JP7109885B2 - Charged particle radiation measurement method and charged particle radiation measurement device - Google Patents

Description

The present invention relates to a charged particle radiation measuring method and a charged particle radiation measuring device.

In advanced medical care using radiation generators such as heavy ion therapy equipment and basic experiments at related accelerator facilities, it is necessary to accurately and continuously measure the dose and energy of charged particles under conditions of high irradiation density. be. On the other hand, in the case of an accident at a nuclear facility such as a nuclear power plant that uses nuclear fission or in the reactor environment of a nuclear fusion reactor that has been developed in recent years, radiation measurement is required in an environment of high temperature, high environmental load, and high radiation exposure. It is necessary to install equipment and take measurements.

Ion beams generated from accelerator facilities and radiation from nuclear facilities are generally of high density. Measuring instruments must be highly reliable and capable of accurate and long-term measurement even in such environments.

A scintillation detector using a scintillator is used to measure the dose and energy of charged particles. For scintillation detectors, the durability and luminous efficiency of the part containing the luminescent material that converts radiation into light are extremely important. A scintillator is a substance that emits light when irradiated with radiation, and is used in positron annihilation tomography (PET) equipment and industrial applications in addition to the aforementioned radiation measurement applications and accelerator facilities such as heavy ion radiotherapy. Materials such as ZnS:Ag, Cu, etc. are widely used in conventional α-ray measuring instruments due to their luminous efficiency (see Patent Document 1, Patent Document 2, or Non-Patent Document 1).
Japanese Patent Application Laid-Open No. 2007-70496 JP 2010-127862 A Transactions of the Materials Research Society of Japan, 2013, Vol.38, No.3, p.443-446

However, existing scintillator materials (ZnS:Ag, Cu) widely used in conventional scintillator-type charged particle (α-ray) detectors are not recommended for use at temperatures above about 100°C. When installed in a high-temperature environment exceeding 10 degrees Celsius for a long time, there was a problem that the dose due to charged particles could not be measured for a long time, and the measured dose could not be measured accurately. . Therefore, conventional scintillator materials such as ZnS:Ag, Cu are not suitable for radiation measurement in nuclear facilities, which are expected to be used in high-temperature environments.

In addition, ZnS:Ag, Cu, etc. have the problem that the emission intensity is significantly deteriorated by high-density radiation, and frequent replacement is required. That is, in beam monitor measurement applications such as charged particle beams generated from accelerator facilities, a high-density ion flow is assumed, and existing scintillator materials (ZnS: Ag, Cu) have a significant attenuation in the amount of emitted light. If the integrated amount exceeds 10 ¹⁵ ions (hereinafter expressed as 10 ¹⁵ [ions/cm ² ]), replacement is required. Moreover, even in the previous measurements, it was necessary to take into consideration the deterioration of the luminous efficiency in obtaining the irradiation dose from the luminescence amount, so there was a problem that accurate measurement could not be performed.

As described above, conventional scintillator materials such as ZnS:Ag, Cu have an adverse effect on radiation dosimetry due to deterioration of emission intensity caused by radiation in nuclear facilities, which poses a problem in terms of reliability. In medical equipment such as heavy ion radiotherapy facilities that utilize this technology, frequent replacement is required due to deterioration in emission intensity due to high-density charged particle irradiation. Therefore, conventional radiation measuring instruments using scintillator materials still have problems in terms of deterioration in performance of beam quality and deterioration in operating efficiency of the accelerator apparatus due to deterioration in work efficiency resulting from replacement procedures. These problems are related to radiation measuring equipment that measures α-rays used in nuclear facilities, advanced medical equipment that uses radiation generators such as heavy ion radiotherapy equipment, and other accelerator facilities that use charged particles. Improvements are required in various fields ranging from basic/applied physics to industrial equipment with compact acceleration mechanisms such as ion implanters.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a charged particle radiation measuring method, a scintillator, and a charged particle radiation measuring apparatus with high heat resistance and radiation resistance.

The present invention is a charged particle radiation measurement method using a scintillator containing a phosphor whose main component is a nitride phosphor.

The present invention is a scintillator containing a phosphor whose main component is a nitride phosphor.

The present invention includes a scintillator containing a phosphor mainly composed of a nitride phosphor, an optical component that selectively collects light from the scintillator, and a measurement unit that reads the light condensed by the optical component. It is a charged particle radiation measurement device.

