JP2007024629A - IMAGING PLATE FOR gamma-RAY SENSITIVITY DESENSITIZED NEUTRON AND PARTICLE BEAM - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a neutron imaging plate with a low γ-ray sensitivity. <P>SOLUTION: A powder obtained by uniformly mixing a fluorescent powder of BaFBr:Eu<SP>2+</SP>and a boric acid (H<SB>3</SB><SP>10</SP>BO<SB>3</SB>) powder with a<SP>10</SP>B isotope composition ratio of 90% is applied on a metal substrate and sintered. Defects are thermally diffused and introduced to the surface of the fluorescent powder of BaFBr:Eu<SP>2+</SP>to obtain a surface sensitive stimulable phosphor. The inhibiting capacity of an α particle and an<SP>7</SP>Li particle emitted when<SP>10</SP>B capatures a neutron is greater than the inhibiting capacity of an electron emitted by the γ beam functioning as a back ground is used to lower the sensitivity to the γ beam. Thus, the imaging plate with desensitized γ-beam sensitivity is obtained. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The low-gamma-sensitivity neutron imaging plate of the present invention is a high-sensitivity, high-spatial-resolution neutron image detector for high-sensitivity, high-spatial-resolution neutron image detectors for neutron scattering experiments using neutrons generated from nuclear reactors. Used as an image detector. It can also be used for neutron dose measurement or neutron distribution monitoring in the reactor facility. Furthermore, it is used as a profile monitor for a neutron beam generated in a nuclear reactor or a pulsed neutron beam generated using a high-intensity proton accelerator.

  On the other hand, the low-gamma-ray-sensitized particle beam imaging plate is used as a beam profile monitor such as a proton beam or a heavy particle beam. It is also used as an α-ray dose monitor or an α-ray image detector.

As a neutron imaging plate, Gd ₂ O ₃ containing Gd having a large neutron capture cross section is used as a neutron converter, and a neutron imaging plate using BaFBr: Eu ²⁺ as a stimulable phosphor is BAS-ND from Fuji Photo Film. (Non-Patent Document 1). As shown in the conventional example of FIG. 9, this imaging plate has been manufactured by mixing a stimulable phosphor BaFBr: Eu ²⁺ powder and a neutron converter Gd ₂ O ₃ powder with an adhesive and applying the mixture to a substrate. However, since this commercially available neutron imaging plate uses Gd ₂ O ₃ as a neutron converter, although the neutron capture cross section is large, secondary electrons emitted by the (n, e) reaction are as small as about 80 keV and Gd Its own atomic number Z is as large as 64. For this reason, there is a drawback that the gamma-ray sensitivity characteristic (influence on the γ-ray bag round), which is a very large performance index in detecting a neutron image, is poor.

For this reason, it is necessary to use a light element as a neutron converter and an element that emits large energy by a neutron capture reaction. There is ¹⁰ B (boron) as an element meeting this condition. However, various stimulable phosphors such as SrBPO ₅ : Eu ²⁺ having ¹⁰ B as a constituent element have been developed (Non-patent Document 2), but the composition ratio of ¹⁰ B in the stimulable phosphor is low. In addition, the photostimulable luminescence properties are not commercially available because they are not as good as BaFX: Eu ²⁺ .

On the other hand, as shown in FIG. 10, in order to reduce gamma rays, boric anhydride (B ₂ O ₃ ) is melted and vitrified at a low temperature to be used as a neutron converter and at the same time as an adhesive. A vitrified imaging plate has been developed (Patent Document 1). However, although the gamma ray sensitivity is somewhat lower than before, it is not a sufficient value.

