JP2010169674A - Radiation detector - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide high-sensitivity radiation detectors having superior energy resolution. <P>SOLUTION: The refractive index of a scintillator crystal 2 is not less than n1; the refractive index of a first light wavelength conversion layer 4, which is filled into a space between the scintillator crystal 2 and a photodetector 5, is less than n1 and not less than n2; and the refractive index of a second light wavelength conversion layer 3, which is filled into a space between the scintillator crystal 2 and a reflection member 9, is less than n2. Thus, the wavelength of scintillation light 6 is fitted to wavelength sensitivity of the photodetector 5 by the second light wavelength conversion layer 3, and the transmittance of the scintillator crystal 2 is transmitted effectively into a high wavelength. The scintillation light 6 is efficiently reflected, prior to reaching the first light wavelength conversion layer 4 and efficiently reaches the photodetector 5, without being reflected by the first light wavelength conversion layer 4. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a radiation detector that detects the incidence of radiation, and more particularly to a radiation detector that converts scintillation light generated in a scintillator crystal by the incidence of radiation into an electrical signal by a photodetector.

  Generally, a radiation detector is a scintillator crystal that receives radiation such as X-rays or γ-rays and converts it into visible light, and a photomultiplier tube that detects visible light converted and transmitted by the scintillator crystal and converts it into an electrical signal. (PMT), a photodiode (PD) or the like, a reflection member for efficiently guiding scintillation light emitted from the scintillator crystal to the photodetector, and the like.

  In addition to the function of absorbing radiation and converting it into light, the scintillator crystal is required to have transparency that allows the converted light to pass through to the light detection unit without being attenuated. In addition, the scintillator crystal material of the radiation detector must have a function as a scintillator crystal that absorbs radiation and emits light, and has a peak emission wavelength at a wavelength where the conversion efficiency of the detector to an electric signal is high. Is also important.

On the other hand, in a radiation detector that combines a scintillator crystal having a peak emission wavelength of 400 nm or less such as CsI or praseodymium-doped lutetium aluminate (Lu ₃ Al ₅ O ₁₂ : Pr) with a photodetector, light is emitted at a fluorescence wavelength of 400 nm or less. Since the conversion efficiency of the detector into an electrical signal is low, the light conversion efficiency and detection sensitivity of the radiation detector are reduced.

  Therefore, radiation detection is performed by forming an optical wavelength conversion layer between the scintillator crystal and the photodetector, which converts the wavelength of the scintillation light generated from the scintillator crystal made of a polycrystalline compound into a wavelength suitable for the wavelength sensitivity of the photodetector. There is a method for increasing the light conversion efficiency and detection sensitivity of the detector (for example, see Patent Document 1).

  In addition, an optical wavelength conversion layer that converts the wavelength of scintillation light into a wavelength suitable for the wavelength sensitivity of the photodetector is applied to two circular CsI surfaces cut into a cylindrical shape, and one of the surfaces is optically bonded to the photodetector. There is also a method of increasing the light conversion efficiency and detection sensitivity of the radiation detector (see, for example, Patent Document 2).

JP 2002-82171 A Japanese Patent Publication No. 07-78215

Nuclear Instruments and Methods in Physics Research A 486 (2002) 40-47

  In the technique described in Patent Document 1, a wavelength conversion layer is formed only between the scintillator crystal and the photodetector. A wavelength conversion layer is not formed on a surface other than the surface between the scintillator crystal and the photodetector.

  For this reason, the scintillation light is wavelength-converted on a surface other than the surface between the scintillator crystal and the photodetector, and is efficiently reflected and finally led to the photodetector, resulting in detection of the radiation detector. There is a problem that the sensitivity is not improved.

  In the technique described in Patent Document 2, the refractive index of the CsI scintillator crystal is 1.8 at the peak wavelength of light emission, and the refractive index of the light wavelength conversion layer is about 1.4 to 1.62. The difference in refractive index between the two is small.

  Therefore, even if the light wavelength conversion layer is formed between the scintillator crystal and the photodetector, the total reflection component of the scintillation light between the scintillator crystal and the light wavelength conversion layer is small, so that the light wavelength conversion layer is transmitted. The light enters the photodetector.

On the other hand, in a scintillator crystal whose base material is lutetium aluminate (Lu ₃ Al ₅ O ₁₂ ) having a refractive index of about 2.0, a light wavelength conversion layer having a refractive index of about 1.4 to 1.62 Is formed between the scintillator crystal and the photodetector, the difference in refractive index between the scintillator crystal and the surface of the photodetector is large. For this reason, the total reflection component of the scintillation light between the scintillator crystal and the light wavelength conversion layer increases, and there is a problem that the light conversion efficiency and the detection sensitivity of the radiation detector are lowered.

  The present invention has been made in view of the above problems, and provides a radiation detector having a simple structure and good light conversion efficiency and detection sensitivity.

  A radiation detector according to the present invention is a radiation detector for detecting the incidence of radiation, a scintillator crystal having a refractive index n1 (n1 is a specific real number) or more that generates scintillation light internally by the incidence of radiation, and a scintillator A photodetector arranged at a position facing the crystal and converting incident scintillation light into an electrical signal; and a gap between the scintillator crystal and the photodetector is filled with a refractive index of n2 (n2 is a real number less than n1) ) The first light wavelength conversion layer described above, a reflecting member that is disposed at a position facing a surface other than one surface of the scintillator crystal facing the photodetector and reflects incident scintillation light, and the scintillator crystal and the reflection A second light wavelength conversion layer filled in a gap with the member and having a refractive index of less than n2.

