Radiation monitor and method for detecting radiation

Abstract

To provide a radiation monitor capable of flattening the energy properties of sensitivity emitting photons to an incident radiation by a small and single radiation detection part.SOLUTION: A radiation monitor includes a radiation detection part 2 including a phosphor emitting photons to an incident radiation and a photon transmission part 7 for transmitting the photons emitted from the phosphor of the radiation detection part. The phosphor includes first and second phosphors 4 and 5, adjacent to each other and arranged in parallel and a photon reflection layer 6 between the first and second phosphors; and the first phosphor, the photon reflection layer, and the second phosphor contact the photon transmission part.SELECTED DRAWING: Figure 1A

Description

Technical Field

[0001] The present invention relates to a radiation monitor and a method for detecting radiation.

Background Art

[0002] Conventionally, as a radiation monitor for measuring the radiation dose rate, an ionization chamber, a GM counter tube (Geiger-Muller counter), a scintillation detector, and a semiconductor detector have been used. In particular, a semiconductor detector is applied to a radiation monitor capable of measuring in a low dose rate environment. A radiation monitor using a semiconductor detector is used, for example, in a nuclear power plant, a nuclear fuel reprocessing facility, a medical facility using radioactive isotopes, an industrial facility, a research accelerator facility, a general environmental monitoring device, and the like.

[0003] A radiation monitor using a semiconductor detector utilizes electron-hole pairs generated by radiation incidence, and derives the dose rate from the counting rate of electrical pulses generated by the voltage applied to the semiconductor. On the other hand, since a high voltage is applied to the semiconductor detector, there is a risk of explosion when the hydrogen concentration in the air is high. In addition, since an electrical pulse signal generated from the semiconductor is used, there is a possibility of transmitting and receiving electrical noise to other measuring devices.

[0004] Also, as a detector capable of explosion protection and suppression of electrical noise, there is an optical fiber type radiation detector. The optical fiber type radiation detector transmits a plurality of photons generated with respect to incident radiation through an optical fiber, and measures the dose rate from the single photon counting rate. Therefore, power supply to the radiation detection unit is unnecessary, and transmission and reception of electrical noise can be suppressed. As a technology in this field, for example, there is Patent Document 1.

[0005] In the [Summary] of Patent Document 1, it is described that "[Problem] To provide a radiation monitor that suppresses the risk of explosion or the like and can simply and accurately measure the radiation dose rate. [Solution] The radiation monitor 100 of the present invention includes a radiation emitting element 10 having a light emitting unit 11 that emits light with an intensity corresponding to the dose rate of the incident radiation, an optical fiber 20 connected to the radiation emitting element 10 that transmits the light emitted from the light emitting unit 11, an electrical pulse converter 30 connected to the optical fiber 20 that emits one electrical pulse for each photon of the transmitted light, an electrical pulse detector 40 connected to the electrical pulse converter 30 that counts the electrical pulses emitted from the electrical pulse converter 30, and an analyzer 50 connected to the electrical pulse detector 40 that converts the counting rate of the electrical pulses counted by the electrical pulse detector 40 into the radiation dose rate." The technology of the radiation monitor is disclosed. Further, in Patent Document 1, as a light emitting unit that emits light with an intensity corresponding to the dose rate of the incident radiation, for example, a technology is shown in which it is formed by a light transmissive material of transparent yttrium aluminum garnet as a base material and rare earth elements such as ytterbium, neodymium, cerium, and praseodymium contained in this light transmissive material.

[0006] In addition, the measurement of the dose rate of the radiation monitor is used in an environment where radiation of various energies and irradiation directions is mixed, and an improvement in the measurement accuracy of the dose rate is desired. The reason is that the radiation detection unit has different measurement sensitivities depending on the energy of the incident radiation. Generally, it is considered useful to flatten the energy characteristics by using a metal shielding body capable of attenuating the radiation intensity or by installing correction detection units in parallel.

Prior Art Documents

Patent Documents

[0007]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0008] However, in order to flatten the energy characteristics, there are problems with the handleability due to the increase in size and weight of the radiation detection unit, and the complication of the system and the increase in cost due to parallelization. Alternatively, flattening the energy characteristics with a small and single radiation detection unit becomes a problem.

[0009] An object of the present invention is to provide a radiation monitor that can flatten the energy characteristics of sensitivity to emit photons with respect to incident radiation with a small and single radiation detection unit.

Means for Solving the Problems

[0010] In order to solve the above problems, the present invention is configured as follows. That is, the radiation monitor of the present invention includes a radiation detection unit having a phosphor that emits photons with respect to incident radiation, and a photon transmission unit that transmits photons emitted from the phosphor of the radiation detection unit. The phosphor has a first phosphor and a second phosphor. The first phosphor and the second phosphor are adjacent to each other and arranged in parallel, and there is a photon reflection layer between the first phosphor and the second phosphor. The first phosphor, the photon reflection layer, and the second phosphor are in contact with the photon transmission unit. Moreover, the radiation detection unit is configured with a structure in which radiation is incident in the order of the first phosphor, the photon reflection layer, and the second phosphor, and the contact area between the second phosphor and the photon transmission unit is larger than the contact area between the first phosphor and the photon transmission unit. It is characterized by this.

[0011] Other means will be described in the mode for carrying out the invention.

Effects of the Invention

[0012] According to the present invention, it is possible to provide a radiation monitor that can flatten the energy characteristics of sensitivity to emit photons with respect to incident radiation with a small and single radiation detection unit.

Brief Description of the Drawings

[0013]

Figure 1A

Figure 1B

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9A

Figure 9B

Figure 10

Figure 11

Figure 12

Figure 13

Figure 14

Embodiments for Carrying Out the Invention

[0014] Hereinafter, embodiments for carrying out the present invention (hereinafter referred to as "embodiments") will be described with reference to the drawings as appropriate. The drawings referred to in the following description schematically show the embodiments, so the scale, interval, positional relationship, etc. of each member may be exaggerated, or part of the member may be omitted from the illustration. Further, the present invention is not limited to the embodiments taken up here, and combinations and improvements can be made as appropriate without changing the gist.

[0015] ≪First Embodiment≫ The configuration of the radiation monitor 1 according to the first embodiment of the present invention will be described with reference to the drawings. FIGS. 1A and 1B are diagrams showing a schematic configuration example of the radiation monitor 1 according to the first embodiment of the present invention. Note that FIG. 1A is a view seen from the lateral direction in which the radiation detection unit 2 and the photon transmission unit 7 described later are arranged side by side. FIG. 1B is a view seen in the front direction from the left side of the paper surface of the radiation detection unit 2 in FIG. 1A.