In addition, little development has been done on particle beam imaging plates aimed at reducing the sensitivity of gamma rays.
N. Niimura et al .: An imaging plate neutron detector, Nucl. Instrum & Methods A349, 521 (1994) and Nuclear Industry, 41 [6], 54 (1995) K. Sakasai et al., A SrBPO5: Eu2 + storage phosphor for neutron imaging, Apl.phys.A74, [Suppl.], S1589-S1591 (2002) Japanese Patent Application No. 2005-53919

As described in the background art above, the commercially available imaging plates have a drawback that the gamma ray sensitivity characteristic, which is a very large performance index for detecting a neutron image, is poor, and in order to solve this Stimulable phosphors such as SrBPO ₅ : Eu ²⁺ having ¹⁰ B as a constituent element have been developed, but are not yet commercially available, and furthermore, low temperature melting of boric anhydride (B ₂ O ₃ ) A vitrified imaging plate has been developed that uses it as a neutron converter and at the same time as an adhesive, but still has problems such as not being sufficient. Therefore, the present invention has been invented as a result of research in order to solve these problems.

In the present invention, the phosphor powder is uniformly mixed with boric acid (H ₃ ¹⁰ BO ₃ ) powder containing ¹⁰ B, which is a neutron converter, and then sintered for a certain time within an appropriate temperature range. It was confirmed that defects were generated by thermal diffusion on the surface of the film and that the surface portion became a stimulable phosphor.

That is, in the present invention, BaFX: Eu ²⁺ (X: Br, Cl or a mixture of Br and Cl) phosphor powder and boric acid (H ₃ ¹⁰ BO ₃ ) having a composition ratio of ¹⁰ B isotope of 80% or more. Powder uniformly mixed with powder is applied to a metal substrate and sintered for a certain time within a temperature range of 500 ° C. to 700 ° C., BaFX: Eu ²⁺ (X: Br, Cl or a mixture of Br and Cl) This is a low gamma-ray-sensitized neutron imaging plate in which defects are introduced into the surface of the phosphor powder by thermal diffusion to form a surface-sensitive photostimulable phosphor.

In the present invention, when this surface-sensitive photostimulable phosphor is used, the blocking ability of α particles and ⁷ Li particles emitted when ¹⁰ B, which is a neutron converter, captures neutrons is generated by the background gamma rays. Since it is much larger than the stopping power of electrons, it is possible to greatly reduce the sensitivity to gamma rays. Further, since ¹⁰ B which is a neutron converter enters the sensitive phosphor portion on the surface, the stimulable phosphor portion can absorb the energy of α particles and ⁷ Li particles without loss. A gamma-ray sensitive neutron imaging plate can be realized.

(Example 1)
As Example 1, after applying a uniformly mixed powder of BaFBr: Eu ²⁺ phosphor powder and boric acid (H ₃ ¹⁰ BO ₃ ) powder having a ¹⁰ B isotope composition ratio of 90% to a metal substrate A low-gamma-ray-sensitized neutron imaging plate will be described in which defects are introduced into the surface of the BaFBr: Eu ²⁺ phosphor powder by thermal diffusion to form a surface-sensitive photostimulable phosphor.

As shown in the fabrication method of FIG. 1, in this embodiment, the photostimulable phosphor, which is a detection material of the neutron imaging plate, is subjected to a thermal diffusion treatment based on BaFBr: Eu ²⁺ that hardly exhibits stimulable fluorescence. It is characterized by being formed on the surface of BaFBr: Eu ²⁺ . FIG. 2 shows a comparison between the structure of a conventional photostimulable phosphor and the structure of the surface-sensitive photostimulable phosphor of the present invention. When a surface-sensitive photostimulable phosphor is used, the stopping power of α particles and ⁷ Li particles emitted when ¹⁰ B, which is a neutron converter, captures neutrons is the stopping power of electrons generated by gamma rays as a background. Since it becomes larger, the sensitivity to gamma rays can be greatly reduced. Moreover, since ¹⁰ B, which is a neutron converter, partially enters the sensitive phosphor portion on the surface, the energy of α particles and ⁷ Li particles (approximately 2.3 MeV in total) is reduced with little loss. It is possible to absorb the stimulable phosphor portion, and to realize low gamma ray sensitivity of the neutron imaging plate. Boric acid (H ₃ ¹⁰ BO ₃ ) powder is sintered to ¹⁰ B ₂ O _{3 .}