  Therefore, in the radiation detector of the present invention, scintillation light is generated when radiation enters the scintillator crystal, and the scintillation light is converted into an electrical signal by the photodetector, thereby detecting the incidence of radiation. However, the refractive index of the scintillator crystal is n1 or more, the refractive index of the first light wavelength conversion layer filled in the gap between the scintillator crystal and the photodetector is n2 or more less than n1, and the scintillator crystal and the reflecting member The refractive index of the second light wavelength conversion layer filled in the gap is less than n2. For this reason, the wavelength of the scintillation light can be adapted to the wavelength sensitivity of the photodetector by the second light wavelength conversion layer, and can be effectively converted to a wavelength with high transmittance of the scintillator crystal. In addition, since the refractive index difference between the scintillator crystal and the second light wavelength conversion layer is sufficiently large, the scintillation light is efficiently reflected and then efficiently reaches the first light wavelength conversion layer. Since the refractive index difference between the scintillator crystal and the first light wavelength conversion layer is sufficiently small, the scintillation light efficiently reaches the photodetector without being reflected by the first light wavelength conversion layer.

  In the radiation detector as described above, the scintillator crystal has a peak wavelength of scintillation light of 400 nm or less and a refractive index n1 of 1.8 or more, and the first light wavelength conversion layer has a refractive index n2 of 1.62. The second light wavelength conversion layer is a radiation detector having a refractive index n2 of less than 1.62, and the second light wavelength conversion layer is made of a translucent resin in which phosphors are uniformly dispersed. It may be.

  In the radiation detector as described above, the first light wavelength conversion layer may be made of translucent porous glass in which phosphors are uniformly dispersed.

  In the radiation detector as described above, the phosphor is a coumarin compound, an oxazole compound, a phenyl compound, an oxadiazole compound, a rhodamine compound, a sulfodamine compound, a dicyanomethyl compound (DCM). Or at least one organic compound selected from styryl compounds and pyromethane compounds.

  In the radiation detector as described above, the scintillator crystal may be composed of praseodymium-added lutetium aluminate.

  Further, in the radiation detector as described above, the photodetector may be composed of a semiconductor light receiving element including a set of normal mode APD (Avalanche Photo Diode) or Geiger mode APD pixels.

  In the radiation detector of the present invention, the refractive index of the scintillator crystal is n1 or more, and the refractive index of the first light wavelength conversion layer filled in the gap between the scintillator crystal and the photodetector is n2 or more which is less than n1. The refractive index of the second light wavelength conversion layer filled in the gap between the scintillator crystal and the reflecting member is less than n2. For this reason, the wavelength of the scintillation light can be adapted to the wavelength sensitivity of the photodetector by the second light wavelength conversion layer, and can be effectively converted to a wavelength with high transmittance of the scintillator crystal. In addition, since the refractive index difference between the scintillator crystal and the second light wavelength conversion layer is sufficiently large, the scintillation light is efficiently reflected and then efficiently reaches the first light wavelength conversion layer. Since the refractive index difference between the scintillator crystal and the first light wavelength conversion layer is sufficiently small, the scintillation light efficiently reaches the photodetector without being reflected by the first light wavelength conversion layer. Therefore, the photoelectric conversion efficiency in the photodetector is greatly increased, the number of photons reaching the photodetector is increased, and the radiation detector has high sensitivity and excellent energy resolution.

It is a schematic diagram which shows the internal structure of the radiation detector of embodiment of this invention. It is a schematic diagram which shows the optical characteristic in a radiation detector. It is a characteristic view which shows the wavelength sensitivity (quantum conversion efficiency) of PMT and PD which are general photodetectors. Praseodymium added lutetium aluminate: is a characteristic diagram showing the emission spectrum and the transmission spectrum of _{(Lu 3 Al 5 O 12 Pr} ). It is a characteristic diagram showing the emission spectrum and the absorption spectrum of CeF _3. Lu ₃ Al ₅ O _12: is a graph showing the emission spectrum of the scintillator crystals made of Pr. It is a characteristic diagram showing the emission spectrum of the scintillator crystals made of CeF _3. It is a characteristic view which shows the various characteristics of Examples 1-5 and Comparative Example 1. It is a characteristic view which shows the various characteristics of Examples 6-10 and Comparative Example 2. It is a characteristic view which shows the various characteristics of Examples 11-15 and Comparative Example 3. It is a characteristic view which shows the various characteristics of Examples 16-20 and Comparative Example 4.

  An embodiment of the present invention will be described below with reference to the drawings. As shown in FIG. 1, the radiation detector 1 of the present embodiment is a radiation detector 1 that detects the incidence of radiation 8, and the peak wavelength of scintillation light 6 that is generated internally by the incidence of radiation 8 is 400 nm. A scintillator crystal 2 having a refractive index of 1.8 or more, a photodetector 5 that is disposed at a position facing the scintillator crystal 2 and converts incident scintillation light 6 into an electrical signal, and the scintillator crystal 2 and light detection And a first light wavelength conversion layer 4 having a refractive index of 1.62 or more.

  Further, a reflecting member 9 that is disposed at a position facing a surface other than one surface of the scintillator crystal 2 facing the photodetector 5 and reflects the incident scintillation light 6, and the scintillator crystal 2 and the reflecting member 9 And a second optical wavelength conversion layer 3 filled in the gap and having a refractive index of less than 1.62.