[0016] In FIG. 1A, the radiation monitor 1 includes a radiation detection unit 2 and a photon transmission unit 7. The radiation detection unit 2 includes a first phosphor 4, a second phosphor 5, and a photon reflection layer 6. The radiation detected by the radiation monitor 1 is based on the radiation that principally enters from the direction described as the reference irradiation direction 3. Examples of the radiation that can be measured by the radiation monitor 1 include electromagnetic waves such as X-rays and γ-rays, and particle rays such as α-rays, β-rays, and neutron rays.

[0017] As shown in FIG. 1A, the radiation detection unit 2 is an element having a first phosphor 4 that emits light with an intensity corresponding to the dose rate of the incident radiation, a second phosphor 5, and a photon reflection layer 6 that reflects photons emitted from the phosphor. As shown in FIG. 1B, when the radiation detection unit 2 in FIG. 1A is viewed from the front direction from the left side in the plane of the paper, it is configured in a rectangular (square or rectangle) shape. In FIGS. 1A and 1B, the first phosphor 4 and the second phosphor 5 have a structure in which they are arranged adjacent to each other in parallel. The photon reflection layer 6 has a structure arranged between the first phosphor 4 and the second phosphor 5. Details of the configuration and function of the radiation detection unit 2 will be described later, but the outline is as follows.

[0018] <Overview of Radiation Detection Unit 2> As shown in FIG. 1A, in the radiation detection unit 2, a part of the radiation input to the first phosphor 4 reacts with the phosphor, and a part of the photons emitted from the phosphor reaches the photon transmission unit 7. In addition, the radiation that was input to the first phosphor 4 but did not react with the phosphor passes through the photon reflection layer 6 and goes toward the second phosphor 5. In the second phosphor 5, the radiation reacts with the phosphor, and a part of the photons emitted from the phosphor reaches the photon transmission unit 7. In addition, the photon reflection layer 6 functions so as not to return the photons generated in the second phosphor 5 to the first phosphor 4. Also, the photon reflection layer 6 functions so that the photons generated in the first phosphor 4 do not enter the second phosphor 5. Note that the photon reflection layer 6 reflects photons but transmits radiation.

[0019] <Details of Radiation Detection Unit 2> The "first phosphor 4 and second phosphor 5" and "photon reflection layer 6" in the radiation detection unit 2 will be described in detail.

[0020] 《First Phosphor 4 and Second Phosphor 5》 The first phosphor 4 and the second phosphor 5 are composed of a composition that exhibits luminescence (luminescence, cold light). As long as it is a composition that exhibits the phenomenon and action of luminescence, the object and material of the fluorescence phenomenon are not particularly limited. For example, there are photoluminescence by light such as ultraviolet light, radioluminescence by radiation, cathodoluminescence by an electron beam, electroluminescence by an electric field, chemiluminescence by a chemical reaction, and the like.

[0021] Specifically, the first phosphor 4 and the second phosphor 5 are, for example, NaI, CsI, LiI, SrI as a base material 2 , Bi 4 , Ge 3 , O 12 , Bi 4 , Si 3 , O 12 , CdWO 4 , PbWO 4 , ZnS, CaF 2 , LuAG, LuAP, Lu 2 , O 3 , Y 3 , Al 5 , O 12 , YAlO 3 , Lu 2 , SiO 5 , LYSO, Y 2 , SiO 5 , Gd 2 , SiO 5 , BaF 2 , CeF 3 , CeBr 3 , CsF, LiF, Gd 2 , O 2 , S, LaBr 3 , CeBr 3 , Gd 3 , Al 2 , Ga 3 , O 12 , Cs 2 , LiYCl 6 , Cs 2 , HfI 6 , ScTaO 4 , LaTaO 4 , LuTaO 4 , GdTaO 4 , YTaO 4 , and light-transmissive materials such as sialon phosphors (a general term for Si-Al-O-N substances) and the like.

[0022] Alternatively, among these light-transmissive materials, there are light-transmissive materials containing rare earth elements such as La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Y, or elements such as Tl, Na, Ag, W, CO 3 and powdery fluorescent materials.

[0023] In addition, the valence of the elemental ions contained in the first phosphor 4 and the second phosphor 5 is not particularly limited as long as it can be used for light emission. For example, monovalent, divalent, trivalent, tetravalent, etc. can be used.

[0024] The manufacturing method of the first phosphor 4 and the second phosphor 5 is not particularly limited as long as a luminescent composition can be grown. For example, the floating zone method, the Czochralski method (pulling method), the micro-pulling method, the Bridgman method, the Verneuil method, etc. can be adopted.

[0025] 《Photon Reflective Layer 6》 The photon reflective layer 6 is preferably sandwiched between the first phosphor 4 and the second phosphor 5. With this sandwiched structure, photons generated by the first phosphor 4 can be transmitted to the photon transmission part 7 without passing through the second phosphor 5. Also, with the above structure, photons generated by the second phosphor 5 can be transmitted to the photon transmission part 7 without passing through the first phosphor 4.

[0026] The composition and structure of the photon reflective layer 6 are not particularly limited as long as it can reflect photons generated inside the phosphor. For example, tapes made of fluororesins such as Teflon (registered trademark), aluminum foils, barium sulfate, optical films, optical filters, thin films, multilayer films, phosphors, greases, powders, paints, air, bulk metals, etc. can be used. The bulk metal is composed of, for example, a metal with a thickness of less than 1 mm and thicker than the above-mentioned aluminum foil. In addition, the surface states of the first phosphor 4 and the second phosphor 5 can be utilized as the photon reflection layer 6. For example, a structure obtained by performing surface processing or the like on the outer surfaces of the first phosphor 4 and the second phosphor 5 can be adopted as the photon reflection layer. In addition, examples of applicable surface processing methods include machining such as polishing, sputtering, vapor deposition, film formation by plating or coating, heat treatment, chemical treatment, painting, and the like.

[0027] The refractive index of the photon reflection layer 6 is not particularly limited as long as it can reflect photons. For example, by using a material with a refractive index smaller than that of the first phosphor 4 (the second phosphor 5) for the photon reflection layer 6, the reflection probability of photons generated by the first phosphor 4 (the second phosphor 5) can be improved. Also, it is possible to effectively suppress the sensitivity to low-energy radiation.

