JP2022119660A - Scintillator material and radiation detection device - Google Patents

Abstract

To provide a scintillator material which has excellent moisture resistance and emits visible light excellently upon receiving a radiation, and a radiation detection device.SOLUTION: A scintillator material which is excited by a radiation and emits visible light contains a phosphor material represented by general formula (M1-aSra)7(SiO3)6X2:Eu2+b.SELECTED DRAWING: Figure 1

Description

The present invention relates to a scintillator material and a radiation detection device.

Iodides such as NaI:Tl and CaI:Tl have been conventionally used in radiation detectors as scintillator materials that emit visible light when excited by radiation. The iodide-based scintillator material has deliquescent properties such that it takes in moisture in the air and turns into an aqueous solution, and must be sealed in a highly airtight container before use. Therefore, in a conventional radiation detection device, an iodide-based scintillator material and a light detection unit are sealed in a container, which is an aluminum can, and a glass window member is adhered to the light extraction port, and light is placed in the container. Visible light was detected by the detector.

JP 2019-074358 A

However, since a small amount of water vapor in the outside air enters the container through the bonding portion between the container and the window member, the iodide-based scintillator deteriorates due to hydrolysis. had to be done properly. In addition, in order to suppress the intrusion of moisture into the container, it is necessary to seal the container with a high degree of airtightness.

SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to provide a scintillator material and a radiation detecting device which are excellent in moisture resistance and can emit visible light under radiation.

In order to solve the above problems, the scintillator material of the present invention is a scintillator material that emits visible light when excited by radiation, and has the general formula (M _{1-a Sra} ) ₇ (SiO ₃ ) ₆ X ₂ : characterized by containing a phosphor material represented by Eu ²⁺ _b (here, M is a divalent metal element, X is a halogen element, and satisfies 0≦a≦1 and 0≦b≦1) and

Such a scintillator material of the present invention is excellent in moisture resistance by using the phosphor material (Culms phosphor) represented by the above general formula, and can satisfactorily emit visible light by radiation.

In one aspect of the present invention, M in the general formula is composed of a divalent metal element containing Ca or Ba.

In one aspect of the present invention, X in the general formula includes at least Cl or one halogen element having an atomic weight larger than Cl.

In one aspect of the present invention, X in the general formula contains Br and is represented by (M _1-a Sr _a ) ₇ (SiO ₃ ) ₆ X _2-c Br _c :Eu ²⁺ _b .

In one aspect of the present invention, the composition ratio of Br is in the range of 0.2≦c≦2.0.

In one aspect of the present invention, the phosphor material is a single crystal or a polycrystal.

In one aspect of the present invention, the powder of the phosphor material is contained in a binder.

A radiation detection apparatus according to the present invention includes any one of the scintillator materials described above and a photodetector that detects a wavelength of 530 nm or more and 560 nm or less.

INDUSTRIAL APPLICABILITY The present invention can provide a scintillator material and a radiation detection device which are excellent in moisture resistance and can emit visible light favorably when exposed to radiation.

1 is a schematic diagram showing the structure of a radiation detection device 10 using a scintillator material according to a first embodiment; FIG. FIG. 3 is a schematic diagram showing the structure of a radiation detection device 20 using a scintillator material according to a second embodiment; FIG. 2 is a schematic diagram showing a measuring device 30 for gamma ray absorption of scintillator material.

(First embodiment)
BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. The same or equivalent constituent elements, members, and processes shown in each drawing are denoted by the same reference numerals, and duplication of description will be omitted as appropriate. FIG. 1 is a schematic diagram showing the structure of a radiation detection device 10 using a scintillator material according to this embodiment. As shown in FIG. 1 , the radiation detection apparatus 10 includes a container 11 , a window member 12 , a scintillator material 13 , a photomultiplier tube 14 (PMT: PhotoMultiplier Tube), and a bleeder circuit 15 .

The container 11 is a substantially cylindrical member having an opening, and accommodates a scintillator material 13 , a photomultiplier tube 14 and a bleeder circuit 15 inside. A window member 12 is airtightly fixed to the opening with an adhesive or the like. Although the material constituting the container 11 is not limited, aluminum can be used as an example. Further, the shape of the container 11 is not limited to a cylindrical shape, and can be appropriately designed according to the shape and size of each member accommodated therein. A wiring hole (not shown) is formed in the container 11, and wiring is connected to the bleeder circuit 15 from the outside through the wiring hole.

