JP7624175B2 - Phosphor, its manufacturing method, and alpha ray detector - Google Patents

Description

The present invention relates to a phosphor, a method for producing the phosphor, and an alpha ray detector.

At nuclear power plants and other facilities, radiation emitted from waste containing radioactive materials and from radioactively contaminated equipment can be divided into three types: alpha rays, beta rays, and gamma rays. In order to evaluate environmental pollution caused by these types of radiation, radiation detectors equipped with scintillators are needed. Scintillators are a group of materials that emit light, mainly in the visible light range, when exposed to radiation, and are also used in photoelectric conversion elements such as photomultiplier tubes.

Since alpha rays have a strong interaction with matter, when they enter a scintillator layer that is several microns to several tens of microns thick, their progression is completely blocked inside. On the other hand, since gamma rays have a high penetrating power, they cannot be completely blocked even by a scintillator layer that is several microns thick, and the thickness required to block them is on the order of several tens to several hundred microns. Therefore, for example, if alpha rays and gamma rays simultaneously enter a scintillator layer that is several hundred microns thick, both will be blocked within the scintillator layer, and light will be emitted from both the alpha and gamma rays.

It is difficult to distinguish and measure alpha rays and gamma rays using a single survey meter when radiation is emitted from objects of unknown nuclide, such as radioactive waste. Therefore, when the radiation incident on the scintillator layer contains both alpha rays and gamma rays, the luminescence originating from alpha rays and the luminescence originating from gamma rays must be detected using separate corresponding survey meters. However, for example, at a site of radiation contamination where an emergency is required, using multiple types of survey meters is technically difficult and an economic burden. Therefore, there is a demand for technology that makes it possible to identify and distinguish the type of radiation as alpha rays using a single survey meter.

JP 2016-164210 A JP 2019-119798 A

S.Witkiewicz-Lukaszek, V.Gorbenko, T.Zorenko, O.Sidletskiy, P.Arhipov, A.Fedorov, J.A.Mares, R.Kucerkova, M.Nikl, and Y.Zorenko: CrystEngComm 22 (2020) 3713-3724 .

As a scintillator layer for detecting radiation, a single crystal having a homogeneous structure is used in order to obtain high luminous efficiency (Patent Documents 1 and 2). A single crystal is obtained by processing a single crystal ingot formed by a melt solidification method to a specified thickness, and it is difficult to make the thickness of the obtained single crystal less than 50 μm.

By using the liquid phase epitaxy method, it is possible to synthesize a scintillator layer made of a single crystal with a thickness of 50 μm or less. However, since it is difficult to avoid the inclusion of impurity elements during the synthesis process, a single crystal formed with a thickness of 50 μm or less does not emit a sufficient amount of light due to the influence of the impurity elements.

Using common thin-film deposition methods such as sputtering, it is difficult to form single crystals with a thickness of 5 μm or more, and single crystals formed using this method are too thin to block the progression of alpha rays, making it difficult to obtain sufficient light emission from alpha rays.

In Non-Patent Document 1, a two-layer structure is used to discriminate alpha rays by discriminating between alpha rays on the front side and gamma rays on the rear side when viewed from the direction of radiation incidence, but in this case the photodetector is limited to measuring single photons using photomultiplier tubes or photodiodes, and the spatial resolution is limited to about 1 mm or better. Furthermore, there are problems such as the circuitry at the rear of the photodetector becoming complicated in order to discriminate between gamma rays, making analysis cumbersome.

The present invention was made in consideration of the above circumstances, and aims to provide a phosphor that enables discriminative measurement of alpha rays, a method for manufacturing the phosphor, and an alpha ray detector.

To solve the above problems, the present invention adopts the following measures.

(1) A phosphor according to one aspect of the present invention is a phosphor used for radiation detection, characterized in that it comprises a scintillator layer and a substrate layer as defined below. That is, it comprises a scintillator layer having a thickness of 5 μm or more and 30 μm or less, and having transparency to visible light generated by irradiation with α-rays. In addition, it comprises a substrate layer, which is different from the scintillator layer and does not emit light due to radiation, downstream of the scintillator layer when radiation is incident.

(2) In the phosphor described in (1) above, it is preferable that the scintillator layer is made of a material with an effective atomic number of 10 to 75 and has a thickness of 5 μm to 30 μm.

(3) In the phosphor described in (1) or (2), it is preferable that the scintillator layer is composed of multiple phases including a main phase of a single crystal structure, and the main phase has a volume of 50% or more of the total.