  In other words, the radiation detector 1 according to the present embodiment includes a scintillator crystal 2 having a refractive index n1 (n1 is a specific real number) or more that generates scintillation light 6 when radiation 8 is incident, and the scintillator crystal 2 and light. The gap between the detector 5 and the first light wavelength conversion layer 4 having a refractive index of n2 (n2 is a real number less than n1) or more, and the gap between the scintillator crystal 2 and the reflecting member 9 is filled and refracted. A second light wavelength conversion layer 3 having a rate of less than n2.

As will be described in detail later, the scintillator crystal 2 is made of praseodymium-added lutetium aluminate containing, for example, lutetium aluminate (Lu ₃ Al ₅ O ₁₂ : Pr) as a base material.

  The second light wavelength conversion layer 3 is made of a translucent resin in which phosphors are uniformly dispersed. Furthermore, the first light wavelength conversion layer 4 is made of translucent porous glass in which phosphors are uniformly dispersed.

  In addition, the above-described phosphor includes a coumarin compound, an oxazole compound, a phenyl compound, an oxadiazole compound, a rhodamine compound, a sulfodamine compound, a dicyanomethyl compound (DCM), a styryl compound, and It consists of at least one organic compound selected from pyromethane compounds.

  In the configuration as described above, in the radiation detector 1 of the present embodiment, when the radiation 8 enters the scintillator crystal 2 from the radiation source 7, scintillation light 6 corresponding to the intensity is generated. The scintillation light 6 is converted into an electrical signal by the photodetector 5, whereby the incidence of the radiation 8 is detected.

  However, the scintillator crystal 2 has a refractive index of 1.8 or more and a peak wavelength of the scintillation light 6 of 400 nm or less, and a gap between the scintillator crystal 2 and the photodetector 5 has a refractive index of 1.62 or more. The light wavelength conversion layer 4 is filled. Further, the gap between the scintillator crystal 2 and the reflecting member 9 is filled with the second light wavelength conversion layer 3 having a refractive index of less than 1.62.

  For this reason, a part of the scintillation light 6 generated in the scintillator crystal 2 first reaches the second light wavelength conversion layer 3 and the wavelength is converted. Thereby, the wavelength of the scintillation light 6 can be adapted to the wavelength sensitivity of the photodetector 5.

  At the same time, it is possible to convert the scintillation light 6 into a wavelength having a high transmittance through the scintillator crystal 2. Furthermore, it can convert into the wavelength with the high reflectance in the 2nd light wavelength conversion layer 3. FIG.

  Accordingly, the scintillation light 6 generated in the scintillator crystal 2 and reaching the second light wavelength conversion layer 3 has a wavelength suitable for the wavelength sensitivity of the photodetector 5, and as shown in FIG. The light passes through the scintillator crystal 2 while being well reflected.

  Therefore, the scintillation light 6 as described above finally reaches the first light wavelength conversion layer 4, but the reflectance at the first light wavelength conversion layer 4 is low and the transmittance is high. A part of the scintillation light 6 that has directly reached the first light wavelength conversion layer 4 by the scintillator crystal 2 also has a low reflectance and a high transmittance at the first light wavelength conversion layer 4.

  Then, when transmitting through the first light wavelength conversion layer 4, it can be converted into a wavelength suitable for the wavelength sensitivity of the photodetector 5. Accordingly, all of the scintillation light 6 finally enters the photodetector 5 with good efficiency.

  For this reason, in the radiation detector 1 of this Embodiment, it becomes possible to increase the electrical signal output from the photodetector 5 significantly, and can increase the detection sensitivity of the radiation detector 1 as a result. It becomes possible.

Here, the operation of the radiation detector 1 as described above will be verified. First, when the reflection angle of the light emitted from the scintillator crystal at the interface with the optical wavelength conversion layer is θ ₁ , the refractive angle is θ ₂ , the refractive index of the scintillator crystal is n 1, and the refractive index of the optical wavelength conversion layer is n 2,
n1 · sin θ ₁ = n2 · sin θ ₂
It becomes.

Further, when the angle (θ ₂ = 90 °) at the time of total reflection of light in the scintillator crystal having the refractive index n1, that is, the critical angle τ is obtained,
τ = sin ⁻¹ (n2 / n1)
It becomes.

The reflectance R at the interface between the scintillator crystal and the light wavelength conversion layer is
R = (n1-n2) ² / (n1 + n2) ²
It becomes.

  Therefore, the greater the difference in refractive index between the scintillator crystal and the light wavelength conversion layer, the greater the critical angle τ and the greater the reflectance R. That is, the greater the difference in refractive index between the scintillator crystal and the light wavelength conversion layer, the greater the proportion of light that is totally reflected at the interface between the scintillator crystal and the light wavelength conversion layer.

  In the conventional radiation detector, the scintillation light emitted from the scintillator crystal is directly supplied to a photodetector such as PMT or PD, and is converted into an electric signal proportional to the intensity of the scintillation light in this photodetector. .

However, in a scintillator crystal whose emission peak wavelength is 400 nm or less, such as CsI or praseodymium-added lutetium aluminate (Lu ₃ Al ₅ O ₁₂ : Pr), a wavelength suitable for the wavelength sensitivity (quantum conversion efficiency) such as PMT and PD However, there is a problem that the light conversion efficiency is low.