The imaging will be described. The particle beam (α ray and ⁷ Li particle) emitted from ¹⁰ B isotope which has a role as a neutron converter is applied to the surface portion of the surface sensitive photostimulable phosphor BaFBr: Eu ^2+. Accumulate as a latent image. The accumulated latent image is scanned with excitation laser light after neutron irradiation to obtain an accumulation amount of particle beams caused by neutrons in the imaging plate, and finally a neutron image is detected. Since the excitation wavelength (635 nm) and the stimulable fluorescence wavelength (400 nm) are the same as those of the commercially available BAS series or BAS-ND series, it can actually be read by an imaging plate reader BAS-1800 commercially available from Fuji Photo Film. it can.

In this example, Nichia X-ray detection phosphor BaFBr: Eu ²⁺ was used as the phosphor powder. The stimulable fluorescence characteristic of this phosphor was 1/100 or less of the stimulable fluorescence characteristic used in the commercially available BAS-MS imaging plate. ^Further, the composition ratio of ¹⁰ B isotope 90% of boric acid _{^{(H 3}} 10 BO ³⁾ powder was used made by Stella Chemifa for. 750 mg of X-ray detection phosphor BaFBr: Eu ²⁺ powder and 500 mg of boric acid (H ₃ ¹⁰ BO ₃ ) powder were mixed and applied to an aluminum substrate having a size of 5 cm × 5 cm. After coating, sintering was performed at 600 ° C. in an electric furnace. In order to investigate the effect of the heat treatment diffusion, the sintering time was 30 minutes, 1 hour, 1 hour 30 minutes, 2 hours, 3 hours, 4 hours, 8 hours and 10 hours. After sintering, first, the influence of the heat treatment on the fluorescence spectrum was evaluated. As a radiation source for evaluation, α-ray of 5.4 MeV emitted from Am? 241 was used. Since the particles emitted by the neutron capture reaction are α rays and ⁷ Li, almost the same effect as these particle rays can be obtained. The spectrum of prompt fluorescence generated by α-ray irradiation was measured using Hitachi spectrofluorometer F-2500. The result of comparing the case of 30 minutes sintering and the case of 4 hours is shown in FIG. There was almost no change in the shape of the fluorescence spectrum, and the amount of photostimulable fluorescence was about 85%. As a result, it has been found that the characteristics as a phosphor hardly deteriorate even after a long-time thermal diffusion treatment.

  Next, each of the sintered samples was subjected to a sensitivity measurement test for cold neutrons, 60 keV gamma rays, and Co60 gamma rays (about 1200 keV gamma rays) by the method shown in FIG. For reading the image, an imaging plate reader BAS-1800 commercially available from Fuji Photo Film was used. The test results are shown in FIG. The horizontal axis represents the sintering time, and the left vertical axis represents the relative detection efficiency with respect to the BAS-ND neutron imaging plate conventionally used. Since it was confirmed that the sensitivity to cold neutrons increased with increasing sintering time, the surface sensitive layer of the surface sensitive photostimulable phosphor could be obtained by changing the sintering time at a constant sintering temperature. It was confirmed that the thickness of the material changed. In particular, 67% relative neutron detection efficiency was obtained after 10 hours of sintering. On the other hand, the vertical axis on the right side shows the effective gamma ray detection efficiency (corrected by normalization with the neutron detection efficiency) for the BAS-ND neutron imaging plate used conventionally. About 60 keV gamma rays, it has confirmed that it showed a change substantially equivalent to the change of the detection efficiency with respect to a neutron. The firing time up to 3 hours was 2%, and the effective gamma ray sensitivity was 7% even at 10 hours when the maximum neutron detection efficiency was obtained. The reason for showing fluorescence similar to that of neutrons is considered to be due to the apparent increase in electron stopping power when gamma ray energy is low. On the other hand, it was found that the sensitivity to Co60 gamma rays (about 1200 keV gamma rays) was almost constant 1% to 2% without much influence on the sintering time. As a result, it was confirmed that the sensitivity to high energy gamma rays, which is the biggest problem in using the neutron imaging plate, can be reduced by about 50 to 100 times compared to the BAS-ND neutron imaging plate.