(4) In the phosphor described in any one of (1) to (3), it is preferable that the scintillator layer contains an activator element in a ratio of 0.01 mol % to 20 mol %.

(5) In the phosphor described in any one of (1) to (4), it is preferable that the main phase of the scintillator layer has one or a combination of two or more of the following structures: garnet structure, bixbyite structure, perovskite structure, cuspidine structure, orthosilicate structure, pyrosilicate structure, and pyrochlore structure.

(6) An α-ray detector according to one aspect of the present invention includes a position-sensitive detector that detects only the visible light, disposed downstream of the phosphor described in any one of (1) to (5) above, with respect to the incidence of radiation, and discriminates only the α-rays from among two or more types of radiation including α-rays, without discriminating the radiation on an event-by-event basis. Examples of the position-sensitive detector include, but are not limited to, a CCD or CMOS sensor.

(7) A method for producing a phosphor according to one aspect of the present invention is a method for producing a phosphor according to any one of (1) to (6), in which the scintillator layer is formed on one surface of the substrate layer using a laser CVD method.

The phosphor of the present invention has a scintillator layer with a thickness of 5 μm to 30 μm, which allows highly penetrating radiation such as gamma rays to pass through while blocking the progress of only alpha rays within the scintillator layer. Therefore, only visible light originating from alpha rays is emitted within the scintillator layer when exposed to radiation. Since the scintillator layer is transparent to this visible light, it can be detected from outside the phosphor, and discrimination measurement of alpha rays can be performed based on the detection results without discriminating between radiation such as gamma rays.

FIG. 1 is a cross-sectional view showing a schematic configuration of a laser CVD apparatus used for producing a phosphor of the present invention. 1 is an example of a conceptual diagram of an alpha ray detector. 4A and 4B are SEM images of the cross section and the surface of the phosphor of Example 1. 1 is a graph showing the light emission characteristics of the phosphor of Example 1. 1 is a graph showing the light emission characteristics of phosphors of Example 1 and Comparative Example 1.

The phosphor according to the embodiment of the present invention and its manufacturing method will be described in detail below with reference to the drawings. Note that the drawings used in the following description may show characteristic parts in an enlarged scale for the sake of convenience in order to make the characteristics easier to understand, and the dimensional ratios of each component may not necessarily be the same as in reality. In addition, the materials, dimensions, etc. exemplified in the following description are merely examples, and the present invention is not limited to them, and can be modified as appropriate within the scope of the present invention.

First Embodiment
(Phosphor)
The phosphor according to the first embodiment of the present invention is a phosphor used for radiation detection, and includes a scintillator layer made of a substance that emits light mainly in the visible light range when irradiated with radiation. The scintillator layer has a thickness of 5 μm to 30 μm, which is suitable for absorbing α-rays and transmitting high-energy radiation such as γ-rays.

If the thickness of the scintillator layer is less than 5 μm, a sufficient amount of light may not be obtained, and the irradiated α-rays will pass through the scintillator layer, so the light emission from α-rays necessary for discriminating α-rays will not occur. If the thickness of the scintillator layer exceeds 30 μm, not only α-rays but also gamma rays will be absorbed by the scintillator layer, so light emission from gamma rays will occur in addition to light emission from α-rays.

The absorption rate of irradiated radiation is affected by the effective atomic number of the constituent material. Therefore, from the viewpoint of increasing this absorption rate, for example, when the scintillator layer is made of a material with an effective atomic number of 10 to 50, it is preferable that the layer has a thickness of 8 μm to 30 μm. Also, when the scintillator layer is made of a material with an effective atomic number of 50 to 75, it is preferable that the layer has a thickness of 5 μm to 25 μm.

The scintillator layer has a degree of transparency to visible light generated by irradiation with alpha rays, preferably 10% to 90%, to a degree that allows detection by a specified detection device. From the viewpoint of increasing the transparency of visible light, it is preferable that the layer has an orientation degree of 50% or more of that of a single crystal structure, and it is most preferable that the layer has a single crystal structure. As long as the transparency of visible light is not too low, the scintillator layer may have a structure consisting of multiple phases including a main phase of a single crystal structure. However, it is preferable that the main phase of the single crystal occupies 50% or more of the total volume. It is preferable that the scintillator layer has one or a combination of two or more of the following structures: garnet structure, bixbyite structure, perovskite structure, cuspidine structure, orthosilicate structure, pyrosilicate structure, and pyrochlore structure.