[0028] <Other matters related to the radiation detection unit 2> As other matters related to the radiation detection unit 2, "housing" and "reference irradiation direction" will be described below.

[0029] 《Housing》 Although not shown in FIG. 1A, the radiation monitor 1 houses the radiation detection unit 2 (the first phosphor 4, the second phosphor 5, and the photon reflection layer 6) in a housing (a protective container, an outer shell container). The radiation detection unit 2 is preferably shielded from light by the housing in order to distinguish external light from the light from the first phosphor 4 and the second phosphor 5. The housing is a container for housing the radiation detection unit. The material constituting the housing is not particularly limited as long as it can reflect light. For example, Teflon tape, barium sulfate, aluminum, stainless steel, or the like can be adopted.

[0030] 《Reference irradiation direction 3》 In FIG. 1A, the reference irradiation direction 3 represents an example of the reference (0° direction) of the incident direction of the radiation to be measured by the radiation monitor 1. The characteristics and performance of the radiation monitor 1 are determined with respect to the radiation from this reference irradiation direction 3. However, even if the radiation comes from a direction other than the reference irradiation direction 3, although there are differences and changes in the characteristics and performance, the radiation monitor 1 still functions. The reference irradiation direction 3 is preferably perpendicular to the axial direction (transmission direction) of the first phosphor 4, the second phosphor 5, the photon reflection layer 6, and the photon transmission unit 7.

[0031] <Photon transmission unit 7> The photon transmission unit 7 in FIG. 1A will be described. As shown in FIG. 1A, the photon transmission unit 7 is connected to the first phosphor 4, the second phosphor 5, and the photon reflection layer 6. And it transmits the light emitted from the radiation detection unit 2. The photon transmission unit 7 is connected to a photodetector 8 described later (FIG. 2). The photon transmission unit 7 is not particularly limited as long as it can transmit photons. For example, an optical fiber, an optical guide, an optical pipe, etc. can be adopted. Moreover, examples of the material constituting the photon transmission unit 7 include quartz, plastic, etc.

[0032] <Supplementary explanation of terms> Hereinafter, a supplementary explanation will be given first about the meaning of the terms used in the description of radiation, photons, and analysis equipment. In the following description of this specification, the "counting rate of the electrical pulse signal" means the number of electrical pulse signals measured per unit time. Moreover, the "predetermined standard range" indicates the counting rate range of photons and represents the range defined in each standard. Moreover, the "wavelength within a predetermined range" indicates the transmissible wavelength range. Note that photons are controlled by transmitting only photons of a specific wavelength. Moreover, the "single photon" refers to each individual photon generated inside the phosphor by the incidence of radiation.

[0033] <Block diagram of the radiation monitor and related equipment> Next, the radiation monitor and related equipment will be described. FIG. 2 is a block diagram showing a configuration example of the radiation monitor 1 and related equipment according to the first embodiment. In FIG. 2, a radiation monitor 1 including a radiation detection unit 2 and a photon transmission unit 7 further includes a photodetector 8, a counter 9, and an analysis / display device 10 to constitute a radiation monitor 1B.

[0034] In FIG. 2, the photodetector 8 is a detector (photodetector) connected to the photon transmission unit 7 that converts photons transmitted from the photon transmission unit 7 into an electrical pulse signal. As the photodetector 8, for example, a photomultiplier tube, an avalanche photodiode, or the like can be employed. By using a photomultiplier tube or the like as the photodetector 8, a single photon can be detected as one current pulse signal with amplified current.

[0035] The counter 9 is a device connected to the photodetector 8 that counts the electrical pulse signals input from the photodetector 8. As the counter 9, for example, a digital signal processor can be employed.

[0036] The analysis / display device 10 is a device connected to the counter 9 that converts (analyzes) the count rate of the electrical pulse signals counted by the counter 9 into a radiation dose rate and displays the value. The analysis / display device 10 includes a storage device (not shown) having a database that associates the count rate of the electrical pulse signals with the radiation dose rate, an arithmetic device (not shown) that converts the radiation dose rate from the count rate of the electrical pulse signals using the database, and a display device (not shown) that displays the converted radiation dose rate. As the analysis / display device 10, for example, a personal computer having the above-described functions (storage, arithmetic, display) can be employed.

[0037] In the radiation monitor 1 (1B) according to the first embodiment of the present invention, for example, due to the incidence of γ-rays, the radiation dose rate is converted from the count rate of single photons included in a plurality of photons generated by the first phosphor 4 and the second phosphor 5. The method of the radiation monitor 1 (1B) according to the first embodiment of the present invention is different from the conventional method of converting the radiation dose rate from the γ-ray count rate.

[0038] <Relationship between radiation dose rate and single photon count rate> FIG. 3 is a diagram showing a schematic example of the relationship between the radiation dose rate and the single photon count rate. In FIG. 3, the horizontal axis represents the "radiation dose rate", and the vertical axis represents the "photon count rate (single photon count rate)". As shown in FIG. 3, if the count rate of this single photon can be measured, the radiation dose rate can be obtained. Therefore, the radiation dose rate can be converted from the count rate of single photons calculated using the relationship in FIG. 3.

[0039] <Generation of light when radiation is incident on the phosphor> Next, the operation of the radiation detection unit 2 in the radiation monitor 1 will be described. FIG. 4 is a diagram showing a schematic example of the generation of light when the radiation 11 is incident on the radiation detection unit 2. In FIG. 4, when the radiation 11 is incident on the radiation detection unit 2, an interaction 12 occurs in the phosphor (4, 5: FIG. 1) provided in the radiation detection unit 2. Along with this interaction 12, a plurality of single photons 13 are generated.

[0040] <Comparison between the conventional example and the present embodiment example in the electrical pulse signal for measuring the output of the photodetector> FIG. 5 is a diagram showing a schematic example of comparing the electrical pulse signal 15 when it is assumed that the output of the photodetector 8 of the present embodiment is measured and the electrical pulse signal 14 when the output of the photodetector 8 is measured by a conventional measuring device. In FIG. 5, the horizontal axis represents "time", and the vertical axis represents "voltage". In FIG. 5, when the output of the photodetector (8) is measured by the measuring device of the conventional example, the electrical pulse signal 14 is, conventionally, usually generated with a plurality of single photons 13 when one radiation 11 (FIG. 4) enters the radiation detection unit (2), and is measured as one electrical pulse signal 14 using the photodetector (8). That is, in the photodetector of the measuring device of the conventional example, instead of detecting a pulse of a single photon, a set of a plurality of pulses is collectively measured and captured as the waveform of an electrical signal.