Moreover, a low-gamma-ray-sensitized neutron imaging plate was also produced for BaFCl: Eu ²⁺ as a phosphor powder by the same production method as in the above example. As a phosphor powder, X-ray detection phosphor BaFCl: Eu ²⁺ manufactured by Nichia Corporation was used. The stimulable fluorescence characteristic of this phosphor was 1/100 or less of the stimulable fluorescence characteristic used in the commercially available BAS-MS imaging plate. ^Further, the composition ratio of ¹⁰ B isotope 90% of boric acid _{^{(H 3}} 10 BO ³⁾ powder was used made by Stella Chemifa for. BaFCl: Eu ²⁺ as a phosphor with a low gamma-ray-sensitized neutron imaging plate with a sintering time of 1 hour, compared with a low gamma-ray-sensitized neutron imaging plate using a BaFBr: Eu ²⁺ phosphor manufactured with the same neutron detection efficiency As a result, 1.44 and 1.51 were obtained as PSL (value indicating the stimulable fluorescence intensity of Fuji Photo Film BAS1800), respectively. Low-gamma-ray sensitized neutron imaging plate using BaFCl: Eu ²⁺ phosphor The neutron sensitivity was about 5% lower and 95%, almost the same characteristics. In addition, almost the same results were obtained with respect to gamma ray sensitivity.