In addition, in the scintillator crystals such as CsI, praseodymium-added lutetium aluminate (Lu ₃ Al ₅ O ₁₂ : Pr), and CeF ₃ , the transmittance at the peak wavelength of light emission of the scintillator crystal is increased in the longer wavelength region. Small compared.

  For this reason, there is a problem that the intensity of the scintillation light is attenuated due to self-absorption until the scintillation light reaches the photodetector, and the light conversion efficiency and detection sensitivity of the radiation detector 1 are lowered.

  For example, as shown in FIG. 2, the light wavelength conversion layer 0 is formed around the scintillator crystal 2, one of the surfaces is bonded to the photodetector 5, and the remaining surface is covered with the reflecting member 9. In the case where the light wavelength conversion layer 0 having a large refractive index difference from the scintillator crystal 2 is formed between the scintillator crystal 2 and the reflecting member 9, light emitted from the scintillator crystal 2 is transmitted through the light wavelength conversion layer 0. The ratio is reduced.

  For this reason, when the light transmitted through the light wavelength conversion layer 0 reaches the reflection member 9, scattering at the interface between the reflection member 9 and the light wavelength conversion layer 0 and the influence of the light component transmitted through the reflection member 9, The problem of light attenuation can be reduced. As a result, the amount of light reaching the photodetector 5 increases.

  Further, when the light wavelength conversion layer 0 having a small refractive index difference from the scintillator crystal 2 is formed between the scintillator crystal 2 and the photodetector 5, the light emitted from the scintillator crystal 2 is totally reflected by the light wavelength conversion layer 0. Since the ratio decreases, the amount of light reaching the photodetector 5 increases.

  In addition, the graph of the wavelength sensitivity (quantum conversion efficiency) of PMT and PD which are generally used photodetectors in the radiation detector 1 as described above is illustrated in FIG. In order to convert the scintillation light 6 into an electric signal with high conversion efficiency, it is preferable that the scintillation light 6 has an emission peak wavelength in a wavelength region near 400 to 600 nm.

FIG. 4 is a graph showing an emission spectrum and a transmission spectrum of praseodymium-added lutetium aluminate (Lu ₃ Al ₅ O ₁₂ : Pr). The emission peak wavelength is 310 nm, which is not a wavelength suitable for wavelength sensitivity (quantum conversion efficiency) such as PMT and PD.

FIG. 5 is a graph showing an emission spectrum and an absorption spectrum of CeF ₃ . The emission peak wavelength is 300 nm, which is not a wavelength suitable for the wavelength sensitivity (quantum conversion efficiency) such as PMT and PD.

  Therefore, as shown in FIG. 1, the radiation detector 1 of the present embodiment includes a scintillator crystal 2 having a refractive index n1 (n1 is a specific real number) or more that generates scintillation light 6 inside by the incidence of radiation 8. The gap between the scintillator crystal 2 and the reflection member 9 is filled in the gap between the scintillator crystal 2 and the photodetector 5 and the refractive index is n2 (n2 is a real number less than n1) or more, and the gap between the scintillator crystal 2 and the reflecting member 9. And a scintillator crystal 2 having a peak wavelength of the scintillation light 6 of 400 nm or less and a refractive index of 1.8 or more, a scintillator crystal 2 and a photodetector. 5 is filled in the gap between the first light wavelength conversion layer 4 having a refractive index of 1.62 or more and the scintillator crystal 2 and the reflecting member 9 and having a refractive index of less than 1.62. Dual light wavelength It has a 換層 3, a.

  For this reason, the wavelength of the scintillation light 6 can be adapted to the wavelength sensitivity of the photodetector 5 by the second light wavelength conversion layer 3, and the scintillator crystal 2 can be effectively converted to a wavelength with high transmittance. it can.

  In addition, since the refractive index difference between the scintillator crystal 2 and the second light wavelength conversion layer 3 is sufficiently large, the scintillation light 6 is efficiently reflected before reaching the first light wavelength conversion layer 4 efficiently.

  Since the difference in refractive index between the scintillator crystal 2 and the first light wavelength conversion layer 4 is sufficiently small, the scintillation light 6 efficiently reaches the photodetector 5 without being reflected by the first light wavelength conversion layer 4.

  Therefore, the photoelectric conversion efficiency in the photodetector 5 is greatly increased, the number of photons reaching the photodetector 5 is increased, and the radiation detector 1 has high sensitivity and excellent energy resolution.

Lu ₃ Al ₅ O ₁₂ : Pr investigated by the present inventors as a constituent material of the scintillator crystal 2 has no deliquescent property, and has the shortest fluorescence lifetime (less than 22 nsec) of LSO and the highest among oxide scintillator crystals. It is a scintillator crystal 2 having an excellent characteristic of energy resolution (˜5%).

Further, it is a scintillator crystal 2 that does not have CeF ₃ deliquescence and has characteristics such as a shorter fluorescence lifetime than LSO (30 nsec or less) and the highest energy resolution (˜18%) among fluoride scintillator crystals.

FIG. 6 is a graph showing an emission spectrum of the scintillator crystal 2 made of Lu ₃ Al ₅ O ₁₂ : Pr when each of the light wavelength conversion layers 3 and 4 containing diphenyloxazole or the like as a phosphor is formed.

FIG. 7 is a graph showing an emission spectrum of the scintillator crystal 2 made of CeF ₃ when the respective light wavelength conversion layers 3 and 4 containing diphenyloxazole or the like as a phosphor are formed.