[0041] On the other hand, in the present embodiment, each single photon 13 transmitted from the photon transmission unit 7 (FIGS. 1 and 2) is measured by the photodetector 8 (FIG. 2). As shown in FIG. 5, the single photon 13 is measured as an electrical pulse signal 15 having a time width of about 2 ns by the photodetector 8 (FIG. 2). Note that the time width of about 2 ns depends on the performance of the photodetector 8. Then, the counter 9 shown in FIG. 2 counts (measures) the number of single photons 13 with each electrical pulse signal 15 (FIG. 5) for each emission.

[0042] That is, in the measuring device of the conventional example, a plurality of single photons 13 (FIG. 4) generated by the input of radiation are collectively measured by the photodetector (8) as an electrical pulse signal 14 (FIG. 5) as a waveform. In contrast, in the present embodiment, each single photon 13 is measured by the photodetector 8 (FIG. 2) as an electrical pulse signal 15 (FIG. 5) having a time width of about 2 ns. In this way, in order to measure and count each single photon 13 as each electrical pulse signal, it also depends on the performance of the photodetector 8 (FIG. 2) and the characteristics of the time constant during the reaction as a phosphor of the first phosphor 4 and the second phosphor 5.

[0043] Also, when adopting the method of collectively measuring with the electrical pulse signal 14 (FIG. 5) as a waveform by the conventional photodetector (8), the characteristics of the phosphor are also involved. When detecting in a batch as a waveform with the electrical pulse signal 14 in FIG. 5, generally in the fluorescence reaction, a fluorescent substance made of a material with a short time constant is adopted, and a plurality of generated photons are measured in a batch, so that it is generally detected as a waveform signal. When this fluorescent substance made of a material with a short time constant is used as a photodetector, it may not be able to withstand a high temperature of about 300 °C or a high-radiation environment. Conversely, even if there is a fluorescent substance that can withstand a high temperature or a high-radiation environment, due to the large (long) time constant during the reaction, it may not be adopted by conventional photodetectors.

[0044] On the other hand, when measuring the phosphor in FIG. 5 as an electrical pulse signal 15 (FIG. 5) with a time width of about 2 ns for each single photon 13 shown in FIG. 5 by the photodetector 8 (FIG. 2), a phosphor with a long time constant during the reaction is adopted. A method of detecting in pulses is used while this reaction lasts for a long time. Some of the phosphors with a long time constant during the reaction of this phosphor were not adopted by the conventional measurement methods for the reasons described above. On the other hand, in this embodiment, by the method of measuring each single photon 13 as each electrical pulse signal, a phosphor with a long time constant during the reaction of the phosphor can be adopted.

[0045] Therefore, there is a possibility that phosphors having useful characteristics under high-temperature and high-radioactivity conditions that were not adopted conventionally can also be adopted. That is, the radiation monitor 1 of this embodiment may be adopted even in a high-temperature and high-radioactivity environment, and the range of selection of the fluorescent substance is widened. As a result, there is a possibility of realizing a radiation monitor that can withstand even a high-temperature and high-radioactivity environment. Moreover, since it is a method of detecting in pulses, it is a measurement method that can be measured at high speed, the measurement sensitivity is increased, and the measurement range may be expanded.

[0046] <Radiation energy dependence of photon counting rate> FIG. 6 is a schematic diagram showing an example of the radiation energy dependence of the photon counting rate. In FIG. 6, the horizontal axis represents "radiation energy" and the vertical axis represents "photon counting rate". Note that the "photon counting rate" is the ratio at which radiation is converted into photons and measured by the counter 9 (FIG. 1) when the radiation passes through the phosphor.

[0047] As shown in FIG. 6, the photon counting rate detected by the photodetector 8 changes depending on the energy of the incident radiation. Generally, as the radiation energy decreases, the photon counting rate increases, and as the radiation energy increases, the photon counting rate decreases. The reason for this is that depending on the energy of the incident radiation, the phosphors included in the radiation detection unit 2 have different measurement sensitivities. However, the wavelength of the photons generated from the phosphor is not related to the level of the radiation energy and becomes a predetermined value depending on the characteristics of the phosphor material.

[0048] The phosphors (the first phosphor 4 and the second phosphor 5) are more likely to capture and react with low-energy radiation. Or, they are more likely to be imparted with energy from the radiation. Conversely, high-energy radiation is more likely to pass through the phosphor. The phosphor imparted with energy generates photons. As described above, this interaction that generates a single photon in response to the radiation is more likely to occur with lower-energy radiation. Particularly when a phosphor with a high density is applied to the radiation detection unit 2, this tendency for the interaction to occur more easily with lower-energy radiation becomes prominent.

[0049] However, the dose rate measurement of the radiation monitor is used in an environment where various energies of radiation are mixed. Therefore, it is necessary to flatten the sensitivity of the radiation detection unit 2 so that the measured photon counting rate falls within a predetermined standard range 31 as shown in FIG. 6, for example, for various radiation energies. Specific measures for this flattening will be described later.

[0050] <Thickness Dependence of Phosphor's Energy Implantation Ratio> FIG. 7 is a diagram showing a schematic relationship example regarding the thickness dependence of the phosphor's energy implantation ratio. Note that the energy implantation ratio is the ratio of the energy that is implanted as the phosphor's energy into the phosphor when radiation passes through the phosphor out of the radiation energy. In FIG. 7, the horizontal axis represents "thickness of the phosphor", and the vertical axis represents "energy implantation ratio". Also, the characteristic with low radiation energy is indicated by low-energy radiation 32, and the characteristic with high radiation energy is indicated by high-energy radiation 33.

[0051] As shown in FIG. 7, since the low-energy radiation 32 has weak radiation penetration power, the main energy of the radiation is implanted near the surface of the phosphor on the radiation incident surface. On the other hand, the high-energy radiation 33 has strong radiation penetration power, and energy is implanted deeper into the phosphor in the thickness direction compared to the low-energy radiation 32. Note that the "energy implantation ratio" in FIG. 7 corresponds to the "ratio" of whether the implanted energy reacts on the surface of the phosphor or reaches deeper inside the phosphor, and does not represent the "implanted energy" itself.