The window member 12 is a plate-like member made of a radiation-transmitting material, and is arranged at the opening of the container 11 to hermetically seal the inside of the container 11 . A material for forming the window member 12 is not limited, and a known glass material can be used. Adhesive or the like is applied between the outer periphery of the window member 12 and the opening of the container 11, and is airtightly sealed to prevent water vapor from entering through the gap.

The scintillator material 13 is arranged between the window member 12 and the photomultiplier tube 14 and is a member containing a fluorescent material that emits visible light when irradiated with radiation. In this embodiment, the fluorescent material is represented by the general formula (M _1-a Sr _a ) ₇ (SiO ₃ ) ₆ X ₂ :Eu ²⁺ _b (where M is a divalent metal element, X is a halogen element, and 0 A phosphor material (hereinafter also referred to as a Krums phosphor) represented by the range satisfying ≦a≦1 and 0≦b≦1 is used. This phosphor material is excited by being irradiated with radiation, and emits light in a wavelength range of 530 nm or more and 560 nm or less. The scintillator material 13 has a structure in which a single crystal or polycrystal of a phosphor material is processed into powder and dispersed in a silicone resin. Although the ratio of the phosphor material contained in the scintillator material 13 is not limited, it is preferably in the range of 5 to 50% by weight, for example. If the amount of the phosphor material is less than 5% by weight, radiation cannot be sufficiently absorbed and light emitted. I don't like it. Moreover, it is preferable that the particle size of the phosphor material contained in the scintillator material 13 is in the range of 70 μm or less in the median particle size. When the median particle size of the phosphor material is larger than 70 μm, it becomes difficult to disperse the phosphor material well in the silicone resin.

The photomultiplier tube 14 is a member that detects a minute amount of photons and outputs an electrical signal. A known structure can be used for the photomultiplier tube 14. As an example, a photocathode, a plurality of secondary electron multiplying electrodes (dynodes), an anode, and other electrodes are placed in a high-vacuum glass container. Those having an enclosed structure can be used. A scintillator material 13 is arranged on the entrance window side of the photomultiplier tube 14, and a bleeder circuit 15 is connected to the output side.

The bleeder circuit 15 is a member that supplies voltage from the high-voltage power supply to the photomultiplier tube 14 through a plurality of dividing resistors and outputs current from the photomultiplier tube 14 . A plurality of voltages from a high voltage power supply are supplied to each dynode of photomultiplier tube 14 . The output of the bleeder circuit 15 is transmitted as a detection signal to an external signal processing section via wiring (not shown).

In the radiation detection apparatus 10 shown in FIG. 1, when radiation such as gamma rays is incident on the scintillator material 13 through the window member 12, the phosphor material in the scintillator material 13 is excited, and yellow light with a wavelength range of 530 nm to 560 nm is emitted. Glow with light. Photons of yellow light emitted by the scintillator material 13 reach the photocathode through the incident window of the photomultiplier tube 14 and are converted into electrons by the photocathode. When the electrons generated by the photocathode collide with the dynode, a large number of electrons are emitted by the voltage applied to the dynode. is amplified like an avalanche. A current generated by electrons amplified by the photomultiplier tube 14 is transmitted as a detection signal to an external signal processing unit via a bleeder circuit, and the signal processing unit calculates the number of photons from the relationship between the photons, the current, and the detection signal. Further, the signal processing unit calculates the intensity of radiation from the calculated number of photons.

Next, the phosphor material (Culms phosphor) used for the scintillator material 13 of this embodiment will be described in more detail. In the general formula (M _1-a Sr _a ) ₇ (SiO ₃ ) ₆ X ₂ :Eu ²⁺ _b of the phosphor material described above, the composition M may be composed of a divalent metal element containing Ca or Ba. preferable. By including a divalent metal element having an atomic weight equal to or greater than Ca in the composition M, the specific gravity of the phosphor material contained in the scintillator material 13 is increased to absorb more radiation and increase the amount of visible light emitted. can do.

