unit 14A according to the second embodiment, corresponding to FIG. 6 described above. The second measurement unit 14A includes a second object to be measured 44 and a plurality of second converters 48a, 48b, 48c, 48d, 48e, 48f (also collectively referred to as the second converter 48). The second object to be measured 44 and the plurality of second converters 48a to 48f are arranged in the second region 34 of the second support plate 24.

[0066] The second object to be measured 44 is an object to be measured using at least one of high-energy neutrons B1 and high-energy photons B2 emitted from the high-energy radiation source 96, and has the same structure as the first object to be measured 42. The first object to be measured 42 and the second object to be measured 44 are, for example, the same product produced in the same lot. The second object to be measured 44 can be detachably attached to the second support plate 24 using a resin adhesive, double-sided tape, or the like.

[0067] The plurality of second converters 48a to 48f can be composed of plate-like members containing the same elements as those of the plurality of first converters 46a to 46f respectively. The plurality of second converters 48a to 48f may be configured to have the same thickness and size as those of the plurality of first converters 46a to 46f respectively.

[0068] Also in the present embodiment, the same method as that in the first embodiment shown in FIG. 7 described above can be used. In the second embodiment, the measurement result of the radiation emitted from the first object to be measured 42, the measurement result of the radiation emitted from the second object to be measured 44, the measurement result of the radiation emitted from each of the plurality of first converters 46a to 46f, and the measurement result of the radiation emitted from each of the plurality of second converters 48a to 48f can be used. Also in the second embodiment, the measurement result of the radiation emitted from the first support plate 22 that supports the first measurement unit 12A and the measurement result of the radiation emitted from the second support plate 24 that supports the second measurement unit 14A may be further used. For the measurement of the radiation, an imaging plate may be used, or a Ge semiconductor detector may be used.

[0069] According to the second embodiment, images of the first object to be measured 42 and the second object to be measured 44 activated by at least one of the high-energy neutrons B1 and the high-energy photons B2 can be obtained. For example, images as shown in FIGS. 2(b) and (c) can be obtained. According to the second embodiment, by using the measurement results of the first converter and the second converter containing the elements included in the first object to be measured 42 and the second object to be measured 44 as references, the elements included in the first object to be measured 42 and the second object to be measured 44 can be quantitatively analyzed. By using the measurement results of the first support plate 22 and the second support plate 24, the contribution of the isotopes with very short half-lives generated in the first object to be measured 42 and the second object to be measured 44 can also be evaluated.

[0070] (Third Embodiment) FIG. 10 is a side view schematically showing the configuration of a measuring device 10B according to a third embodiment. The measuring device 10B according to the third embodiment has the same configuration as the measuring device 10 according to the first embodiment shown in FIG. 3, but is different from the first embodiment in that a shielding body for shielding high-energy photons is provided between the first measuring unit 12 and the second measuring unit 14. Hereinafter, the third embodiment will be described centering on the differences from the first embodiment, and the common points will be omitted as appropriate.

[0071] The high-energy radiation B3 incident on the measuring device 10B is, for example, cosmic rays from the sun, and is incident on the measuring device 10B with a uniform intensity distribution. In this case, the high-energy radiation source is the sun. The high-energy radiation B3 may include at least one of a high-energy neutron component and a high-energy photon component, but the ratio of these contributions is unknown.

[0072] The measuring device 10B includes a first measuring unit 12, a second measuring unit 14, and a shielding body 50. The first measuring unit 12 and the second measuring unit 14 can be configured in the same manner as in the first embodiment. The first measuring unit 12 and the second measuring unit 14 may be configured in the same manner as in the second embodiment.

[0073] The measuring device 10B can further include a fixing jig 20B. The fixing jig 20B includes a first support plate 22, a second support plate 24, a spacer 26, a fastening member 28, and an intermediate support plate 56. The intermediate support plate 56 is disposed between the first support plate 22 and the second support plate 24 and supports the shielding body 50. In the example shown in FIG. 10, three intermediate support plates 56 are arranged, and the first shielding body 52 and the second shielding body 54 are attached to two of the intermediate support plates 56. The spacer 26 is disposed between the first support plate 22, the second support plate 24, and the intermediate support plate 56 to make them parallel to each other. The fastening member 28 fastens and fixes the first support plate 22, the second support plate 24, the intermediate support plate 56, and the spacer 26 to each other.

[0074] The shielding body 50 is configured to shield the high-energy photon component among the high-energy radiation B3 directed toward the second measurement unit 14. The shielding body 50 is disposed at a position overlapping the second measurement unit 14 when viewed in the incident direction of the high-energy radiation B3.

[0075] The shielding body 50 can include a first shielding body 52 and a second shielding body 54. When viewed in the incident direction of the high-energy radiation B3, the first shielding body 52 is disposed on the upstream side, and the second shielding body 54 is disposed on the downstream side. That is, the second shielding body 54 is disposed between the first shielding body 52 and the second measurement unit 14.