The scintillator layer may have a garnet structure represented by _A3B5O12 , and preferably a complex phase _in which different crystal phases including an oxide represented by _B2O3 are simultaneously present. The scintillator layer may also have a _{bixbyite structure represented by A2O3 , a} perovskite structure represented by _ABO3 , or a _cuspidine structure represented by _A4B2O9 . In these cases, A may be one _or a combination of two or more of, for example, Gd, Sc, Y, _Tb , Dy, Ho, Er, Tm, Yb, and Lu, and B may be one or a combination of two or more of, for example, Al and Ga.

The scintillator layer _{may simultaneously contain different crystal phases including a bixbyite structure represented by A2O3, and preferably oxides represented by B2O3, A3B5O12, and A4B2O9 as a multiple phase . In these} cases, A may be one or a combination of two or more of, for example, Gd, Sc, Y, Tb, Dy, Ho, _Er , _Tm , Yb, and Lu, and B may be one or a combination of two or more of, for example, Al and Ga.

The scintillator layer may simultaneously have different crystal phases including an orthosilicate structure represented by _A2BO5 , preferably _an oxide represented by _A2O3 as a multiple phase. In this case, A may be one or a combination of two or more of Gd, Y, _Yb , and Lu, and B may be, for example, Si.

The scintillator layer may have a perovskite structure represented by _ABO3 , and preferably may simultaneously have different crystal phases including an oxide represented by _BO2 as a multiple phase. In the case of the perovskite structure, A may be, for example, one or a combination of two or more of Ca, Sr, Ba, and Pb, and B may be, for example, one or a combination of two or more of Ti, Zr, and Hf.

The scintillator layer may have a pyrosilicate structure represented by A ₂ B ₂ O ₇ or a pyrochlore structure, preferably a complex phase including an oxide represented by BO _2, and may simultaneously have different crystal phases. In the case of the pyrosilicate structure, A may be, for example, one or a combination of two or more of Gd, Y, Yb, and Lu, and B may be, for example, Si. In the case of the pyrochlore structure, A may be, for example, one or a combination of two or more of Gd, Sc, Y, Tb, Dy, Ho, Er, Tm, Yb, and Lu, and B may be, for example, one or a combination of two or more of Ti, Zr, and Hf.

The scintillator layer preferably contains an activator element in a ratio of 0.01 mol % to 20 mol %. The activator element may be, for example, one or a combination of two or more of Ce3 ⁺ , Pr3 ⁺ , Nd3 ⁺ , Sm3 ^{+, Eu3+ ,} Tb3 ⁺ , Dy3 ⁺ , Ho3 ⁺ , Er3 ⁺ , Tm3 ⁺ , Yb3 ⁺ , and Eu2 ⁺ .

The scintillator layer may contain 1000 ppm or less of alkali metals or alkaline earth metals such as Mg ²⁺ , Ca ²⁺ , Sr ²⁺ , Ba ²⁺ , Li ⁺ , Na ⁺ , and K ⁺ for the purpose of adjusting the charge balance or preventing crystal defects. Elements other than these may also be added for the same purpose.

(Method of manufacturing phosphor)
1 is a cross-sectional view showing a schematic configuration example of a laser CVD apparatus 100 used for producing a phosphor according to this embodiment. The laser CVD apparatus 100 is mainly composed of a chamber 101, a substrate support section 102 that supports a substrate 10 in the chamber 101, a laser light irradiation section 103 that irradiates the substrate 10 with a laser light, and a source gas supply section 104 that supplies a source gas into the chamber 101.

The substrate support section 102 is mainly composed of a stage 102A on which the substrate 10 is placed, and a thermocouple 102B attached to the stage 102A and used to monitor the temperature of the substrate 10.

The laser irradiated by the laser light irradiation unit 103 may be, for example, a carbon dioxide laser, a semiconductor laser, or a solid-state laser.

The raw material gas supply unit 104 is mainly composed of heater chambers 104B, 104D that heat and vaporize the precursor of the phosphor raw material to produce raw material gas, carrier gas (Ar gas) supply sources (supply units) 104A, 104C, a nozzle 104E that introduces the raw material gas and carrier gas into the chamber 101, an oxygen gas supply source (supply unit) 104F, and a nozzle 104G that introduces the supplied oxygen gas into the chamber 101.

For example, when producing a phosphor made of LuAG, one heater chamber 104B functions as a supply source of lutetium dispivaloylmethanato (Lu(dpm) ₃ ), and the other heater chamber 104D functions as a supply source of aluminum trisacetylacetonato (Al(acac) ₃ ). The number of heater chambers may be increased or decreased depending on the number of raw materials required.