Further, in the above examples, it was confirmed that the thickness of the surface sensitive layer of the surface sensitive photostimulable phosphor was changed by fixing the firing temperature at 600 ° C. and changing the sintering time. As a constant, the thickness of the surface sensitive layer of the surface sensitive photostimulable phosphor can be controlled by changing the firing temperature.
(Example 2)
As Example 2, a powder obtained by uniformly mixing BaFBr: Eu ²⁺ phosphor powder and boric acid (H ₃ ¹¹ BO ₃ ) powder having a composition ratio of ¹¹ B isotope of 99.9% was applied to a metal substrate. After that, the low-gamma-ray-sensitized particle beam imaging plate which is sintered and introduced into the surface of the BaFBr: Eu ²⁺ phosphor powder by thermal diffusion to form a surface-sensitive photostimulable phosphor will be described. FIG. 6 shows the structure of a low-gamma-sensitized particle beam imaging plate. The structure is the low gamma-ray sensitized neutron imaging plate described in Example 1, and the composition ratio of ¹¹ B isotope is 99 instead of boric acid (H ₃ ¹⁰ BO ₃ ) powder having a composition ratio of ¹⁰ B isotope of 90%. It is the same except that 9% or more boric acid (H ₃ ¹¹ BO ₃ ) powder is used. ^As a boric acid (H ₃ ¹¹ BO ₃ ) powder having a composition ratio of ¹¹ B isotope of 99.9% or more, Toyama Pharmaceutical Co., Ltd. was used. By using this boric acid (H ₃ ¹¹ BO ₃ ), the sensitivity to neutrons can be almost eliminated. As the phosphor powder, the same X-ray detection phosphor BaFBr: Eu ²⁺ manufactured by Nichia Corporation as used in Example 1 was used. The manufacturing method is exactly the same as in the first embodiment. Evaluation of detection sensitivity of Am-241 for 5.4 MeVα ray and 60 keV gamma ray for low-gamma ray sensitive particle beam imaging plate with sintering time of 1 hour using imaging plate reader BAS-1800 marketed by Fuji Photo Film did. As a result of the evaluation, in the case of the conventional BAS-MS imaging plate, the ratio of PSL of gamma rays to α rays (value indicating the stimulable fluorescence intensity of Fuji Photo Film BAS1800) was 0.417, whereas this imaging In play, it was confirmed to be 0.042, an improvement of about 10 times.
Example 3
As Example 3, when using an aluminum plate as a metal substrate in the case where the sintering temperature is used within the range of 620 ° C. or less in Examples 1 and 2, an inorganic glass adhesive is applied to both surfaces of the aluminum plate. A neutron imaging plate with low gamma-ray sensitivity, which is characterized by being used as an image sensor, will be described. When an aluminum plate is used as a metal substrate and a neutron imaging plate with low gamma-ray sensitivity is manufactured in an electric furnace, aluminum gradually evaporates from the surface of the substrate, so that the vapor reacts with the surface of the neutron imaging plate with low gamma-ray sensitivity and partially black. Turn into. For this reason, when using an aluminum plate as a metal substrate, it is necessary to coat with a material having resistance at high temperatures so as not to evaporate from the surface. In the example, BS-600-3, which is Nikko's inorganic adhesive (trade name HEATLESS GLASS) having a heat resistance of 900 ° C., was applied to a 0.3 mm thick aluminum substrate as shown in FIG. Used freshly. As a result of producing a low-gamma-ray sensitive neutron imaging plate using this substrate and performing an evaluation test in the same manner as in Example 1, the coating temperature is effective at a sintering temperature of 620 ° C., and blackening due to aluminum vapor is prevented. It was confirmed that it was possible.
Example 4
As a fourth embodiment, a low-gamma-sensitivity neutron imaging plate characterized by using a titanium (Ti) plate or a titanium alloy plate as a metal substrate in the first and second embodiments will be described. When an aluminum plate is used as a metal substrate and a neutron imaging plate with low gamma-ray sensitivity is manufactured in an electric furnace, aluminum evaporates little by little from the surface of the substrate. Therefore, a titanium (Ti) plate or titanium having a melting point of 1000 ° C. or more. An alloy plate was used. When used as a substrate for a neutron imaging plate, there is a problem of activation by neutrons of the material, but titanium (Ti) is less activated than before, so neutron capture of aluminum, a metal used in neutron irradiation fields, is interrupted. Although it has a cross-sectional area approximately twice as large as the area, it is very small, so there is no practical problem. As a result of a production test of a low-gamma-ray sensitive neutron imaging plate using a titanium (Ti) plate or a titanium alloy plate as a metal substrate, it was confirmed that the surface can be produced in a stable state.
(Example 5)
As Example 5, the emission of photostimulable fluorescence by adding NaCl or NaCO ₃ powder of 0.5% to 2% of the weight of the powder obtained by mixing phosphor powder and boric acid powder in Example 1-4. A low-gamma-sensitivity neutron imaging plate or a low-gamma-sensitivity particle beam imaging plate, which is characterized by increasing the number of particles, will be described.

A low-gamma-ray-sensitized neutron imaging plate was manufactured under the same conditions by adding NaCl powder having a weight of 2% of the mixed powder to the low-gamma-ray-sensitized particle beam imaging plate of Example 1 having a sintering time of 3 hours. A sensitivity measurement test for cold neutrons, 60 keV gamma rays, and Co60 gamma rays (about 1200 keV gamma rays) was performed by the method shown in FIG. As a result, in the case where the 2% by weight NaCl powder of the mixed powder was not added and the neutron sensitivity was evaluated, the PSL values indicating the stimulable fluorescence intensity of Fuji Photo Film BAS1800 were 7.6 and 10. 0 was obtained. As a result, it was confirmed that it could be increased 1.3 times compared to the case where 2% NaCl powder was not added. In addition, the gamma-ray sensitivity characteristics hardly changed.
(Example 6)
In Example 6, instead of the BaFX: Eu ²⁺ (X: Br, Cl or a mixture of Br and Cl) phosphor used as the phosphor in Example 1-5, BaFSrX: Eu ²⁺ (X: Br, Cl or Br) was used instead of the phosphor. This is an example using a phosphor. As an example, the BaFSrBr: Eu ²⁺ phosphor containing strontium (Sr) as a constituent material has almost the same characteristics as the phosphor as BaFBr: Eu ^2+. Gamma-ray-sensitized neutron imaging plates or low-gamma-ray-sensitized particle beam imaging plates can be manufactured.
(Example 7)
In Example 7, when a powder obtained by uniformly mixing phosphor powder and boric acid powder in Example 1-6 is applied to a metal substrate, an inorganic adhesive having a weight of 1% to 5% of the weight of the mixed powder is applied. A low-gamma-sensitized neutron imaging plate or a low-gamma-ray-sensitized particle beam imaging plate, characterized in that the added ethanol or isopropyl alcohol is mixed as a mixing aid in a wet manner and applied to a metal substrate, will be described.

