JP5769934B2 - Radiation detector - Google Patents
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- JP5769934B2 JP5769934B2 JP2010148331A JP2010148331A JP5769934B2 JP 5769934 B2 JP5769934 B2 JP 5769934B2 JP 2010148331 A JP2010148331 A JP 2010148331A JP 2010148331 A JP2010148331 A JP 2010148331A JP 5769934 B2 JP5769934 B2 JP 5769934B2
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Description
本発明は、シンチレータを用いた放射線検出器に関するものである。 The present invention relates to a radiation detector using a scintillator.
従来のこの種の放射線検出器では、シンチレータの所定面を蛍光取出面としてこの蛍光取出面に光検出器を接続するとともに、他の面には光反射材を塗布又は貼り付けてシンチレータ内で発生した蛍光を逃がすことなく蛍光取出面から効率よく取り出せるようにしている。 In this type of conventional radiation detector, a predetermined surface of the scintillator is used as a fluorescence extraction surface, a photodetector is connected to this fluorescence extraction surface, and light reflection material is applied or pasted on the other surface to generate in the scintillator. The fluorescent light can be efficiently extracted from the fluorescent light extraction surface without escaping.
また、例えば特許文献１には、光反射材を前記他の面から離間させてそれらの間に空気層を設けるとともに、当該他の面の表面粗さを蛍光波長よりも大きい値に設定した放射線検出器が記載されている。 Further, for example, in Patent Document 1, the light reflecting material is separated from the other surface, an air layer is provided between them, and the surface roughness of the other surface is set to a value larger than the fluorescence wavelength. A detector is described.
表面粗さとは１つの値で定まるものではなく各種の値を有するものであり、特許文献１で述べられている表面粗さがそのどれに該当するのかは不明ではあるものの、上述した構成によって、この特許文献１以前の放射線検出器とは異なり、前記他の面の表面粗さの値に依存することなく空気層に漏れる蛍光の比率が一定となり、機器間の出力特性のばらつきを抑制できるとしてある。 The surface roughness is not determined by one value but has various values, and it is not clear which surface roughness described in Patent Document 1 corresponds to, but by the configuration described above, Unlike the radiation detectors before this patent document 1, the ratio of fluorescence leaking into the air layer is constant without depending on the value of the surface roughness of the other surface, and variation in output characteristics between devices can be suppressed. is there.
また、この特許文献１では、蛍光取出面の表面粗さを前記他の面の表面粗さと同一又はそれよりも小さくすることによって、蛍光の光検出器への伝達率が向上し、放射線検出感度の向上を図れるとも記載している。 Moreover, in this patent document 1, by making the surface roughness of the fluorescence extraction surface the same or smaller than the surface roughness of the other surface, the transmission rate of fluorescence to the photodetector is improved, and the radiation detection sensitivity is increased. It also states that it can improve.
しかしながら、本願発明者が鋭意検討した結果、前記他の面の表面粗さを特許文献１のように粗くすると、シンチレータと空気層との間での蛍光の全反射量が減り、多くの蛍光は空気層に漏れてその後ろにある反射面で反射し、再度シンチレータに導入されることとなる。そして、前記境界での全反射においては反射率が１００％であるのに対し、前記反射面での反射では、吸収が生じてそれに遠く及ばないことから、実際には蛍光取出効率が悪くなる。 However, as a result of intensive studies by the inventor of the present application, if the surface roughness of the other surface is roughened as in Patent Document 1, the total amount of fluorescence reflected between the scintillator and the air layer is reduced, and much fluorescence is generated. It leaks into the air layer, reflects off the reflective surface behind it, and is again introduced into the scintillator. The total reflection at the boundary has a reflectance of 100%, whereas the reflection at the reflection surface absorbs and does not reach the distance, so that the fluorescence extraction efficiency actually deteriorates.