Carrier gas supply sources 104A and 104C are connected to heater chambers 104B and 104D, respectively, and are configured so that the supplied carrier gas passes through heater chambers 104B and 104D and transports the raw material gas vaporized in heater chambers 104B and 104D into chamber 101. Carrier gas supply sources 104A and 104C and oxygen gas supply source 104F each include a mass flow controller that adjusts the flow rate of the gas supplied.

The method for manufacturing a phosphor has the following steps. First, the substrate 10 is placed on the stage 102A, and the chamber 101 is evacuated to a pressure suitable for film formation (evacuation step). Next, the laser light irradiation unit 103 is used to irradiate the substrate 10 with laser light L to heat the substrate 10 (substrate heating step). Then, the raw material gas is supplied to the heated substrate 101 together with the carrier gas, thereby forming a phosphor film (phosphor film formation step).

When multiple types of raw material gases are supplied in the phosphor film formation process, the content ratio (composition ratio) of the various raw materials in the phosphor to be formed can be adjusted by adjusting the content ratio. In addition, the thickness of the phosphor to be formed can be adjusted by adjusting the time for supplying the raw material gases, i.e., the film formation time.

As described above, the phosphor of the first embodiment has a scintillator layer having a thickness of 5 μm or more and 30 μm or less, and is capable of transmitting highly penetrating radiation such as gamma rays while blocking (absorbing) the progression of only alpha rays within the scintillator layer. Therefore, only visible light originating from alpha rays is emitted within the scintillator layer when irradiated with radiation. Since the scintillator layer is transparent to this visible light, it can be detected from outside the phosphor, and discrimination measurement of alpha rays can be performed based on the detection results.

When using the melt solidification method to manufacture phosphors, it is difficult to achieve a thickness of 5 μm or more and 30 μm or less, but this is possible by using the laser CVD method of this embodiment. In addition, when using the laser CVD method of this embodiment, it is possible to avoid the problem of the liquid phase method in which impurity elements such as transition metals and alkali metals are mixed in, and it is possible to achieve a high light emission amount that is not affected by impurity elements. Even when the phosphor is thin, it is possible to obtain the light emission amount necessary to discriminate alpha rays, making it possible to thin it to the range of 5 μm or more and 30 μm or less, which allows gamma rays to pass through.

Second Embodiment
The phosphor according to the second embodiment of the present invention is a phosphor used for radiation detection, and includes a scintillator layer on the front side in the direction of incidence of radiation, and a substrate layer on the rear side. The substrate layer has a thickness of 5 μm or more and 20 mm or less, is made of a material different from that of the scintillator layer, and is transparent to visible light generated in the scintillator layer. The substrate layer is laminated (bonded) to the scintillator layer directly or with an intermediate layer sandwiched therebetween. The configuration of the scintillator layer is the same as that of the phosphor of the first embodiment, and discriminative measurement of α-rays can be performed.

The phosphor of this embodiment is obtained by using the above-mentioned substrate layer as a base material and forming a scintillator layer on one side of the substrate layer using a laser CVD method, as in the first embodiment. There is no limitation on the order in which the two layers are stacked, and the substrate layer may be fabricated first and the scintillator layer may be crystal-grown thereon, or the scintillator layer may be fabricated first and the substrate layer may be crystal-grown thereon. In either case, from the viewpoint of assisting crystal growth, it is preferable that the scintillator layer and the substrate layer are made of materials having similar crystal structures.

In this embodiment, it is assumed that there are two scintillator layers with different thicknesses, but the number of scintillator layers is not limited, and three or more scintillator layers may be provided to discriminate radiation other than alpha rays and gamma rays.

In the phosphor of this embodiment, the scintillator layer having a thickness of 5 μm or more and 30 μm or less absorbs only α-rays, and the substrate layer having a thickness of 5 μm or more and 20 mm or less can absorb radiation that has passed through the scintillator layer. For example, when the substrate layer has a thickness of 50 μm or more and 20 mm or less, it can absorb γ-rays.