Moreover, the composition X in the above general formula preferably contains at least Cl or one halogen element having an atomic weight larger than Cl. By including a halogen element having an atomic weight equal to or greater than Cl in the composition X, the specific gravity of the phosphor material contained in the scintillator material 13 is increased to absorb more radiation and increase the amount of visible light emitted. can.

Further, it is preferable that the halogen element of the composition X includes Br, and the general formula is (M _{1-a Sra} ) ₇ (SiO ₃ ) ₆ X _2-c Br _c :Eu ²⁺ _b . Also, the composition ratio of Br is preferably in the range of 0.2≦c≦2.0. By including Br in the halogen element, the absorption of radiation such as gamma rays can be increased, and the amount of visible light emission can be increased.

As described above, in the radiation detection apparatus 10 of the present embodiment, the scintillator material 13 uses a phosphor material represented by the general formula (M _1-a Sr _a ) ₇ (SiO ₃ ) ₆ X ₂ :Eu ²⁺ _b As a result, visible light emitted by radiation can be detected with excellent moisture resistance, and radiation detection sensitivity can be enhanced.

(Second embodiment)
Next, a second embodiment of the invention will be described with reference to FIG. The description of the content that overlaps with the first embodiment is omitted. FIG. 2 is a schematic diagram showing the structure of a radiation detection device 20 using a scintillator material according to this embodiment. As shown in FIG. 1 , the radiation detection device 20 includes a light receiving element 21 and a scintillator material 23 .

The light receiving element 21 is a member that is made of a semiconductor material and generates electrons by receiving light. The light-receiving element 21 can use a known element and its material and structure are not limited. For example, a photodiode (PD) or an avalanche photodiode (APD: Avalanche Photo Diode) can be used. A wire is connected to an electrode (not shown) of the light receiving element 21, and a voltage or current corresponding to the intensity of light is output through the wire.

The scintillator material 23 is arranged on the light receiving surface side of the light receiving element 21 and is a member containing a fluorescent material that emits visible light when irradiated with radiation. As in the first embodiment, this embodiment also uses a phosphor material represented by the general formula (M _{1-a Sra} ) ₇ (SiO ₃ ) ₆ X ₂ :Eu ²⁺ _b as the phosphor material.

In the radiation detection apparatus 20 shown in FIG. 2, when radiation such as gamma rays is incident on the scintillator material 23, the phosphor material in the scintillator material 23 is excited and emits yellow light with a wavelength range of 530 nm to 560 nm. Photons of yellow light emitted by the scintillator material 23 reach the light receiving surface of the light receiving element 21, and a current or voltage depending on the intensity of the light is transmitted to an external signal processing unit as a detection signal. The signal processing unit calculates the number of photons and the intensity of radiation from the detection signal.

In the radiation detection apparatus 20 of the present embodiment as well, the scintillator material 13 is made of a phosphor material represented by the general formula (M _1-a Sr _a ) ₇ (SiO ₃ ) ₆ X ₂ :Eu ²⁺ _b . It can detect visible light emitted by radiation, and can increase radiation detection sensitivity.
(Measurement of luminescence amount by gamma ray irradiation)
As the scintillator material 13 of the radiation detection device shown in FIG. 1, materials of Comparative Example 1 and Examples 1 to 6 shown below were used, and the amount of light emitted by gamma rays was measured. In this embodiment, 662 keV of ¹³⁷ Cs is used as the gamma ray source. In Examples 1 to 6, the obtained phosphor material was processed into a powder having a median particle size of about 12 μm, and 30% by weight of the phosphor material was dispersed in a silicone resin to form a disc having a diameter of 50 mm and a thickness of 3 mm. A scintillator material 13 was obtained by shaping the material into a shape.

(Comparative example 1)
A commercially available BGO (Bi ₄ Ge ₃ O ₁₂ ) was used as the scintillator material 13 . When luminescence due to gamma ray irradiation was measured with the radiation detection apparatus of FIG. 1, a luminescence amount of 15,000 [photons/Mev] was obtained.