また、本発明者によるこれまでの実験やシミュレーションによれば、蛍光取出面の表面粗さを大きく設定しても、鏡面のように表面粗さを小さく設定したものと光伝達効率は大差なく、逆に蛍光取出面の表面粗さが大きい方が光伝達効率がよい場合もある（詳細は後述する）。さらに、薄板状シンチレータの場合、蛍光取出面はシンチレータの側端面に設定される場合が多く、特許文献１のようにその薄い幅の側端面の表面粗さを蛍光の波長以下にまで仕上げるには多大な手間がかかる。そうすると、光伝達効率向上という微妙で不確定なメリットよりも、むしろ、その加工手間によるコストアップ等のデメリットが大きな問題となる。
本発明は、かかる課題を鑑みてなされたものであって、蛍光取出効率を向上できるとともに、簡単に製造できる放射線検出器を提供すべく図ったものである。
In addition, according to the experiments and simulations so far by the present inventor, even if the surface roughness of the fluorescence extraction surface is set large, the light transmission efficiency is not much different from that set to a small surface roughness like a mirror surface, Conversely, the light transmission efficiency may be better when the surface roughness of the fluorescence extraction surface is larger (details will be described later). Furthermore, in the case of a thin plate scintillator, the fluorescence extraction surface is often set to the side end surface of the scintillator, and as in Patent Document 1, the surface roughness of the thin side end surface is made to be less than the fluorescence wavelength. It takes a lot of work. Then, rather than the subtle and uncertain merits of improving the light transmission efficiency, the demerits such as the cost increase due to the processing effort become a big problem.
The present invention has been made in view of such problems, and is intended to provide a radiation detector that can improve fluorescence extraction efficiency and can be easily manufactured.
すなわち、本発明に係る放射線検出器は、表面のうちの１以上の面を蛍光取出面として設定するとともに、その他の面を鏡面とし、前記蛍光取出面を、前記その他の面よりも面粗さが粗い粗面としたシンチレータと、前記蛍光取出面に臨ませて配置した受光機構と、前記その他の面に対向させつつ一定距離離間させて配置した反射部材とを具備していることを特徴とする。 That is, in the radiation detector according to the present invention, one or more of the surfaces are set as the fluorescence extraction surface, the other surface is a mirror surface, and the fluorescence extraction surface is more rough than the other surfaces. A scintillator having a rough surface, a light receiving mechanism disposed facing the fluorescence extraction surface, and a reflecting member disposed at a predetermined distance while facing the other surface. To do.
なお、鏡面とは、蛍光を実質的に散乱させることなく略正反射する表面粗さを有した面のことであり、粗面とは、蛍光が実質的に散乱する粗さを有した面のことである。より具体的には、例えば鏡面の表面粗さとして、ＪＩＳ規格で言う算術平均高さＲａ及び／又は最大高さＲｚ及び／又は十点平均高さＲｚＪＩＳが、蛍光の波長よりも小さいものを挙げることができ、粗面は前記鏡面よりも粗い表面を挙げることができる。 The mirror surface is a surface having a surface roughness that substantially reflects specularly without substantially scattering fluorescence, and the rough surface is a surface having a roughness that substantially scatters fluorescence. That is. More specifically, for example, as the surface roughness of the mirror surface, the arithmetic average height Ra and / or the maximum height Rz and / or the ten-point average height Rz in the JIS standard is smaller than the fluorescence wavelength. The rough surface may be a surface rougher than the mirror surface.
しかしてこのようなものであれば、放射線照射によって生じたシンチレータ内での蛍光のうち、前記その他の面に対して一定以上浅い角度で進むものは、前記その他の面が空隙層に露出した鏡面であることから、空隙層との屈折率の違いによってここで１００％の効率で全反射される一方、それよりも深い角度で進入したものは、前記その他の面を抜けてその外側にある反射部材によって反射される。 If this is the case, among the fluorescence in the scintillator produced by radiation irradiation, the one that advances at a shallow angle with respect to the other surface is a mirror surface in which the other surface is exposed to the void layer. Therefore, the light is totally reflected at an efficiency of 100% due to the difference in refractive index from the gap layer, while the light entering at a deeper angle passes through the other surface and is reflected outside. Reflected by the member.
すなわち、反射部材とその他の面との間に空隙層を設け、かつ該その他の面を鏡面としておくことによって、所定割合の蛍光が、確実に当該その他の面で全反射されることととなり、空隙層に漏れた残りの蛍光だけが反射部材で反射されることとなる。その結果、例えばシンチレータの表面に反射部材を塗布したもののように、全ての蛍光を反射部材で反射するものよりも反射効率が１００％の全反射を有効使用できる分、全体としての反射効率が格段に向上するし、特許文献１のように、全反射の割合が小さいものに比べても、やはり反射効率が大きく向上する。このようにして、本発明によれば、蛍光を最大効率で蛍光取出面から導出することができるようになる。 That is, by providing a gap layer between the reflecting member and the other surface, and by setting the other surface as a mirror surface, the predetermined ratio of fluorescence is surely totally reflected by the other surface, Only the remaining fluorescence leaking into the gap layer is reflected by the reflecting member. As a result, for example, the total reflection efficiency is remarkably high because the total reflection with 100% reflection efficiency can be used more effectively than the case where all the fluorescence is reflected by the reflection member, such as the case where the reflection member is applied to the surface of the scintillator. In addition, the reflection efficiency is greatly improved as compared with the case where the ratio of total reflection is small as in Patent Document 1. In this way, according to the present invention, fluorescence can be derived from the fluorescence extraction surface with maximum efficiency.