In the present invention, the nitride phosphors are CaAlSiN ₃ :Eu phosphor (CASN phosphor), (Sr, Ca)AlSiN ₃ :Eu phosphor (SCASN phosphor) and (Mg, Ca, Sr, Ba) ₂ It preferably contains one or more selected from Si ₅ N ₈ :Eu phosphors (258 phosphors).

According to the present invention, it is possible to provide a charged particle radiation measuring method, a scintillator, and a charged particle radiation measuring device with high heat resistance and radiation resistance.

1 is a schematic configuration diagram of a radiation dosimetry device according to an embodiment of the present invention, and is a schematic diagram of a system for measuring (1) spectrum and (2) emission intensity of scintillation light generated during ion irradiation. It is an example of the wavelength measurement result in the radiation dose measuring device of one embodiment. It is an example of the result of testing the radiation tolerance of the radiation dosimetry device with high-density radiation.

An embodiment of the present invention will be described in detail below. The present invention is not limited to the following embodiments, and can be implemented with appropriate modifications within a range that does not impair the effects of the present invention.

[Charged particle radiation measurement method]
(Phosphor)
The charged particle radiation measurement method according to the present embodiment uses a scintillator containing a phosphor whose main component is a nitride phosphor. "Main component" means that it is contained in the phosphor in an amount of 85% by mass or more, preferably 95% by mass or more.

The nitride phosphor contains at least one element selected from the group consisting of Be, Mg, Ca, Sr, and Ba and at least one element selected from the group consisting of C, Si, Ge, Sn, Ti, Zr, and Hf. and at least one element selected from the group consisting of Y, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, and Lu. Phosphor that is activated. The nitride phosphor may be an oxynitride phosphor that further contains oxygen. Since the phosphor containing the nitride phosphor as a main component is contained, a charged particle radiation measurement method with high heat resistance and radiation resistance can be obtained.

Nitride phosphors include CaAlSiN ₃ :Eu phosphor (CASN phosphor), (Sr, Ca)AlSiN ₃ :Eu phosphor (SCASN phosphor), (Mg, Ca, Sr, Ba) ₂ Si ₅ N ₈ : It preferably contains one or more selected from Eu phosphors (258 phosphors). The notation "(Sr, Ca)" means a composition containing one or two selected from Sr and Ca, and "(Mg, Ca, Sr, Ba)" means that the composition contains one or more selected from Mg, Ca, Sr and Ba. Also, ":Eu" means activated by Eu. When these nitride phosphors are contained, compared with existing scintillator materials such as ZnS:Ag, Cu phosphors, deterioration of the nitride phosphors due to high-temperature environments and high-density radiation irradiation is extremely unlikely to occur.

The shape of the nitride phosphor is not particularly limited, and shapes such as powder, sintered body, single crystal, and thin film can be used. In the case of powder, its size is usually 0.1 μm to 100 μm as an average primary particle size. The average primary particle size is a value measured with a laser diffraction/scattering particle size distribution analyzer. In the case of sintered bodies, the size can be from 1 μm to 500 μm.

These nitride phosphors can be obtained by adjusting the particle size and sintering commercially available products manufactured for white LEDs.

The phosphor may contain phosphors other than the nitride phosphor. Other phosphors include α-Sialon:Eu and β-Sialon:Eu.

(charged particle radiation)
The charged particle radiation measurable in this embodiment may be any of α-rays, β-rays, proton beams and heavy particle beams. In particular, it is possible to accurately and long-term measure the dose and energy of charged particle radiation that exists in a high-temperature environment or an environment in which high-density irradiation is performed.

[Charged particle radiation measuring device]
A charged particle radiation measuring device (hereinafter also referred to as a "radiation measuring device") according to the present embodiment includes a scintillator containing a phosphor mainly composed of a nitride phosphor, and selectively condensing light from the scintillator. and a measurement unit for reading light condensed by the optical component (light caused by radiation).

(scintillator)
The scintillator contains a phosphor whose main component is a nitride phosphor. Nitride phosphors and phosphors containing nitride phosphors as a main component are as described above, and are not described here. As a new scintillator material, which is a radiation-to-light conversion material, by using a phosphor whose main component is a nitride phosphor, the light from the scintillator material, the mechanical parts that hold and fix it, and the scintillator are selectively focused. It is possible to provide a radiation measuring device having high heat resistance and radiation irradiation resistance, which is composed of an optical component that performs measurement and a measurement unit that reads radiation-induced light.