(Example 1)
A phosphor material represented by ( _Ca0.4 , _{Sr0.58 , Eu0.02} ) _{7 (} SiO3) _6Cl2 .
SiO ₂ , Eu ₂ O ₃ , Ca(OH) ₂ and SrCl ₂ .6H ₂ O were prepared as raw materials, and the molar ratio of these was 6.0:0.07:2.8:4.06. Each raw material was weighed and placed in an alumina mortar, and pulverized and mixed for about 30 minutes to obtain a raw material mixture. This raw material mixture was placed in an alumina crucible and fired in an electric furnace in a reducing atmosphere in an atmosphere (H ₂ /N ₂ ) of (5/95) at 1030° C. for 5 to 40 hours to obtain a fired product. The obtained fired product was carefully washed with warm pure water to obtain a phosphor material of Example 1. When luminescence due to gamma ray irradiation was measured with the radiation detection apparatus of FIG. 1, a luminescence amount of 25,000 [photons/Mev] was obtained.

(Example 2)
A phosphor material represented by ( _Ca0.4 , _Sr0.45 , _Ba0.05 , _Eu0.1 ) ₇ ( _SiO3 ) ₆ ( _Cl0.9 , _I0.1 ) ₂ .
SiO ₂ , Eu ₂ O ₃ , Ca(OH) ₂ , SrCl ₂ .6H ₂ O, BaCO ₃ and CaI ₂ were prepared as raw materials, and their molar ratios were 6.0:0.35:2.6: The raw materials were weighed so that 3.15:0.35:0.2, and the weighed raw materials were placed in an alumina mortar and pulverized and mixed for about 30 minutes to obtain a raw material mixture. This raw material mixture was placed in an alumina crucible and fired in an electric furnace in a reducing atmosphere in an atmosphere (H ₂ /N ₂ ) of (5/95) at 1030° C. for 5 to 40 hours to obtain a fired product. The obtained fired product was carefully washed with warm pure water to obtain a phosphor material of Example 2. When luminescence due to gamma ray irradiation was measured with the radiation detection apparatus of FIG. 1, a luminescence amount of 24,500 [photons/Mev] was obtained.

(Example 3)
Phosphor represented by _{( Ca0.4} , _Sr0.45 , _Ba0.05 , _Eu0.1 ) ₇ (SiO3) ₆ ( _Cl0.8 , _Br0.1 , _I0.1 ) ₂ material.
SiO ₂ , Eu ₂ O ₃ , Ca(OH) ₂ , SrCl ₂ .6H ₂ O, BaCO ₃ , SrBr ₂ and CaI ₂ were prepared as raw materials, and their molar ratio was 6.0:0.35:2. .6: 3.05: 0.35: 0.1: 0.2, each weighed raw material was placed in an alumina mortar and pulverized and mixed for about 30 minutes to obtain a raw material mixture. This raw material mixture was placed in an alumina crucible and fired in an electric furnace in a reducing atmosphere in an atmosphere (H ₂ /N ₂ ) of (5/95) at 1030° C. for 5 to 40 hours to obtain a fired product. The obtained fired product was carefully washed with warm pure water to obtain a phosphor material of Example 3. When luminescence due to gamma ray irradiation was measured with the radiation detection apparatus of FIG. 1, a luminescence amount of 24,200 [photons/Mev] was obtained.

(Example 4)
A phosphor _material represented by ( _Ca0.35 , _Sr0.45 , _Ba0.05 , _Eu0.15 ) ₇ ( _SiO3 ) _6Cl1.6 , _Br0.2 , _I0.2 .
SiO ₂ , Eu ₂ O ₃ , Ca(OH) ₂ , SrCO ₃ , BaCO ₃ , SrCl ₂ .6H ₂ O, SrBr ₂ and CaI ₂ were prepared as raw materials, and their molar ratio was 6.0:0. 525: 2.35: 2.25: 0.35: 0.8: 0.1: 0.1, put each weighed raw material in an alumina mortar, pulverize and mix for about 30 minutes, and obtain a raw material mixture got This raw material mixture was placed in an alumina crucible and fired in an electric furnace in a reducing atmosphere in an atmosphere (H ₂ /N ₂ ) of (5/95) at 1030° C. for 5 to 40 hours to obtain a fired product. The obtained fired product was carefully washed with warm pure water to obtain a phosphor material of Example 4. When luminescence due to gamma ray irradiation was measured with the radiation detection apparatus of FIG. 1, a luminescence amount of 26,100 [photons/Mev] was obtained.