  This will be described with reference to FIG. As a method of applying a uniform mixture of phosphor powder and boric acid powder to a metal substrate, a wet mixing method using a mixture of ethanol or isopropyl alcohol conventionally used is applied to the metal plate. In this case, the boric acid powder creates a band-like pattern due to differentiation. For this reason, if a neutron imaging plate is manufactured by sintering as it is, the uniformity becomes worse and a band-like pattern appears.

In order to prevent this, a mixing aid in which an inorganic adhesive having a weight of 1% to 5% of the weight of the mixed powder is added to ethanol or isopropyl alcohol is prepared and mixed in a wet manner. In the case of Example 1, 750 mg of X-ray detection phosphor BaFBr: Eu ²⁺ powder and 500 mg of boric acid (H ₃ ¹⁰ BO ₃ ) powder are mixed, but in this case 1% by weight of Nikko inorganic adhesive 12.5 mg of BS-600-1 (trade name HEATLESS GLASS) was mixed with ethanol, wet-mixed, and applied to an aluminum substrate having a size of 5 cm × 5 cm. When this sample was baked at 600 ° C for 4 hours, a band-like pattern appeared when it was not added, but when it was added, the neutron imaging plate disappeared and the gamma-ray sensitivity with uniform neutron sensitivity was eliminated. It became a neutron imaging plate.

  The low-gamma-sensitivity neutron imaging plate of the present invention is a high-sensitivity, high-spatial-resolution neutron image detector for high-sensitivity, high-spatial-resolution neutron image detectors for neutron scattering experiments using neutrons generated from nuclear reactors. It can be used as an image detector, and can also be used for neutron dosimetry or neutron distribution monitoring in a nuclear reactor facility. In addition, it can be used to generate a neutron beam generated in a nuclear reactor or a pulsed neutron beam generated using a high-intensity proton accelerator. Used as a profile monitor.

  Furthermore, it is used as a beam profile monitor such as a proton beam or a heavy particle beam, and is also used as an α-ray dose monitor or an α-ray image detector.

After applying uniformly mixed powder of BaFBr: Eu ²⁺ phosphor powder and boric acid (H ₃ ¹⁰ BO ₃ ) powder having a composition ratio of ¹⁰ B isotope of 90% to a metal substrate, sintering is performed. The figure which shows the manufacturing method of the low-gamma-ray sensitivity neutron imaging plate to produce. The figure which compared the structure of the conventional photostimulable phosphor with the structure of the surface sensitive photostimulable phosphor of this invention. The figure which shows the result of having compared the spectrum of the prompt fluorescence in the case of sintering for 30 minutes, and the case of sintering for 4 hours. The figure which shows the method of evaluating the detection characteristic with respect to the neutron and gamma ray of a sintered sample. The figure which shows the sensitivity measurement test result with respect to the cold neutron, 60 keV gamma ray, and Co60 gamma ray of the low gamma ray sensitivity neutron imaging plate whose baking time is 30 minutes to 8 hours. The figure which shows the structure of a low gamma-ray-sensitized particle beam imaging plate. The figure which shows the low gamma-ray-sensitized neutron imaging plate using the board | substrate which apply | coated the 50-micrometer-thick Nikko inorganic adhesive BS-600-3 which has 900 degreeC heat resistance to the aluminum substrate. A low gamma-ray-sensitized neutron imaging plate is manufactured by wet mixing using ethanol with inorganic adhesive weight of 1% to 5% of the mixed powder as a mixing aid, applying it to the substrate and sintering. The figure which shows a method. Stimulable phosphor BaFBr: Eu ²⁺ powder and a neutron converter Gd ₂ O ₃ powder to show the structure of a neutron imaging plates are conventional commercially available fabricated by coating the substrate mixed with glue FIG. Shows the structure of a conventional vitrifying imaging plate to produce by utilizing the fact that the vitrified by melting boric anhydride (B 2 _{O 3).}