Figure 2 is a schematic diagram showing the configuration of an α-ray detector 200 to which the phosphor of this embodiment is applied. The α-ray detector 200 is composed of a phosphor having a scintillator layer 201 on the front side in the direction of incidence of radiation, a substrate layer 202 on the rear side, and a position-sensitive photodetector 203 that detects only visible light arranged on the rear side of the phosphor. The position-sensitive detector is not particularly limited, but examples include image sensors such as CCD and CMOS sensors composed of multiple pixels. Visible light generated in the scintillator layer 201 by irradiation with α-rays passes through the substrate layer 202 and reaches the position-sensitive photodetector 203. Radiation such as gamma rays other than α-rays passes through the scintillator layer 201 and is absorbed by the substrate layer 202 or passes through the substrate layer 202. Here, the area and shape in which light is emitted in 201 for each radiation are characteristic. For example, since alpha rays have a range of about several microns, the range in which light is emitted is roughly symmetrical with respect to the point of incidence of the alpha rays at 201, and is an area of about several microns. On the other hand, the signal generated when gamma rays are incident on 203 becomes pixel noise. Therefore, when multiple events are measured simultaneously, alpha rays can be discriminated by 203.

The combination of the phosphor and the position-sensitive photodetector is configured, for example, as shown in FIG. 2, and when the magnitude of the signal from the position-sensitive photodetector 203 is equal to or greater than a certain level, it is discriminated as a signal in the scintillator layer 201. In addition, alpha rays and noise may be discriminated from the imaging results based on their spread. Note that the method of combination and analysis of the position-sensitive photodetector 203 is not limited to this.

The following examples will make the effects of the present invention clearer. Note that the present invention is not limited to the following examples, and can be modified as appropriate without departing from the spirit of the present invention.

Example 1
Using the above-mentioned manufacturing method of the phosphor, a scintillator layer having a main phase of LuAG (Lu ₃ Al ₅ O ₁₂ ) having a garnet structure and containing 9.0 mol % of Ce ³⁺ as an activation element was formed on one side of the substrate. The thickness of the scintillator layer was 5.2 μm. The effective atomic number was 62.9. The substrate was made of YAG (Y ₃ Al ₅ O ₁₂ ). The main manufacturing conditions of the scintillator layer were set as follows.
Laser power density: 79 W/ ^cm2
Ar gas flow rate: 100 sccm
Flow rate of oxygen gas: 100 sccm
Raw material vaporization temperature: 190 to 270°C
Film formation temperature: 970° C.
Film formation pressure: 200 Pa
Film formation speed: 62μm/h

(Comparative Example 1)
A scintillator layer having a main phase of Gd ₃ Al ₂ Ga ₃ O ₁₂ (GAGG), which is generally known as a scintillator crystal, and having Ce ³⁺ added as an activation element, was formed by melt solidification. The thickness of the formed scintillator layer was about 1 mm.

Figures 3(a) and (b) are SEM images of the cross section and surface of the phosphor formed in Example 1. It can be seen that a film with a uniform thickness of about 5 μm is formed as the scintillator layer. In addition, since the surface is uniform, it can be seen that the scintillator layer has a single crystal structure.

The scintillator layer of Example 1 was irradiated with 5.5 MeV α-rays, and the light emitted from the scintillator layer to the outside was measured to examine the emission spectrum. Figure 4 is a graph showing the measurement results. The horizontal axis of the graph indicates the emission wavelength [nm], and the vertical axis of the graph indicates the emission intensity. Since the emission spectrum has a peak near a wavelength of 500 nm in the visible light range, it is understood that light emission originating from Ce ³⁺ ions occurs, and that the irradiated α-rays are converted into visible light.

The scintillator layers of Example 1 and Comparative Example 1 were irradiated with radiation including alpha rays and gamma rays, and measurements were performed to examine the pulse height spectrum of the visible light converted within each scintillator layer. Figure 5 is a graph showing the measurement results. The horizontal axis of the graph indicates the digital channel value [ch] corresponding to the amount of light emitted, and the vertical axis of the graph indicates the light emission intensity.

The pulse height spectrum 401 of Comparative Example 1 has both a peak in the energy region of 200 ch or less, which indicates a response to gamma rays, and a peak in the energy region of 1000 to 1200 ch, which indicates a response to alpha rays. Therefore, in the scintillator layer of Comparative Example 1, light emission originating from both alpha rays and gamma rays occurs, and it is clear that it is difficult to discriminate and measure alpha rays from this light emission.

On the other hand, the pulse height spectrum 402 of Example 1 does not have a peak in the energy region below 200 ch, and only has a peak in the energy region of 1000 to 1200 ch. Therefore, in the scintillator layer of Example 1, the light emission originating from gamma rays is suppressed and only the light emission originating from alpha rays is generated, and it is therefore possible to discriminate and measure alpha rays from this light emission.