(Example 5)
A phosphor _material represented by ( _Ca0.4 , _Sr0.58 , _Eu0.02 ) ₇ ( _SiO3 ) _6Cl0.5 , _Br1.5 .
SiO ₂ , Eu ₂ O ₃ , Ca(OH) ₂ , SrCO ₃ , BaCO ₃ , SrCl 2.6H ₂ O, and SrBr _{2 were} prepared as raw materials, and their molar ratio was 6.0:0.07:2. .8:3.06:0.25:0.75, and the weighed raw materials were placed in an alumina mortar and pulverized and mixed for about 30 minutes to obtain a raw material mixture. This raw material mixture was placed in an alumina crucible and fired in an electric furnace in a reducing atmosphere in an atmosphere (H ₂ /N ₂ ) of (5/95) at 1030° C. for 5 to 40 hours to obtain a fired product. The obtained fired product was carefully washed with warm pure water to obtain a phosphor material of Example 5. When luminescence due to gamma ray irradiation was measured with the radiation detection apparatus of FIG. 1, a luminescence amount of 28,500 [photons/Mev] was obtained.

(Example 6)
_A phosphor material represented by ( _Ca0.4 , _Sr0.45 , _Ba0.05 , _Eu0.1 ) ₇ ( _SiO3 ) _6Cl0.1 , _Br1.9 .
SiO ₂ , Eu ₂ O ₃ , Ca(OH) ₂ , SrCO ₃ , BaCO ₃ , SrCl 2.6H ₂ O and CaBr _{2 were} prepared as raw materials, and the molar ratio of these was 6.0:0.35:1. .85:3.1:0.35:0.05:0.05, and the weighed raw materials were placed in an alumina mortar and pulverized and mixed for about 30 minutes to obtain a raw material mixture. This raw material mixture was placed in an alumina crucible and fired in an electric furnace in a reducing atmosphere in an atmosphere (H ₂ /N ₂ ) of (5/95) at 1030° C. for 5 to 40 hours to obtain a fired product. The obtained fired product was carefully washed with warm pure water to obtain a phosphor material of Example 6. When luminescence due to gamma ray irradiation was measured with the radiation detection apparatus of FIG. 1, a luminescence amount of 27,300 [photons/Mev] was obtained.

Table 1 shows the measurement results of the amount of light emitted by gamma ray irradiation in Comparative Example 1 and Examples 1 to 6. As shown in Table 1, the general formula (M _1-a Sr _a ) ₇ (SiO ₃ ) ₆ X ₂ :Eu ²⁺ _b (here, M is a divalent metal element, X is a halogen element, 0 ≤ a ≤ 1 and 0 ≤ b ≤ 1). Further, by using the phosphor material (Culms phosphor) represented by the above general formula, it is possible to obtain a larger amount of light emission than BGO, which has been conventionally used, and to improve radiation detection sensitivity.

Composition M in the general formula contains a divalent metal element containing Ca or Ba, and composition X contains at least Cl or one halogen element having an atomic weight larger than Cl. In particular, when the composition X contains Br, the phosphor material can be represented by the general formula (M _{1-a Sra} ) ₇ (SiO ₃ ) ₆ X _2-c Br _c :Eu ²⁺ _b . At this time, when the composition ratio of Br is in the range of 0.2≦c≦2.0, the detected amount of photons is large, and the radiation detection sensitivity is improved.

(Measurement of gamma ray absorption in scintillator material)
Next, the gamma ray absorbance of the scintillator materials produced in Examples 1 and 4 to 6 was measured. FIG. 3 is a schematic diagram showing an apparatus 30 for measuring the gamma ray absorptance of scintillator materials. As shown in FIG. 3 , the gamma ray absorptance measuring device 30 includes a photomultiplier tube 31 , a detection scintillator 32 , an evaluation sample 33 , a light shielding sheet 34 and a radiation source 35 .