The method for producing the scintillator is not particularly limited. For example, a phosphor containing a nitride phosphor as a main component is dispersed in water glass, an organic solvent, a resin, or the like, and then the dispersion is mixed with carbon, resin (polyimide, It can be carried out by uniformly applying it on a plate made of polycarbonate, etc., or fixing it in a resin sheet. The thickness of the scintillator is preferably 10 μm to 3000 μm, more preferably 50 μm to 500 μm. With this range, it is possible to efficiently measure radiation while suppressing the amount of the expensive nitride phosphor used.

The emission wavelength can be adjusted by the composition of the nitride phosphor constituting the scintillator, thereby improving the reading efficiency of the measuring instrument. In the radiation measuring apparatus according to the present embodiment, the spectrum of light emitted from the nitride phosphor with high heat resistance and radiation resistance due to radiation is measured with a peak wavelength (for example, 500 nm to 800 nm). For example, the emission wavelength can be adjusted within the above range by adjusting the composition of the nitride phosphor.

(optical parts)
The optical component selectively collects light from the scintillator. The optical component is not particularly limited as long as it can collect light of a specific wavelength. device (for example, manufactured by Hamamatsu Photonics, device name: PMA-11; manufactured by Spectra Corp., device name: SolidLambdaCCD).

(Measuring part)
The measurement unit reads the light caused by the radiation by reading the light condensed by the optical component. The measurement unit is usually composed of a computing terminal having a function of analyzing measured spectrum data, and an A/D conversion mechanism or the like for taking in the output of the photodetector as digital data as necessary. The light collected by the optical component is the light resulting from the radiation.

FIG. 1 is an example of a schematic configuration diagram showing a radiation measuring device. This radiation measuring apparatus uses radiation (proton microbeam) from an accelerator facility as primary radiation. When radiation strikes a scintillator (scintillator target), the scintillator emits light. The optical component selectively collects light from the scintillator. FIG. 1 shows an example in which a spectroscope that selectively collects light with a wavelength of 200 nm to 950 nm is used as an optical component. A measuring unit (photon counting unit) reads light resulting from the radiation condensed by the optical component using a computing terminal or the like, and outputs it as necessary.

A more specific configuration of the radiation measuring device is a mechanical part such as a holder that holds and fixes nitride phosphors in the form of powder, sintered body, single crystal, thin film, etc.; Optical parts for focusing light, camera equipment for reading photons caused by primary radiation, Avalanche Photo-Diode (APD), Photomultiplier (PMT), CCD element, Photodiode: PD), etc. can be combined.

α-rays such as environmental radiation do not originate from one point, but are generated from four sides surrounding the scintillator material. A configuration similar to that of FIG. 1 may be used.

Since the mechanical parts, optical parts, and measuring section need to have a geometric structure and arrangement suitable for the object to be measured, the structure may take various forms depending on the purpose. The measurement unit can change the observation mode by using a one-dimensional or two-dimensional measuring device.

According to the radiation measuring device according to the present embodiment, although the structure of the radiation measuring device is different, basically the same constituent elements can be used to measure radiation from a radiation source other than the radiation generator. It is possible to measure charged particles at

Conventional measuring instruments have a problem with the heat resistance of the members used, but the nitride phosphor used in this embodiment does not easily change structurally even at high temperatures. Therefore, it is possible to improve the operating temperature range of the radiation measuring instrument with higher radiation tolerance than before. As a result, it is possible to extend the life of alpha-ray measuring equipment for the purpose of normal radioactive contamination inspection, and realize radiation measuring equipment for alpha-ray measurement inside nuclear facilities and other places that require high temperature resistance.

(Application)
The charged particle radiation measuring method and the charged particle radiation measuring device according to the present embodiment are: (a) radiation measuring equipment that measures α-rays used in nuclear facilities and that performs measurement by a scintillation method; Beam monitors and radiation detectors for beam quality measurement in radiation generators (accelerators) such as particle beam and proton beam therapy equipment, c) Other accelerator facilities related to charged particle utilization, and compact equipment such as industrial ion implanters It can be used for a beam quality measuring device or the like in industrial equipment having an acceleration mechanism.

As described above, according to the charged particle radiation measurement method and the charged particle radiation measurement device according to the present embodiment, the temperature of about several hundred degrees (° C.) and the focused charged particle irradiation are difficult to use with the conventional charged particle radiation measurement equipment. It is possible to provide a radiation measuring device that can measure the dose of charged particles regardless of the conditions of high radiation dose such as the environment and that can be used for a longer life than before.