また、蛍光取出面が粗面であることは、上述した本発明者による検討からも明らかなように、光伝達を阻害する積極的な要因にはなり得ず、逆に、表面仕上げ加工の手間を削減できることによって、製造の簡単化やコストダウンに寄与し得る。 In addition, the fact that the fluorescence extraction surface is a rough surface cannot be an active factor that hinders light transmission, as is clear from the above-described study by the present inventor. Can contribute to simplification of manufacturing and cost reduction.
より具体的な実施態様としては、前記シンチレータが等厚薄板状をなすものであり、該シンチレータの表裏両面を前記その他の面とするとともに、周囲の側端面を蛍光取出面としたものを挙げることができる。このようなシンチレータであると、蛍光取出面である側端面を粗く仕上げてもよいということとなり、シンチレータの側端面に実質的にほぼ仕上げ加工を施さず、ほぼ切りっぱなしでもよいということにつながるため、加工を大幅に簡素化できてその点での本発明の効果が顕著となる。 As a more specific embodiment, the scintillator has a thin plate shape of equal thickness, and both the front and back surfaces of the scintillator are the other surfaces, and the peripheral side end surface is a fluorescence extraction surface. Can do. With such a scintillator, the side end surface, which is the fluorescence extraction surface, may be roughly finished, which means that the side end surface of the scintillator is substantially not subjected to finishing and may be left almost cut off. Therefore, the processing can be greatly simplified, and the effect of the present invention in that respect becomes remarkable.
本発明者が鋭意検討した結果によれば、前記受光機構が、等厚薄板状をなし一端を前記蛍光取出面に対向させて配置したライトガイドを備えたものにおいて、前記ライトガイドの厚み寸法をシンチレータの厚み寸法よりも若干大きく設定したものの蛍光伝達効率がよいことが判明した。具体的には、ライトガイドの厚み寸法がシンチレータの厚み寸法の１．１〜２．０倍、より厳密には約１．５倍が好ましい。 According to the results of intensive studies by the inventor, the light receiving mechanism has a light guide in which the light receiving mechanism has an equal thickness thin plate and is arranged with one end facing the fluorescence extraction surface. Although it was set slightly larger than the thickness of the scintillator, it was found that the fluorescence transmission efficiency was good. Specifically, the thickness dimension of the light guide is preferably 1.1 to 2.0 times, more strictly about 1.5 times the thickness dimension of the scintillator.
以上に述べた本発明によれば、その他の面を鏡面とし、当該その他の面と反射部材との間を離間させたことにより、その他の面での全反射を最大限に利用することができるようになり、蛍光を最大効率で蛍光取出面から導出することができるようになる。また、蛍光取出面を粗面としたことにより、表面仕上げ加工の手間を削減できるようになり、製造の簡単化やコストダウンに大幅に寄与し得る。 According to the present invention described above, the other surface is a mirror surface, and the other surface is separated from the reflecting member, so that the total reflection on the other surface can be utilized to the maximum. Thus, the fluorescence can be derived from the fluorescence extraction surface with maximum efficiency. In addition, by making the fluorescent light extraction surface rough, it is possible to reduce the effort of surface finishing, which can greatly contribute to simplification of manufacturing and cost reduction.
以下、本発明の一実施形態について図面を参照して説明する。 Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
本実施形態に係る放射線検出器１００は、γ線やβ線などの放射線を検出するものであり、図１、図２に示すように１層のシンチレータユニット１と、各シンチレータユニット１に取り付けられた受光機構２とを具備している。
各部について説明する。
The radiation detector 100 according to the present embodiment detects radiation such as γ rays and β rays, and is attached to each scintillator unit 1 and each scintillator unit 1 as shown in FIGS. 1 and 2. And a light receiving mechanism 2.
Each part will be described.