[0052] <Generation of Light When Radiation Incides on the First Phosphor and the Second Phosphor> FIG. 8 is a diagram showing a schematic example regarding the generation of light when radiation incides on the first phosphor 4 and the second phosphor 5. As shown in FIG. 8, when the low-energy radiation 32 incides on the radiation detection unit 2, interaction 12 occurs in the first phosphor 4, and the generated photons 40 are transmitted to the photon transmission unit 7 through the region S1 where the first phosphor 4 and the photon transmission unit 7 are in contact. Note that the photons 40 are not necessarily single photons (13: FIG. 4).

[0053] Also, since the high-energy radiation 33 has high radiation energy, it reaches the deeper part (the second phosphor 5) inside the radiation detection unit 2. When high-energy radiation 33 enters the radiation detection unit 2, an interaction 12 occurs in the second phosphor 5, and the generated photons 40 are transmitted to the photon transmission unit 7 through the region S2 where the second phosphor 5 and the photon transmission unit 7 are in contact with each other. In these reactions, the photon reflection layer 6 serves to prevent the photons 40 generated in the first phosphor 4 from passing through to the second phosphor 5, and also to prevent the photons 40 generated in the second phosphor 5 from passing through to the first phosphor 4. Note that the photon reflection layer 6 is made of a material with a lower refractive index of light compared to the first phosphor 4 and the second phosphor 5.

[0054] Also, the number of photons 40 generated by the first phosphor 4 and the second phosphor 5 and transmitted to the photon transmission unit 7 is proportional to the contact area between the phosphor and the photon transmission unit 7. Let the contact area between the first phosphor 4 and the photon transmission unit 7 be "SS1", and the contact area between the second phosphor 5 and the photon transmission unit 7 be "SS2". Therefore, by adjusting the contact area ratio (SS1:SS2) between the photon transmission unit 7, the first phosphor 4, and the second phosphor 5, the sensitivity to low-energy radiation 32 and high-energy radiation 33 can be adjusted.

[0055] In this way, the radiation monitor 1 has a structure in which the first phosphor 4 and the second phosphor 5 are arranged adjacent to each other in parallel, a photon reflection layer 6 is provided between the first phosphor 4 and the second phosphor 5, and the first phosphor 4, the photon reflection layer 6, and the second phosphor 5 are in contact with the photon transmission unit 7. In this structure, by selecting an appropriate configuration for each contact area ratio (SS1:SS2), the energy characteristics of the sensitivity of the radiation detection unit 2 can be flattened.

[0056] Note that in FIG. 8, for the sake of explanation, the situation where high-energy radiation 33 interacts with the first phosphor 4 to generate single photons is omitted from the description. As in the relationship between the "phosphor thickness" and the "applied energy ratio" shown in FIG. 7, even in the high-energy radiation 33, the generation of photons due to the interaction in the first phosphor 4 is more frequent than the generation of photons due to the interaction in the second phosphor 5. That is, the generation of photons due to the interaction in the first phosphor 4 is frequent not only in the low-energy radiation 32 but also in the high-energy radiation 33. For this reason too, in order to flatten the energy characteristics of the sensitivity of the radiation detection unit 2, it is necessary to adjust so that the contact area SS1 between the first phosphor 4 and the photon transmission unit 7 is smaller than the contact area SS2 between the second phosphor 5 and the photon transmission unit 7.

[0057] <Effect of the First Embodiment> According to the first embodiment of the present invention, it is possible to provide a radiation monitor that can flatten the energy characteristics of the sensitivity to emit photons with respect to incident radiation with a small and single radiation detection unit.

[0058] ≪Second Embodiment≫ The configuration of the radiation monitor 1C according to the second embodiment of the present invention will be described with reference to FIGS. 9A and 9B. FIGS. 9A and 9B are diagrams showing a schematic configuration example of the radiation monitor 1C according to the second embodiment of the present invention. Note that FIG. 9A is a view seen from the lateral direction in which the radiation detection unit 2C and the photon transmission unit 7 are arranged side by side. Further, FIG. 9B is a view seen with the radiation detection unit 2C in FIG. 9A as the front direction from the left side in the plane of the paper.

[0059] In FIG. 9A, the radiation monitor 1C is configured to include a radiation detection unit 2C and a photon transmission unit 7. Further, the radiation detection unit 2C is configured to include a first phosphor 4C, a second phosphor 5C, and a photon reflection layer 6C. Although the configuration of the radiation monitor 1C in Fig. 9A is different from that of the radiation detection unit 2C, it appears to be the same as the configuration of the radiation monitor 1 in Fig. 1A. Therefore, overlapping explanations will be omitted. The differences between the configuration of the radiation detection unit 2C in Figs. 9A and 9B and the configuration of the radiation detection unit 2 in Figs. 1A and 1B will be described with reference to Fig. 9B.

[0060] In Fig. 9B, the difference from Fig. 1B is that while Fig. 1B shows the radiation detection unit 2 configured in a square (square or rectangle) shape when viewed from the front direction, in Fig. 9B, the radiation detection unit 2C (the first phosphor 4C, the second phosphor 5C, and the photon reflection layer 6C) is configured in a circular shape when viewed from the front direction. That is, when Figs. 9A and 9B are combined, the radiation detection unit 2C of the radiation monitor 1C according to the second embodiment of the present invention has a cylindrical shape. Therefore, in Fig. 9B, even if the relative relationship between the radiation detection unit 2C and the reference irradiation direction 3 varies in the circumferential direction, the change in characteristics is smaller than the change in the angle of the reference irradiation direction 3 in Fig. 1B.

[0061] <Effect of the Second Embodiment> According to the second embodiment of the present invention, even if the relative relationship between the radiation detection unit 2C and the reference irradiation direction 3 varies in the circumferential direction in Fig. 9B, the change in characteristics is smaller than the change in the angle of the reference irradiation direction 3 in Fig. 1B.

[0062] ≪Third Embodiment≫ The configuration of the radiation monitor 1D according to the third embodiment of the present invention will be described with reference to Fig. 10. Fig. 10 is a view showing a schematic configuration example of the radiation monitor 1D according to the third embodiment of the present invention from the lateral direction in which the radiation detection unit 2D and the photon transmission unit 7 are arranged side by side. In Fig. 10, the radiation monitor 1D is configured to include a radiation detection unit 2D and a photon transmission unit 7. The radiation detection unit 2D includes a first phosphor 4D, a second phosphor 5D, and a photon reflection layer 6D. Further, the reference irradiation direction 3 is perpendicular to the first phosphor 4D, the second phosphor 5D, and the photon reflection layer 6D.