  As shown in FIGS. 6 and 7, the peak wavelength of the emission spectrum of the scintillator crystal 2 having the light wavelength conversion layers 3 and 4 is around 420 nm, and this value is the PMT as the photodetector 5 as shown in FIG. And close to the peak response wavelength of PD.

Moreover, _Lu 3 _Al 5 _O 12, as shown in FIGS. 3 and 4: the wavelength high transmittance of Pr and CeF ₃ with the peak wavelength of the emission spectrum. Therefore, by forming the respective light wavelength conversion layers 3 and 4 as described above, the scintillator crystal 2 that can be converted into light having a wavelength suitable for the photodetector 5 is obtained, and at the same time, the photoelectric in the photodetector 5 is obtained. The conversion efficiency is greatly increased, the number of photons reaching the photodetector 5 is increased, and the radiation detector 1 has high sensitivity and excellent energy resolution.

  In addition, the light wavelength conversion layers 3 and 4 can be composed of not only a single layer but also a plurality of layers containing fluorescent materials having different characteristics. For example, by converting the scintillation light 6 having a wavelength of about 200 mm into blue-green light having a longer wavelength of about 300 to 350 nm, and further converting this converted light into longer wavelength scintillation light 6 It is also possible to further increase the photoelectric conversion efficiency in the PMT and PD.

  Further, in the radiation detector 1 as described above, the photodetector 5 may be composed of a semiconductor light receiving element formed of a set of normal mode APD or Geiger mode APD pixels (not shown).

Next, as a further specific example of the radiation detector according to the present invention, a plurality of embodiments will be described below with reference to FIGS. First, Lu ₃ Al ₅ O ₁₂ : Pr (refractive index: 1.8) and CeF ₃ (refractive index: 1.68) were cut into 1 × 1 × 1 cm cubes, and the six surfaces were mirror-polished. .

  In addition, a solution in which a polysiloxane-based silicone resin as a translucent resin material is dissolved in toluene and a saturated solution in which diphenyloxazole and 1,4 bis (5-phenyl-2-oxazolyl) benzene are mixed are prepared, and refraction is performed. A resin slurry serving as a base of the second light wavelength conversion layer having a rate of less than 1.62 was prepared.

  Further, tetramethoxysilane as a translucent resin material was dissolved in a mixed solvent of methanol and water, and n, n-dimethylformamide was added as a drying control agent to gel and ripen to obtain a wet gel.

A wet gel was applied to one surface of the cubic Lu ₃ Al ₅ O ₁₂ : Pr and then dried to obtain a porous glass having a thickness of 100 μm. The obtained porous glass was immersed in a saturated toluene solution in which diphenyloxazole and 1,4bis (5-phenyl2-oxazolyl) benzene were mixed, fluorescent molecules were introduced into the pores, and the refractive index was 1.62. The above first light wavelength conversion layer was formed.

[Example 1]
The resin slurry is applied to the other five surfaces of the cubic Lu ₃ Al ₅ O ₁₂ : Pr on which the first light wavelength conversion layer having the above refractive index of 1.62 or more is formed on one surface, and is dried and cured, thereby obtaining 100 μm. A scintillator crystal was made of cubic Lu ₃ Al ₅ O ₁₂ : Pr in which a second light wavelength conversion layer having a refractive index of less than 1.62 and having a refractive index of less than 1.62 was integrally formed.

  Next, the five surfaces on which the second light wavelength conversion layer having a refractive index of less than 1.62 is formed are covered with a reflecting member, and the one surface on which the first light wavelength conversion layer having a refractive index of 1.62 or more is formed is defined as PMT (R9800). ) Was optically bonded to the incident surface to form a radiation detector.

[Example 2]
The other five surfaces of the cubic Lu ₃ Al ₅ O ₁₂ : Pr on which the first optical wavelength conversion layer having the refractive index of 1.62 or more is formed on one surface are covered with a reflecting member, and the first refractive index is 1.62 or more. One surface on which the one-light wavelength conversion layer was formed was optically bonded to the incident surface of the PMT (R9800) to constitute a radiation detector.

[Example 3]
The resin slurry is applied to the entire surface of the cubic Lu ₃ Al ₅ O ₁₂ : Pr and dried and cured to form a second light wavelength conversion layer having a refractive index of less than 1.62 having a thickness of 100 μm. A scintillator crystal was made of cubic Lu ₃ Al ₅ O ₁₂ : Pr by covering the five sides with a reflecting member. Next, the remaining surface was optically bonded to the incident surface of the PMT (R9800) to constitute a radiation detector.

[Example 4]
The resin slurry is applied to five surfaces of cubic Lu ₃ Al ₅ O ₁₂ : Pr and dried and cured to form a second light wavelength conversion layer having a refractive index of less than 1.62 having a thickness of 100 μm. The surface was covered with a reflective member, and a scintillator crystal was made of cubic Lu ₃ Al ₅ O ₁₂ : Pr. Next, one surface not covered with the reflecting member was optically bonded to the incident surface of the PMT (R9800) to constitute a radiation detector.

[Example 5]
The resin slurry was applied to two opposite surfaces of the cubic Lu ₃ Al ₅ O ₁₂ : Pr and dried and cured to form a second light wavelength conversion layer having a refractive index of less than 1.62 having a thickness of 100 μm.

A scintillator crystal was made of cubic Lu ₃ Al ₅ O ₁₂ : Pr by covering one surface of these and four surfaces on which each light wavelength conversion layer was not formed with a reflecting member. Next, one surface not covered with the reflecting member was optically bonded to the incident surface of the PMT (R9800) to constitute a radiation detector.