Example 2
Using the above-mentioned manufacturing method of the phosphor, a scintillator layer having a garnet structure as the main phase and containing 9.0 mol% of Ce3 ⁺ as an activation element was formed on one side of the substrate. The thickness of the scintillator layer was set to 1.6, 2.1, 4.3, 9.7, and 22.2 _μm . The substrate was made of _Al2O3 .

The scintillator layer of Example 2 was irradiated with 5.5 MeV alpha rays, and an image was taken with a CCD camera to measure the intensity. The results are shown in Table 1. Cases where it was determined that a signal was detected are indicated with a circle, and cases where it was determined that a signal was not detected are indicated with an x. From this, it was found that a sufficient signal was not visible when the thickness was approximately 5 μm or less.

(Examples 3 to 13)
Using the above-mentioned manufacturing method of the phosphor, a scintillator layer having a main phase of Y ₂ O ₃ having a bixbyite structure, Lu ₂ O ₃ having a bixbyite structure, LuAP (LuAlO ₃ ) having a perovskite structure, and LuAG having a garnet structure, and doped with Eu ³⁺ , Nd ³⁺ , and Ce ³⁺ as dopant elements, was formed on one side of a substrate. The substrate used was made of YSZ (Y ₂ O ₃ -ZrO ₂ ), STO (SrTiO ₃ ), and YAG.

The scintillator layers of Examples 3 to 13 were irradiated with 5.5 MeV alpha rays, received by a photomultiplier tube, and the photoelectrons were counted. The results are shown in Table 2. The cases where it was determined that a signal was detected are indicated with a circle, and the cases where it was determined that a signal was not detected are indicated with an x. From this, it can be seen that when made of a material with an effective atomic number of 10 to 50, a signal can be detected at a thickness of 8 μm or more, and when made of a material with an effective atomic number of 50 to 75, a signal can be detected at a thickness of 5 μm or more. Therefore, it can be seen that the scintillator layer composed of the above-mentioned main phase and activation element can be used for discriminating and measuring alpha rays by having the above-mentioned range of additive concentration and film thickness.

100: Laser CVD apparatus 101: Chamber 102: Substrate support section 102A: Stage 102B: Thermocouple 103: Laser light irradiation section 104: Raw material gas supply section 104A: Carrier gas supply source (supply section)
104B: Heater chamber (source of raw material precursor)
104C: Carrier gas supply source (supply section)
104D: Heater chamber (source of raw material precursor)
104E: Raw material precursor gas supply nozzle 104F: Oxygen gas supply source 104G: Oxygen gas supply nozzle L: Laser light 200: Alpha ray detector 201: Scintillator layer 202: Substrate layer 203: Position sensitive photodetector 204: Alpha rays 205: Gamma rays 206: Light emission

Claims (7)

A phosphor for use in radiation detection, comprising:
a scintillator layer on a front side and a substrate layer on a rear side in a direction in which radiation is incident;
the scintillator layer has a thickness of 5 μm or more and 30 μm or less, and has an orientation degree of 50% or more of that in the case of a single crystal structure; and is transparent to visible light generated by irradiation with α-rays;
A phosphor, characterized in that the substrate layer is made of a material different from that of the scintillator layer and does not emit light in response to the radiation. The phosphor according to claim 1, characterized in that the scintillator layer is made of a material with an effective atomic number of 10 to 75 and has a thickness of 5 μm to 30 μm. The phosphor according to claim 1 or 2, characterized in that the scintillator layer is made up of multiple phases including a main phase of a single crystal structure, and the main phase has a volume of 50% or more of the entire phosphor. The phosphor according to any one of claims 1 to 3, characterized in that the scintillator layer contains an activator element in a ratio of 0.01 mol% to 20 mol%. The phosphor according to any one of claims 1 to 4, characterized in that the scintillator layer has one or a combination of two or more of the following structures: garnet structure, bixbyite structure, perovskite structure, cuspidine structure, orthosilicate structure, pyrosilicate structure, and pyrochlore structure. a position-sensitive photodetector for detecting only the visible light is disposed downstream of the phosphor according to any one of claims 1 to 5;
An α ray detector which does not discriminate the radiation on an event-by-event basis, but discriminates only the α rays from among the radiation. A method for producing the phosphor according to any one of claims 1 to 5, comprising the steps of:
A method for producing a phosphor, comprising forming the scintillator layer on one surface of the substrate layer by using a laser CVD method.

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