[0063] In FIG. 10, the second phosphor 5D has a hemispherical shape. Further, the photon reflection layer 6D has the shape of a hemispherical outer shell so as to cover the second phosphor 5D. Furthermore, the first phosphor 4D has the shape of a thick hemispherical outer shell so as to cover the photon reflection layer 6D. Therefore, the radiation detection unit 2D composed of the first phosphor 4D, the photon reflection layer 6D, and the second phosphor 5D is configured in a spherical shape (hemispherical shape) that is half of a sphere as a whole. However, it is simply referred to as a spherical shape. Further, the photon transmission unit 7 is in contact with each of the first phosphor 4D, the photon reflection layer 6D, and the second phosphor 5D that constitute the radiation detection unit 2D.

[0064] As described above, the radiation monitor 1D according to the second embodiment has the same configuration in terms of phase geometry in the relationship between the radiation monitor 1 according to the first embodiment, the radiation detection unit (2, 2D), and the photon transmission unit 7, but the shape of the radiation detection unit 2D is different in that it has a hemispherical shape. Also, the reference irradiation direction 3 is different in that it is the center of the hemispherical-shaped radiation detection unit 2D. In this way, since the radiation detection unit 2D has a spherical phosphor and a photon reflection layer, even if the relative relationship with the reference irradiation direction 3 changes, it is easy to take in radiation into the radiation detection unit 2D, so it is possible to improve the direction characteristics of the radiation.

[0065] <Effect of the Third Embodiment> According to the third embodiment of the present invention, since the radiation detection unit 2D has a spherical phosphor and a photon reflection layer, there is an effect that it is possible to improve the direction characteristics of the radiation.

[0066] ≪Fourth Embodiment≫ The configuration of the radiation monitor 1E according to the fourth embodiment of the present invention will be described with reference to FIG. 11. FIG. 11 is a diagram showing a schematic configuration example of the radiation monitor 1E according to the fourth embodiment of the present invention from the lateral direction in which the radiation detection unit 2D and the photon transmission units 7E1 and 7E2 are arranged side by side. In FIG. 11, the radiation detection unit 2D in the radiation monitor 1E includes a first phosphor 4D, a second phosphor 5D, and a photon reflection layer 6D. However, since the radiation detection unit 2D, the first phosphor 4D, the second phosphor 5D, and the photon reflection layer 6D have substantially the same configurations as the radiation detection unit 2D, the first phosphor 4D, the second phosphor 5D, and the photon reflection layer 6D shown in FIG. 10 showing the third embodiment, respectively, duplicate explanations are omitted.

[0067] The difference between the radiation monitor 1E in FIG. 11 and the radiation monitor 1D in FIG. 10 is that the photon transmission unit is configured to be divided into a photon transmission unit 7E1 and a photon transmission unit 7E2. In FIG. 11, since there is a gap between the photon transmission unit 7E1 and the photon transmission unit 7E2, a part of the photons output from the second phosphor 5D may pass through the gap between the photon transmission unit 7E1 and the photon transmission unit 7E2. The photons passing through or leaking through this gap will not be counted. That is, the count rate of the photons output from the second phosphor 5D will decrease.

[0068] Thus, with a configuration having two or more photon transmission units (7E1, 7E2), it becomes easy to adjust the contact area ratio among the photon transmission unit (7), the first phosphor 4D, and the second phosphor 5D, and it becomes possible to more effectively flatten the energy characteristics of the sensitivity of the radiation detection unit 2D.

[0069] In FIG. 11, there are various methods for handling the separated photon transmission units of the photon transmission unit 7E1 and the photon transmission unit 7E2. For example, there are the following methods. <1> Bundle the photon transmission unit 7E1 and the photon transmission unit 7E2 and put them into the photodetector 8 (FIG. 1B). <2> Input them into an optical fiber coupler and combine them into one fiber. <3> Input it into the photodetector 8 (FIG. 1B) using a light collecting lens.

[0070] <Effect of the Fourth Embodiment> According to the fourth embodiment of the present invention, the radiation monitor 1E has the first phosphor 4D, the second phosphor 5D, and the photon reflection layer 6D, and by having two or more photon transmission parts (7E1, 7E2), it is possible to flatten the sensitivity to radiation of various energies and improve the measurement accuracy of the dose rate.

[0071] ≪Fifth Embodiment≫ The configuration of the radiation monitor 1F according to the fifth embodiment of the present invention will be described with reference to FIG. 12. FIG. 12 is a view showing a schematic configuration example of the radiation monitor 1F according to the fifth embodiment of the present invention from the lateral direction in which the radiation detection part 2F and the photon transmission part 7 are arranged side by side. In FIG. 12, what is different from FIG. 1 is the configuration of the radiation detection part 2F. Since the other configurations are generally the same as those in FIG. 1, duplicate explanations will be omitted as appropriate.

[0072] In FIG. 12, the radiation detection part 2F is configured to include a first phosphor 4F, a second phosphor 5, a third phosphor 16, a photon reflection layer 6, and a second photon reflection layer 17. Compared with FIG. 1, the new components in FIG. 12 are that the third phosphor 16 and the second photon reflection layer 17 are provided. However, due to the provision of the third phosphor 16, the proportion occupied by the first phosphor 4F has relatively decreased.

[0073] The third phosphor 16 and the second photon reflection layer 17 are arranged adjacent to each other in parallel. Therefore, the photons generated by the radiation incident on the third phosphor 16 are reflected by the second photon reflection layer 17 and do not reach the photon transmission part 7. Thus, the radiation monitor 1F in FIG. 12 has the third phosphor 16 and the second photon reflection layer 17, so that the sensitive volume of the first phosphor 4F can be reduced. However, the second phosphor 5 interacts 12 (FIG. 8) with the high-energy radiation 33 (FIGS. 7 and 8) that passes through the first phosphor 4F and the third phosphor 16, generating photons 40 (FIG. 8). Therefore, while maintaining the count rate of the high-energy radiation 33 (FIGS. 7 and 8), the count rate for the low-energy radiation 32 (FIGS. 7 and 8) with increased sensitivity can be suppressed, enabling further flattening of the energy characteristics of the sensitivity of the radiation detection unit 2F (FIG. 12).