Claims (7)

BaFX: Eu ²⁺ (X: Br, Cl or a mixture of Br and Cl) phosphor powder and boric acid (H ₃ ¹⁰ BO ₃ ) powder having a composition ratio of ¹⁰ B isotopes of 80% or more uniformly mixed The applied powder is applied to a metal substrate and sintered within a temperature range of 500 ° C. or higher and 700 ° C. or lower for a certain period of time. BaFX: Eu ²⁺ (X: Br, Cl or a mixture of Br and Cl) Is introduced by thermal diffusion to form a surface-sensitive photostimulable phosphor, and the stopping power of α particles and ⁷ Li particles emitted when ¹⁰ B captures neutrons is the stopping power of electrons generated by background gamma rays. A neutron imaging plate with low gamma-ray sensitivity, which is characterized by lowering the sensitivity to gamma rays by utilizing its larger size. BaFX: Eu ²⁺ (X: Br, Cl or a mixture of Br and Cl) phosphor powder and boric acid (H ₃ ¹¹ BO ₃ ) powder having a composition ratio of ¹¹ B isotopes of 99% or more uniformly mixed The applied powder is applied to a metal substrate and sintered within a temperature range of 500 ° C. or higher and 700 ° C. or lower for a certain period of time. BaFX: Eu ²⁺ (X: Br, Cl or a mixture of Br and Cl) Is made into a surface-sensitive photostimulable phosphor, and the sensitivity to gamma rays is reduced by utilizing the fact that the stopping power of particle beams is larger than the stopping power of electrons generated by the background gamma rays. This is a low-gamma-ray sensitive particle beam imaging plate.   In claim 1 and 2, when using an aluminum plate as a metal substrate when used within a range of 620 ° C. or lower, an inorganic glass adhesive is applied to both sides of the aluminum plate and used. Gamma-ray-sensitized neutron imaging plate and low-gamma-ray-sensitized particle beam imaging plate.   3. The low-gamma-ray-sensitized neutron imaging plate and low-gamma-ray-sensitized particle beam imaging plate according to claim 1, wherein a titanium (Ti) plate or a titanium alloy plate is used as the metal substrate. 5. The emission of stimulable fluorescence is increased by adding 0.5% or more and 2% or less of NaCl or NaCO ₃ powder based on the weight of the mixed powder of phosphor powder and boric acid powder according to any one of claims 1-4. A low-gamma-ray sensitive neutron imaging plate or a low-gamma-sensitized particle beam imaging plate. 6. The low-gamma-ray-sensitized neutron imaging plate or low-gamma-ray-sensitized particle beam imaging plate according to claim 1, wherein a BaFSrX: Eu2 ⁺ phosphor is used instead of the BaFX: Eu2 ⁺ phosphor.   In any one of Claims 1-6, when apply | coating the powder which mixed phosphor powder and boric acid powder uniformly on a metal substrate, the inorganic adhesive of the weight of 0.5 to 5% of the weight of mixed powder is added. A low-gamma-sensitized neutron imaging plate or low-gamma-ray-sensitized particle beam imaging plate, characterized in that the added ethanol or isopropyl alcohol is used as a mixing aid to mix evenly and apply to a metal substrate.