[0076] The first shielding body 52 can be formed of, for example, a block of iron (Fe). The thickness of the first shielding body 52 is, for example, 50 mm or more and 100 mm or less. The second shielding body 54 can be formed of a block containing an element having an atomic number larger than that of the first shielding body 52, and can be formed of, for example, a block of lead (Pb), tungsten (W), or molybdenum (Mo). The thickness of the second shielding body 54 is, for example, 50 mm or more and 100 mm or less. The thickness of the second shielding body 54 may be smaller than the thickness of the first shielding body 52. Since the proportion of neutrons due to the (γ,n) reaction, which is a photonuclear reaction, is smaller in Fe used for the first shielding body 52 than in Pb, W, or Mo used for the second shielding body 54, the generation amount of secondary neutrons accompanying the photonuclear reaction can be suppressed. After shielding a certain amount of photons with the first shielding body 52, by shielding the photons with the second shielding body 54 formed of Pb, W, or Mo, the generation amount of secondary neutrons accompanying the photonuclear reaction in the second shielding body 54 can be suppressed.

[0077] According to the third embodiment, high-energy radiation B3 can be measured using the first measurement unit 12. Further, among the high-energy radiation B3 heading toward the second measurement unit 14, the photon component is shielded by the shielding body 50, so that the neutron component of the high-energy radiation B3 can be measured by the second measurement unit 14. Therefore, by comparing the first measurement result using the first measurement unit 12 and the second measurement result using the second measurement unit 14, the respective contributions of the neutron component and the photon component in the high-energy radiation B3 can be measured. Thereby, the neutron component and the photon component included in the unknown high-energy radiation B3 such as cosmic rays can be evaluated.

[0078] In the present embodiment, each of the first measurement unit 12 and the second measurement unit 14 may include an object to be measured such as a semiconductor device, similarly to the second embodiment. In this case, the influence of the high-energy radiation irradiated on the semiconductor device can be evaluated. For example, semiconductor devices used in a space environment such as artificial satellites and space probes are irradiated with high-energy radiation, and it is known that the irradiation with high-energy radiation may lead to abnormal operations and failures. According to the present embodiment, for example, the respective influences of the high-energy neutron component and the high-energy photon component irradiated on the semiconductor device can be distinguished and evaluated.

[0079] As described above, the present invention has been described based on the embodiments. It is understood by those skilled in the art that the present invention is not limited to the above embodiments, various design changes are possible, various modifications are possible, and such modifications are also within the scope of the present invention.

[0080] In the above-described embodiment, the case where a stimulable phosphor is used as the imaging plate has been shown, but other types of phosphors may be used, or a combination of a lead foil intensifying screen and a photosensitive film may be used.

Explanation of Reference Numerals

[0081] 10, 10A, 10B... measuring devices, 12, 12A... first measurement units, 14, 14A... second measurement units, 16, 46... first converters, 18, 48... second converters, 22... first support plates, 24... second support plates, 42... first objects to be measured, 44... second objects to be measured, 96... high-energy radiation sources, B1... high-energy neutrons, B2... high-energy photons, B3... high-energy radiation.

Claims

1. A first measurement unit disposed at a position where at least one of high-energy neutrons and high-energy photons emitted from a high-energy radiation source is incident; A second measurement unit disposed at a position farther from the high-energy radiation source than the first measurement unit and not overlapping with the first measurement unit; and the measurement apparatus comprising: The first measurement unit includes a plurality of first converters each containing an element having a different atomic number; The second measurement unit includes a plurality of second converters each containing the same element as each of the plurality of first converters.

2. The first measurement unit further includes a first object to be measured; The second measurement unit further includes a second object to be measured having the same structure as the first object to be measured. The measurement apparatus according to claim 1.

3. At least one of the plurality of first converters contains an element included in the first object to be measured; At least one of the plurality of second converters contains an element included in the second object to be measured. The measurement apparatus according to claim 2.

4. The first object to be measured and the second object to be measured are semiconductor devices. The measurement apparatus according to claim 2.

5. At least one of the plurality of first converters and at least one of the plurality of second converters contain aluminum (Al), zinc (Zn), molybdenum (Mo), gold (Au), copper (Cu), magnesium (Mg), nickel (Ni), or dysprosium (Dy). The measurement apparatus according to any one of claims 1 to 4.

6. At least one first converter among the plurality of first converters and at least one second converter among the plurality of second converters contain a semiconductor element or a compound semiconductor, and the measuring device according to any one of claims 1 to 4.

7. The plurality of first converters are arranged side by side on a first support plate, The plurality of second converters are arranged side by side on a second support plate, and the measuring device according to any one of claims 1 to 4.

8. A shielding body is provided between the high-energy radiation source and the second measuring unit to shield high-energy photons, and the measuring device according to any one of claims 1 to 4.

9. Irradiating the first measuring unit with high-energy neutrons, Irradiating the second measuring unit having a structure corresponding to the first measuring unit with high-energy photons, Measuring the radiation emitted from the first measuring unit activated by the irradiation of the high-energy neutrons to obtain a first measurement result, Measuring the radiation emitted from the second measuring unit activated by the irradiation of the high-energy photons to obtain a second measurement result, And comparing the first measurement result and the second measurement result, and a measuring method comprising the steps of.

10. Irradiating the object to be measured with high-energy photons, And measuring the radiation emitted from the object to be measured activated by the irradiation of the high-energy photons, and a measuring method comprising the steps of.

11. The object to be measured is irradiated with the high-energy photons while being located on a support plate, and the support plate is activated by secondary neutrons emitted from the object to be measured by a photonuclear reaction due to the irradiation of the high-energy photons, The measuring method according to claim 10, further comprising measuring the radiation emitted from the support plate activated by the secondary neutrons.

Images