[0074] In FIG. 12, it is important that the third phosphor 16 and the second photon reflection layer 17 have a structure in which they are adjacent to each other and arranged in parallel. Also, the third phosphor 16 is not particularly limited as long as it is a material capable of absorbing radiation. For example, phosphors, metals, resins, etc. can be used. The second photon reflection layer 17 is not particularly limited as long as it can reflect photons generated inside the phosphor. For example, Teflon tape, aluminum foil, barium sulfate, optical films, optical filters, thin films, multilayer films, phosphors, greases, powders, paints, air, bulk metals, etc. can be utilized.

[0075] <Effects of the Fifth Embodiment> According to the fifth embodiment of the present invention, the radiation monitor 1F has a structure in which the third phosphor 16 and the second photon reflection layer 17 are adjacent to each other and arranged in parallel, so that the sensitivity can be flattened for radiations of various energies, and there is an effect of improving the measurement accuracy of the dose rate.

[0076] ≪Sixth Embodiment≫ The configuration of the radiation monitor 1G according to the sixth embodiment of the present invention will be described with reference to FIG. 13. FIG. 13 is a view showing a schematic configuration example of the radiation monitor 1G according to the sixth embodiment of the present invention from the lateral direction in which the radiation detection unit 2G and the photon transmission unit 7 are arranged side by side. In FIG. 13, what is different from FIG. 1 is the configuration of the radiation detection unit 2G. Since the other configurations are generally the same as those in FIG. 1, duplicate explanations will be omitted as appropriate.

[0077] In FIG. 13, the radiation detection unit 2G includes a first phosphor 4G, a second phosphor 5, a photon reflection layer 6, and a photon absorption layer 18. Compared with FIG. 1, the new component in FIG. 13 is that the photon absorption layer 18 is provided. The photon absorption layer 18 is connected to the first phosphor 4G, the photon reflection layer 6, and the photon transmission unit 7. The photon absorption layer 18 attenuates the number of passing photons. Alternatively, it has a function of transmitting wavelengths within a predetermined range. By this function, the number of photons transmitted from the first phosphor 4G to the photon transmission unit 7 can be reduced, the counting rate for low-energy radiation 32 with increased sensitivity can be suppressed, and the energy characteristics of the sensitivity of the radiation detection unit 2G can be flattened.

[0078] Note that the material of the photon absorption layer 18 is not particularly limited as long as it has a function of attenuating the number of photons or transmitting wavelengths within a predetermined range for the photons transmitted from the first phosphor 4G. For example, an optical film, an optical filter, a thin film, a multilayer film, a phosphor, grease, powder, paint, air, etc. can be applied.

[0079] <Effect of the Sixth Embodiment> According to the sixth embodiment of the present invention, the radiation monitor 1G has a function of attenuating the number of photons or transmitting wavelengths within a predetermined range by the photon absorption layer 18, so that the sensitivity can be flattened for radiations of various energies, and there is an effect of improving the measurement accuracy of the dose rate.

[0080] <Preferred Usage Example of Radiation Monitor> Next, a preferred usage example of the radiation monitor (1, 1B, 1C, 1D, 1E, 1F, 1G) of the present invention will be described. FIG. 14 is a block diagram showing an outline of a usage example in a radiation environment which is an actual measurement target of the radiation monitor 1 in FIG. 1 or FIG. 2, for example. In FIG. 14, the radiation detection unit 2 is installed in the measurement target area 34. Also, a photodetector 8 connected to the photon transmission unit 7, a counter 9, and an analysis / display device 10 are installed in the general area 35.

[0081] With these configurations, it is possible to measure, with high precision, the dose rate with respect to the energies of various radiations corresponding to the measurement target area 34, for example, inside a reactor building or inside a reactor containment vessel, in the general area 35 where the influence of radiation is small. Furthermore, for example, in radiation measurements in nuclear power plants, nuclear fuel reprocessing facilities, medical facilities using radioactive isotopes, industrial facilities, research accelerator facilities, general environmental monitoring devices, etc., the radiation monitors (1, 1B, 1C, 1D, 1E, 1F, 1G) of the present invention can be applied.

[0082] Note that in FIG. 14, since the reference irradiation direction 3 does not necessarily coincide with the directions of radiations coming from various locations in the measurement target area 34, various contrivances may be required for the measurement accuracy and measurement method. For example, if the radiation monitor 1D provided with the hemispherical radiation detection unit 2D shown in FIG. 10 is used, the direction characteristics of the radiation may be improved and the measurement accuracy may be enhanced.

[0083] ≪Other Embodiments≫ Note that the present invention is not limited to the embodiments described above, and further includes various modifications. For example, the above-described embodiments have been described in detail for the purpose of explaining the present invention clearly, and are not necessarily limited to those having all the configurations described. Also, a part of the configuration of one embodiment can be replaced with a part of the configuration of another embodiment, and furthermore, a part or all of the configuration of another embodiment can be added to, deleted from, or replaced with the configuration of one embodiment. Other embodiments and modifications will be further described below.

[0084] Structure of the First Phosphor, Second Phosphor, and Photon Reflection Layer In FIGS. 1A and 1B, one case of each of the first phosphor 4, the second phosphor 5, and the photon reflection layer 6 is shown. However, the number of the first phosphor 4, the second phosphor 5, and the photon reflection layer 6 is not particularly limited as long as they have a structure arranged adjacent to each other. It is also possible to stack two or more phosphors and reflection layers. The shapes of the first phosphor 4, the second phosphor 5, and the photon reflection layer 6 are not particularly limited as long as they have a structure arranged adjacent to each other. Specifically, as described above in part, shapes such as a cube, a rectangular parallelepiped, a prism, a cylinder, and a hemisphere can be used.

[0085] Plural Photon Transmission Parts In FIG. 11, two photon transmission parts 7E1 and 7E2 are described, but it may be composed of three or more photon transmission parts. Also, in the plural photon transmission parts, the contact areas with the radiation detection part (2D) may be different from each other.

[0086] The Third Phosphor, the Second Photon Reflection Layer In FIG. 12, it is important that the third phosphor 16 and the second photon reflection layer 17 have a structure arranged adjacent to each other in parallel. For example, the number of the third phosphor 16 and the second photon reflection layer 17 is not particularly limited as long as they have a structure arranged adjacent to each other, and it is also possible to stack two or more phosphors and reflection layers.