EXAMPLES The present invention will be described in more detail with reference to examples below, but the interpretation of the present invention is not limited by these examples.
(Example 1)
CaAlSiN ₃ : Eu powder (RE-650XMD grade manufactured by Denka Co., Ltd., CaAlSiN ₃ , average particle size: 15 μm) is dispersed in water glass and applied to a carbon plate in a coating thickness of 100 μm or less to uniformly fix. , produced a scintillator. This scintillator was attached to a radiation measuring apparatus as shown in FIG. 1, and a charged particle irradiation test was conducted.

A local (50 μm×50 μm) target was continuously irradiated with a 3 MeV H ⁺ (proton) focused ion beam from an adjacent accelerator facility at an irradiation density of 0.02 μA/mm ² .

(Comparative example 1)
A charged particle irradiation test was performed under the same conditions as in Example 1, except that the CaAlSiN ₃ :Eu powder was replaced with a ZnS:Ag phosphor powder.

FIG. 2 shows the measurement results of the spectrum and emission intensity at the start of the test of Example 1 and Comparative Example 1. As shown in FIG. Under the same irradiation dose, at the start of the test, in Example 1 using the CaAlSiN ₃ :Eu phosphor, charged-particle-excited luminescence with a comparable emission intensity on the longer wavelength side than Comparative Example 1 using ZnS:Ag. was observed. The CaAlSiN ₃ :Eu phosphor emission wavelength has the advantage of a higher quantum efficiency of the photosensor compared to that of ZnS:Ag.

FIG. 3 shows the results of the high-density irradiation test in Example 1 and Comparative Example 1 of the radiation measuring instrument. The horizontal axis indicates the irradiation time, and the vertical axis indicates the emission intensity at the same radiation irradiation intensity. From the irradiation time, the dose of charged particles can be measured using Equation I below.
Irradiation dose (ions/cm ² ) = Irradiation density (μA/mm ² ) x Irradiation time (sec) ÷ 1.602 x 10 ¹⁵ ) I

As is clear from FIG. 3, the luminous intensity of Comparative Example 1 using ZnS:Ag significantly attenuated as the irradiation amount of charged particles increased with an increase in irradiation time. On the other hand, in the case of Example 1 using the CaAlSiN ₃ :Eu phosphor, no attenuation of the emission intensity was observed, confirming that the high-density irradiation did not deteriorate the fluorescence characteristics.

From the above results, it can be seen that the charged particle radiation measurement method using the nitride phosphor of the present invention can be sufficiently used for radiation measuring instruments with high heat resistance and radiation resistance. Therefore, it is possible to measure the irradiation intensity and irradiation amount of radiation from the emission intensity over a long period of time from the output of the measurement unit of the radiation measuring device using the CASN phosphor.

In this example, the radiation from the accelerator facility is used as the radiation source, so the measurement time is remarkably accelerated and the test takes several hours. means high. CASN-based nitrides maintain their fluorescent properties even under conditions where charged particles continue to locally heat them, so they can be used in high-temperature environments of several hundred degrees (° C.).

Claims (3)

Using a scintillator containing a phosphor containing 85% by mass or more of a nitride phosphor,
The nitride phosphors are CaAlSiN ₃ :Eu phosphor (CASN phosphor), (Sr, Ca)AlSiN ₃ :Eu phosphor (SCASN phosphor) and (Mg, Ca, Sr, Ba) ₂ Si ₅ N ₈ : A charged particle radiation measurement method including one or more selected from Eu phosphors (258 phosphors). including a phosphor containing 85% by mass or more of a nitride phosphor,
The nitride phosphors are CaAlSiN ₃ :Eu phosphor (CASN phosphor), (Sr, Ca)AlSiN ₃ :Eu phosphor (SCASN phosphor) and (Mg, Ca, Sr, Ba) ₂ Si ₅ N ₈ : A scintillator for charged particle radiation measurement , containing one or more selected from Eu phosphors (258 phosphors). a scintillator containing a phosphor containing 85% by mass or more of a nitride phosphor;
an optical component that selectively collects light from the scintillator;
a measurement unit that reads the light condensed by the optical component,
The nitride phosphors are CaAlSiN ₃ :Eu phosphor (CASN phosphor), (Sr, Ca)AlSiN ₃ :Eu phosphor (SCASN phosphor) and (Mg, Ca, Sr, Ba) ₂ Si ₅ N ₈ : A charged particle radiation measurement device containing one or more selected from Eu phosphors (258 phosphors).

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