[Comparative Example 1]
The resin slurry is applied to one surface of the cubic Lu ₃ Al ₅ O ₁₂ : Pr and dried and cured to form a second light wavelength conversion layer having a refractive index of less than 1.62 having a thickness of 100 μm. And the four surfaces where each light wavelength conversion layer in contact with this one surface was not formed were covered with a reflecting member, and a scintillator crystal was made of cubic Lu ₃ Al ₅ O ₁₂ : Pr.

  Next, one surface not covered with the reflecting member was optically bonded to the incident surface of the PMT (R9800) to constitute a radiation detector. In addition, the various characteristics of above-mentioned Examples 1-5 and the comparative example 1 are shown in FIG.

[Example 6]
The resin slurry is applied to the other five surfaces of the cubic CeF ₃ on which the first light wavelength conversion layer having the refractive index of 1.62 or more is formed on one surface, and then dried and cured to obtain a refractive index having a thickness of 100 μm. A scintillator crystal was made of cubic CeF ₃ integrally formed with a second light wavelength conversion layer of less than 1.62.

  Next, the five surfaces on which the second light wavelength conversion layer having a refractive index of less than 1.62 is formed are covered with a reflecting member, and the one surface on which the first light wavelength conversion layer having a refractive index of 1.62 or more is formed is defined as PMT (R9800). ) Was optically bonded to the incident surface to form a radiation detector.

[Example 7]
The other five surfaces of the cubic CeF ₃ on which the first light wavelength conversion layer having a refractive index of 1.62 or more is formed on one surface are covered with a reflecting member, and the first light wavelength conversion layer having a refractive index of 1.62 or more is covered. The formed surface was optically bonded to the incident surface of PMT (R9800) to constitute a radiation detector.

[Example 8]
The resin slurry is applied to the entire surface of the cubic CeF ₃ and dried and cured to form a second light wavelength conversion layer having a refractive index of less than 1.62 having a thickness of 100 μm, and five of these layers are made of a reflecting member. A scintillator crystal was made of CeF ₃ in a cover cube. Next, the remaining surface was optically bonded to the incident surface of the PMT (R9800) to constitute a radiation detector.

[Example 9]
The resin slurry is applied to five sides of the cubic CeF ₃ and dried and cured to form a second light wavelength conversion layer having a refractive index of less than 1.62 having a thickness of 100 μm, and the five sides are covered with a reflecting member. A scintillator crystal was made of cubic CeF ₃ . Next, one surface not covered with the reflecting member was optically bonded to the incident surface of the PMT (R9800) to constitute a radiation detector.

[Example 10]
The resin slurry is applied to two opposite surfaces of the cubic CeF ₃ and dried and cured to form a second light wavelength conversion layer having a refractive index of less than 1.62 having a thickness of 100 μm. The four surfaces on which the respective light wavelength conversion layers were not formed were covered with a reflecting member, and a scintillator crystal was made of cubic CeF ₃ . Next, one surface not covered with the reflecting member was optically bonded to the incident surface of the PMT (R9800) to constitute a radiation detector.

[Comparative Example 2]
The resin slurry is applied to one surface of the cubic CeF ₃ and dried and cured to form a second light wavelength conversion layer having a refractive index of less than 1.62 having a thickness of 100 μm, and this one surface and this one surface are in contact with each other. The four surfaces on which each light wavelength conversion layer was not formed were covered with a reflecting member, and a scintillator crystal was made of cubic CeF ₃ .

  Next, one surface not covered with the reflecting member was optically bonded to the incident surface of the PMT (R9800) to constitute a radiation detector. In addition, the various characteristics of above-mentioned Examples 6-10 and the comparative example 2 are shown in FIG.

FIG. 9 shows the amount of light emitted when the radiation detectors of Examples 6 to 10 and the radiation detector using standard CeF3 when each light wavelength conversion layer is not formed are irradiated with ¹³⁷ Csγ rays. . In the radiation detectors of Examples 6 to 10, the amount of luminescence increased compared to the standard radiation detector.

  In particular, the five surfaces on which the second light wavelength conversion layer having a refractive index of less than 1.62 is formed are covered with a reflecting member, and the one surface on which the first light wavelength conversion layer having a refractive index of 1.62 or more is formed is PMT (R9800). In the case of Example 6 optically bonded to the incident surface, the light emission amount was maximized.

[Example 11]
The resin slurry is applied to the other five surfaces of the cube Lu ₃ A1 ₅ 0 ₁₂ : Pr on which the first light wavelength conversion layer having the refractive index of 1.62 or more is formed on one surface, and is dried and cured, thereby obtaining 100 μm. A scintillator crystal was made of cubic Lu ₃ A1 ₅ 0 ₁₂ : Pr in which a second light wavelength conversion layer having a refractive index of less than 1.62 and a refractive index of less than 1.62 was also integrally formed.

  Next, the five surfaces on which the second light wavelength conversion layer having a refractive index of less than 1.62 is formed are covered with a reflecting member, and the one surface on which the first light wavelength conversion layer having a refractive index of 1.62 or more is formed is converted into a normal mode. A radiation detector was configured by optically bonding to an incident surface of a semiconductor light receiving element made of APD (S8664-8221 manufactured by Hamamatsu Photonics).