[0087] Materials of the First Phosphor and the Second Phosphor In the description of the radiation detection part 2 of the radiation monitor 1 of the first embodiment with reference to FIG. 1, the compositions of the first phosphor 4 and the second phosphor 5 were described as the same composition. However, the first phosphor 4 and the second phosphor 5 may have different compositions. By using a composition for the second phosphor 5 that is more likely to react to high-energy radiation than the first phosphor 4, there is a further effect of flattening the energy characteristics. Explanation of Reference Numerals

[0088] 1, 1B, 1C, 1D, 1E, 1F, 1G Radiation monitor 2, 2C, 2D, 2F, 2G Radiation detection unit 3 Reference irradiation direction 4, 4C, 4D, 4F, 4G First phosphor 5, 5C, 5D Second phosphor 6, 6C, 6D Photon reflection layer 7, 7E1, 7E2 Photon transmission unit 8 Photodetector 9 Counter 10 Analysis and display device 11 Radiation 12 Interaction 13 Single photon (photon) 16 Third phosphor 17 Second photon reflection layer (photon reflection layer) 18 Photon absorption layer 30 Reference count rate 31 Specification range 32 Low - energy radiation (radiation) 33 High - energy radiation (radiation) 34 Measurement target area 35 General area 40 Photon

Claims

1. A radiation detection unit having a phosphor that emits photons in response to incident radiation, A photon transmission unit that transmits photons emitted from the phosphor of the radiation detection unit, Comprising, The phosphor has a first phosphor and a second phosphor, The first phosphor and the second phosphor are adjacent to each other and arranged in parallel, There is a photon reflection layer between the first phosphor and the second phosphor, The first phosphor, the photon reflection layer, and the second phosphor are in contact with the photon transmission unit, The radiation detection unit is configured with a structure in which radiation is incident in the order of the first phosphor, the photon reflection layer, and the second phosphor, The contact area between the second phosphor and the photon transmission unit is larger than the contact area between the first phosphor and the photon transmission unit, A radiation monitor characterized by this.

2. In Claim 1, The refractive index of the photon reflection layer is smaller than the refractive index of the first phosphor, A radiation monitor characterized by this.

3. In Claim 1, The photon reflection layer is composed of a bulk metal material, A radiation monitor characterized by this.

4. A radiation detection unit having a phosphor that emits photons in response to incident radiation, A photon transmission unit that transmits photons emitted from the phosphor of the radiation detection unit, Comprising, The phosphor has a first phosphor and a second phosphor, The first phosphor and the second phosphor are adjacent to each other and arranged in parallel, There is a photon reflection layer between the first phosphor and the second phosphor, The first phosphor, the photon reflection layer, and the second phosphor are in contact with the photon transmission unit, The first phosphor, the second phosphor, and the photon reflection layer have a cylindrical shape, A radiation monitor characterized by this.

5. A radiation detection unit having a phosphor that emits photons in response to incident radiation, A photon transmission unit that transmits photons emitted from the phosphor of the radiation detection unit, Comprising, The phosphor has a first phosphor and a second phosphor, The first phosphor and the second phosphor are adjacent to each other and arranged in parallel, There is a photon reflection layer between the first phosphor and the second phosphor, The first phosphor, the photon reflection layer, and the second phosphor are in contact with the photon transmission unit, The first phosphor, the second phosphor, and the photon reflection layer have a spherical shape, A radiation monitor characterized by this.

6. In Claim 1, 4 or 5, The photon transmission unit is configured to include a plurality of photon transmission units at a connection portion with the radiation detection unit. A radiation monitor characterized by the above. **Claim 7** A radiation detection unit having a phosphor that emits photons in response to incident radiation, A photon transmission unit that transmits photons emitted from the phosphor of the radiation detection unit, Comprising: The phosphor has a first phosphor and a second phosphor, The first phosphor and the second phosphor are adjacent to each other and arranged in parallel, There is a photon reflection layer between the first phosphor and the second phosphor, The first phosphor, the photon reflection layer, and the second phosphor are in contact with the photon transmission unit, The radiation detection unit has a third phosphor and a second photon reflection layer, The second photon reflection layer is disposed between the third phosphor and the first phosphor. A radiation monitor characterized by the above. **Claim 8** A radiation detection unit having a phosphor that emits photons in response to incident radiation, A photon transmission unit that transmits photons emitted from the phosphor of the radiation detection unit, Comprising: The phosphor has a first phosphor and a second phosphor, The first phosphor and the second phosphor are adjacent to each other and arranged in parallel, There is a photon reflection layer between the first phosphor and the second phosphor, The first phosphor, the photon reflection layer, and the second phosphor are in contact with the photon transmission unit, There is a photon absorption layer between the first phosphor and the photon transmission unit. A radiation monitor characterized by the above. **Claim 9** A radiation detection unit having a phosphor that emits photons in response to incident radiation, A photon transmission unit that transmits photons emitted from the phosphor of the radiation detection unit, Comprising: The phosphor has a first phosphor and a second phosphor, The first phosphor and the second phosphor are adjacent to each other and arranged in parallel, There is a photon reflection layer between the first phosphor and the second phosphor, The first phosphor, the photon reflection layer, and the second phosphor are in contact with the photon transmission unit, The first phosphor and the second phosphor are composed of different compositions. A radiation monitor characterized by the above. **Claim 10** A radiation detection unit having a phosphor that emits photons in response to incident radiation, A photon transmission unit that transmits photons emitted from the phosphor of the radiation detection unit, Comprising: The phosphor has a first phosphor and a second phosphor, The first phosphor and the second phosphor are adjacent to each other and arranged in parallel, It has a photon reflection layer between the first phosphor and the second phosphor, The first phosphor, the photon reflection layer, and the second phosphor are in contact with the photon transmission part, A photodetector that converts photons transmitted from the photon transmission part into an electrical pulse signal, A counter that counts the electrical pulse signal input from the photodetector, An analysis and display device that converts the count rate of the electrical pulse signal counted by the counter into a radiation dose rate and displays it, Comprising, A radiation monitor characterized by this.

11. A radiation detection unit having a phosphor that emits photons in response to incident radiation, A photon transmission part that transmits photons emitted from the phosphor of the radiation detection unit, Comprising, The phosphor has a first phosphor and a second phosphor, The first phosphor and the second phosphor are adjacent to each other and arranged in parallel, It has a photon reflection layer between the first phosphor and the second phosphor, A method for detecting radiation using a radiation monitor, characterized in that the first phosphor, the photon reflection layer, and the second phosphor are in contact with the photon transmission part, By adjusting the ratio between the contact area of the second phosphor and the photon transmission part and the contact area of the first phosphor and the photon transmission part, the sensitivity to low-energy radiation and high-energy radiation is adjusted, A method for detecting radiation, characterized by this.

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