The photomultiplier tube 31 is a member that detects a minute amount of photons and outputs an electrical signal. The scintillator 32 for detection is arranged at the entrance window of the photomultiplier tube 31, is a member containing BGO, and is excited by the radiation emitted from the radiation source 35 to emit visible light. The evaluation sample 33 is a scintillator material containing the phosphor material produced in Examples 1 and 4 to 6 described above, and is arranged between the photomultiplier tube 31 and the scintillator 32 for detection. The light shielding sheet 34 is a sheet-like member made of a material that blocks visible light and transmits radiation, and is arranged to cover the entrance window of the photomultiplier tube 31 and the detection scintillator 32 . Also, the light shielding sheet 34 is sandwiched between the scintillator 32 for detection and the evaluation sample 33 . The radiation source 35 is a device for irradiating radiation, and uses 60 keV of ²⁴¹ Am in this embodiment.

In the measurement apparatus 30 shown in FIG. 3, gamma rays emitted from the radiation source 35 pass through the evaluation sample 33 and the light shielding sheet 34 and reach the scintillator 32 for detection. In the detection scintillator 32, BGO is excited by gamma rays to emit visible light. Photons emitted by the detection scintillator 32 reach the photomultiplier tube 14 and are output to the signal processing section as a detection signal. The signal processor calculates the number of photons based on the detection signal.

At this time, the phosphor material is also excited by the gamma rays incident on the evaluation sample 33 and emits visible light. Only the light emitted at 32 is obtained. Therefore, by comparing the number of photons detected by the photomultiplier tube 31, the amount of gamma rays absorbed by the evaluation sample 33 can be measured.

(Comparative example 2)
Comparative Example 2 is obtained by measuring the light emission amount of the detection scintillator 32 with the photomultiplier tube 31 in the measuring apparatus 30 shown in FIG. In the measuring device 30, the light emission amount of the detection scintillator 32 was measured by the photomultiplier tube 31 with Examples 1 and 4 to 6 placed as the evaluation sample 33, and compared with Comparative Example 2, the gamma ray absorptance was measured. Calculated. Here, the gamma ray absorption rate _{R A} is the ratio _R (N _B /N _A ) is obtained and calculated as R _A = (100-R)%.

As shown in Table 2, in Examples 1 and 4 to 6, the scintillator material of evaluation sample 33 containing a phosphor material (Krums phosphor) absorbed 30% or more of gamma rays, and the phosphor material ( It can be seen that the Krums phosphor) can be excited with high efficiency to emit visible light.

The present invention is not limited to the above-described embodiments, but can be modified in various ways within the scope of the claims, and can be obtained by appropriately combining technical means disclosed in different embodiments. is also included in the technical scope of the present invention.

Reference Signs List 10, 20 Radiation detection device 30 Measurement device 11 Container 12 Window member 13, 23 Scintillator material 14, 31 Photomultiplier tube 15 Bleeder circuit 21 Light receiving element 32 Scintillator for detection 33 Evaluation sample 34 ... Shielding sheet 35 ... Radiation source

Claims (8)

A scintillator material that emits visible light when excited by radiation,
General formula (M _1-a Sr _a ) ₇ (SiO ₃ ) ₆ X ₂ : Eu ²⁺ _b
(Here, M is a divalent metal element, X is a halogen element, and the range satisfies 0 ≤ a ≤ 1 and 0 ≤ b ≤ 1)
A scintillator material containing a phosphor material represented by: The scintillator material according to claim 1,
A scintillator material, wherein M in the general formula is composed of a divalent metal element containing Ca or Ba. The scintillator material according to claim 1 or 2,
A scintillator material, wherein X in the general formula contains at least Cl or one halogen element having an atomic weight larger than Cl. The scintillator material according to claim 3,
X in the general formula contains Br,
(M _1-a Sr _a ) ₇ (SiO ₃ ) ₆ X _2-c Br _c : A scintillator material characterized by being represented by Eu ²⁺ _b . The scintillator material according to claim 4,
The scintillator material, wherein the composition ratio of Br is in the range of 0.2≦c≦2.0. The scintillator material according to any one of claims 1 to 5,
A scintillator material comprising the phosphor material in the form of a single crystal or a polycrystal. The scintillator material according to any one of claims 1 to 6,
A scintillator material comprising a powder of the phosphor material contained in a binder. a scintillator material according to any one of claims 1 to 7;
1. A radiation detection apparatus comprising a photodetector that detects a wavelength of 530 nm or more and 560 nm or less.

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