[Example 12]
The other five surfaces of the cube Lu ₃ A1 ₅ 0 ₁₂ : Pr on which the first light wavelength conversion layer having a refractive index of 1.62 or more is formed on one surface are covered with a reflecting member, and the first refractive index is 1.62 or more. One surface on which the one-light wavelength conversion layer was formed was optically bonded to the incident surface of a semiconductor light-receiving element made of normal mode APD (S8664-8221 manufactured by Hamamatsu Photonics) to constitute a radiation detector.

[Example 13]
Cubic Lu ₃ A1 ₅ 0 ₁₂ : The resin slurry is applied to the entire surface of Pr and dried and cured to form a second light wavelength conversion layer having a refractive index of less than 1.62 having a thickness of 100 μm. A scintillator crystal was made of cubic Lu ₃ A1 ₅ 0 ₁₂ : Pr by covering the five faces with a reflecting member. Next, the remaining one surface was optically bonded to the incident surface of a semiconductor light receiving element composed of a normal mode APD (S8664-8221 manufactured by Hamamatsu Photonics) to constitute a radiation detector.

[Example 14]
The resin slurry is applied to the five surfaces of the cube Lu ₃ A1 ₅ 0 ₁₂ : Pr and dried and cured to form a second light wavelength conversion layer having a refractive index of less than 1.62 having a thickness of 100 μm. The surface was covered with a reflecting member, and a scintillator crystal was made of cubic Lu ₃ A1 ₅ 0 ₁₂ : Pr. Next, the one surface not covered with the reflecting member was optically bonded to the incident surface of the semiconductor light receiving element composed of the normal mode APD (S8664-8221 manufactured by Hamamatsu Photonics) to constitute a radiation detector.

[Example 15]
The resin slurry was applied to two opposing surfaces of the cube Lu ₃ A1 ₅ 0 ₁₂ : Pr and dried and cured to form a second light wavelength conversion layer having a refractive index of less than 1.62 having a thickness of 100 μm.

A scintillator crystal was made of cubic Lu ₃ A1 ₅ 0 ₁₂ : Pr by covering one surface of these and four surfaces on which each light wavelength conversion layer was not formed with a reflecting member. Next, the one surface not covered with the reflecting member was optically bonded to the incident surface of the semiconductor light receiving element composed of the normal mode APD (S8664-8221 manufactured by Hamamatsu Photonics) to constitute a radiation detector.

[Comparative Example 3]
Cubic Lu ₃ A1 ₅ 0 ₁₂ : The resin slurry is applied to one surface of Pr and dried and cured to form a second light wavelength conversion layer having a refractive index of less than 1.62 having a thickness of 100 μm. Further, the four surfaces on which the respective light wavelength conversion layers in contact with the one surface were not formed were covered with a reflecting member, and a scintillator crystal was produced with cubic Lu ₃ A1 ₅ 0 ₁₂ : Pr.

  Next, the one surface not covered with the reflecting member was optically bonded to the entrance surface of the semiconductor light receiving element composed of normal mode APD (S8664-8221 manufactured by Hamamatsu Photonics) to constitute a radiation detector. In addition, the various characteristics of the above-mentioned Examples 11-15 and the comparative example 3 are shown in FIG.

  FIG. 10 shows the light emission amounts of the radiation detectors of Examples 11 to 15 and the standard radiation detector when each light wavelength conversion layer is not formed. In the radiation detectors of Examples 11 to 15, the amount of light emission increased dramatically compared to the standard radiation detector.

In particular, the five surfaces on which the second light wavelength conversion layer having a refractive index of less than 1.62 is formed are covered with a reflecting member, and the one surface on which the first light wavelength conversion layer having a refractive index of 1.62 or more is formed is made of APD. In the case of Example 11 optically bonded to the incident surface of the semiconductor light receiving element, the light emission amount was maximized.
[Example 16]
The resin slurry is applied to the other five surfaces of the cube Lu ₃ A1 ₅ 0 ₁₂ : Pr on which the first light wavelength conversion layer having the refractive index of 1.62 or more is formed on one surface, and is dried and cured, thereby obtaining 100 μm. A scintillator crystal was made of cubic Lu ₃ A1 ₅ 0 ₁₂ : Pr integrally formed with a second light wavelength conversion layer having a refractive index of less than 1.62 and a refractive index of less than 1.62.

  Next, the five surfaces on which the second light wavelength conversion layer having a refractive index of less than 1.62 is formed are covered with a reflecting member, and the one surface on which the first light wavelength conversion layer having a refractive index of 1.62 or more is formed is converted into a Geiger mode. A radiation detector was configured by optically bonding to an incident surface of a semiconductor light receiving element made of MPPC (registered trademark) (10362-33-050 manufactured by Hamamatsu Photonics), which is a set of APDs.

[Example 17]
The other five surfaces of the cube Lu ₃ A1 ₅ 0 ₁₂ : Pr on which the first light wavelength conversion layer having a refractive index of 1.62 or more is formed on one surface are covered with a reflecting member, and the first refractive index is 1.62 or more. One surface on which the one-light wavelength conversion layer is formed is optically bonded to an incident surface of a semiconductor light receiving element made of MPPC (manufactured by Hamamatsu Photonics, 10362-33-050), which is a set of Geiger mode APDs, to constitute a radiation detector. .

[Example 18]
Cubic Lu ₃ A1 ₅ 0 ₁₂ : The resin slurry is applied to the entire surface of Pr and dried and cured to form a second light wavelength conversion layer having a refractive index of less than 1.62 having a thickness of 100 μm. A scintillator crystal was made of cubic Lu ₃ A1 ₅ 0 ₁₂ : Pr by covering the five faces with a reflecting member.

  Next, the remaining surface was optically bonded to the incident surface of a semiconductor light receiving element made of MPPC (10362-33-050 manufactured by Hamamatsu Photonics), which is a set of Geiger mode APDs, to constitute a radiation detector.

[Example 19]
The resin slurry is applied to the five surfaces of the cube Lu ₃ A1 ₅ 0 ₁₂ : Pr and dried and cured to form a second light wavelength conversion layer having a refractive index of less than 1.62 having a thickness of 100 μm. The surface was covered with a reflecting member, and a scintillator crystal was made of cubic Lu ₃ A1 ₅ 0 ₁₂ : Pr.

  Next, one surface not covered with the reflecting member is optically bonded to the incident surface of the semiconductor light receiving element made of MPPC (manufactured by Hamamatsu Photonics, 10362-33-050), which is a set of Geiger mode APDs, and the radiation detector is attached. Configured.

[Example 20]
The resin slurry was applied to two opposing surfaces of the cube Lu ₃ A1 ₅ 0 ₁₂ : Pr and dried and cured to form a second light wavelength conversion layer having a refractive index of less than 1.62 having a thickness of 100 μm.

A scintillator crystal was made of cubic Lu ₃ A1 ₅ 0 ₁₂ : Pr by covering one surface of these and four surfaces on which each light wavelength conversion layer was not formed with a reflecting member. Next, one surface not covered with the reflecting member is optically bonded to the incident surface of the semiconductor light receiving element made of MPPC (manufactured by Hamamatsu Photonics, 10362-33-050), which is a set of Geiger mode APDs, and the radiation detector is attached. Configured.

[Comparative Example 4]
Cubic Lu ₃ A1 ₅ 0 ₁₂ : The resin slurry is applied to one surface of Pr and dried and cured to form a second light wavelength conversion layer having a refractive index of less than 1.62 having a thickness of 100 μm. Further, the four surfaces on which the respective light wavelength conversion layers in contact with the one surface were not formed were covered with a reflecting member, and a scintillator crystal was produced with cubic Lu ₃ A1 ₅ 0 ₁₂ : Pr.

  Next, one surface not covered with the reflecting member is optically bonded to the entrance surface of the semiconductor light receiving element made of MPPC (manufactured by Hamamatsu Photonics, 10362-33-050), which is a set of Geiger mode APDs, and a radiation detector is attached. Configured. In addition, the various characteristics of above-mentioned Examples 16-20 and the comparative example 4 are shown in FIG.

  FIG. 11 shows the light emission amounts of the radiation detectors of Examples 16 to 20 and the standard radiation detector when each light wavelength conversion layer is not formed. In the radiation detectors of Examples 16 to 20, the amount of luminescence increased dramatically compared to the standard radiation detector.

  In particular, the five surfaces on which the second light wavelength conversion layer having a refractive index of less than 1.62 is formed are covered with a reflecting member, and the one surface on which the first light wavelength conversion layer having a refractive index of 1.62 or more is formed is incident on the MPPC. In the case of Example 16 optically bonded to the substrate, the light emission amount was maximized.

DESCRIPTION OF SYMBOLS 1 Radiation detector 2 Scintillator crystal 3 2nd light wavelength conversion layer 4 1st light wavelength conversion layer 5 Photodetector 6 Scintillation light 7 Radiation source 8 Radiation 9 Reflective member

Claims (7)

A radiation detector for detecting the incidence of radiation,
A scintillator crystal having a refractive index n1 (n1 is a specific real number) or more that generates scintillation light inside by the incidence of the radiation;
A photodetector that is disposed at a position facing the scintillator crystal and converts the incident scintillation light into an electrical signal;
A first light wavelength conversion layer filled in a gap between the scintillator crystal and the photodetector and having a refractive index of n2 (n2 is a real number less than n1) or more;
A reflecting member that is disposed at a position facing a surface other than one surface of the scintillator crystal facing the photodetector and reflects the incident scintillation light;
A second light wavelength conversion layer filled in a gap between the scintillator crystal and the reflecting member and having a refractive index of less than the n2,
A radiation detector. The scintillator crystal has a peak wavelength of the scintillation light of 400 nm or less and a refractive index n1 of 1.8 or more.
The first light wavelength conversion layer has the refractive index n2 of 1.62 or more,
The radiation detector according to claim 1, wherein the second light wavelength conversion layer has the refractive index n2 of less than 1.62.   The radiation detector according to claim 2, wherein the second light wavelength conversion layer is made of a translucent resin in which phosphors are uniformly dispersed.   The radiation detector according to any one of claims 1 to 3, wherein the first light wavelength conversion layer is made of translucent porous glass in which phosphors are uniformly dispersed.   The phosphor includes a coumarin compound, an oxazole compound, a phenyl compound, an oxadiazole compound, a rhodamine compound, a sulfododamine compound, a dicyanomethyl compound (DCM), a styryl compound, and a pyromethane compound. The radiation detector according to claim 3, comprising at least one organic compound selected from the group consisting of:   The radiation detector according to any one of claims 1 to 5, wherein the scintillator crystal is composed of praseodymium-added lutetium aluminate.   The radiation detector according to any one of claims 1 to 6, wherein the photodetector is a semiconductor light receiving element including a set of normal mode APD or Geiger mode APD pixels.

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