シンチレータユニット１は、図１、図２及び特に図３に示すように、例えば矩形（ここでは正方形）薄板状をなすシンチレータ１１と、該シンチレータ１１の各面板部、すなわち表裏面１１ａに対向して配置された薄膜状の一対の反射部材１２と、前記シンチレータ１１の外周縁部に配置されて当該シンチレータ１１を保持する矩形枠体１３とを具備したものである。 As shown in FIGS. 1, 2, and particularly FIG. 3, the scintillator unit 1 is opposed to, for example, a scintillator 11 having a rectangular (here, square) thin plate shape, and each face plate portion of the scintillator 11, that is, the front and back surfaces 11a. A pair of thin film-like reflecting members 12 disposed and a rectangular frame 13 that is disposed on the outer peripheral edge of the scintillator 11 and holds the scintillator 11 are provided.
前記シンチレータ１１は、図３に詳細を、図４に模式図を示すように、放射線が入射されると、その入射位置で蛍光（シンチレーション光）が生じるもので、ここでは例えばＮａＩを素材とする１ｍｍ程度の厚みの透明板である。このシンチレータ１１の面板部１１ａは、その表面粗さが蛍光を実質的に散乱させることなく略正反射する程度となるように鏡面加工されている。また、シンチレータ１１のその他の面、すなわち、四方全ての側端面１１ｂは、蛍光が実質的に散乱する粗さの面としてある。 As shown in detail in FIG. 3 and a schematic diagram in FIG. 4, the scintillator 11 generates fluorescence (scintillation light) at the incident position when radiation is incident. Here, for example, NaI is used as a material. It is a transparent plate having a thickness of about 1 mm. The face plate portion 11a of the scintillator 11 is mirror-finished so that the surface roughness thereof is approximately regular reflection without substantially scattering the fluorescence. The other surfaces of the scintillator 11, that is, the side end surfaces 11b on all four sides, are rough surfaces on which the fluorescence is substantially scattered.
反射部材１２は、図３に詳細を、図４に模式図を示すように、シンチレータ１１の面板部と略同じ大きさを有する薄膜であり、その反射面の素材には、前記蛍光をその波長の実質的な全帯域に亘って可及的に高い反射率で反射できるものを用いている。ちなみにこの実施形態での反射部材１２には、ＰＥＴフィルムを用いている。 As shown in detail in FIG. 3 and a schematic diagram in FIG. 4, the reflecting member 12 is a thin film having substantially the same size as the face plate portion of the scintillator 11. A material that can reflect with a reflectivity as high as possible over substantially the entire band is used. Incidentally, a PET film is used for the reflecting member 12 in this embodiment.
枠体１３は、図３に示すように、積層させた一対の枠体要素１３１からなる。枠体要素１３１は、例えばアクリル等の樹脂で形成された矩形枠状をなすものであり、その内周形状はシンチレータ１１の外周形状と略等しい矩形状に設定してある。この枠体要素１３１間には、枠体要素１３１と平面視略同一形状をなす薄い等厚板状の第１のライトガイド２１（詳細は後述する）が挟まれるようにして保持してあり、この第１のライトガイド２１の内周端面２１ａに、前記シンチレータ１１の側端面１１ｂが、シリコーン樹脂などの空気よりも屈折率の大きい粘弾性を有した透明の光学中継材４を介して接続してある。なお、この光学中継材４としては、シンチレータ１１とライトガイドとの屈折率の中間の屈折率を有するものが光伝達効率の観点からはより好ましい。 As shown in FIG. 3, the frame 13 includes a pair of frame elements 131 stacked. The frame element 131 has a rectangular frame shape formed of, for example, a resin such as acrylic, and the inner peripheral shape thereof is set to a rectangular shape that is substantially equal to the outer peripheral shape of the scintillator 11. Between the frame elements 131, a first light guide 21 (which will be described in detail later) is held so as to be sandwiched between the thin light-equivalent plate-like shapes that have substantially the same shape as the frame element 131 in plan view. The side end face 11b of the scintillator 11 is connected to the inner peripheral end face 21a of the first light guide 21 via a transparent optical relay material 4 having viscoelasticity having a refractive index larger than that of air such as silicone resin. It is. In addition, as this optical relay material 4, what has an intermediate refractive index of the scintillator 11 and a light guide is more preferable from a viewpoint of light transmission efficiency.
また、同図に示すように、各枠体要素１３１の対向面における内周端部には、所定距離だけ凹ませた段部１３２が形成してあり、この段部１３２の表面に設定した反射部材保持面１３２ａに、反射部材１２の周縁部が接着剤等で貼り付けてある。この構成によって、当該反射部材１２が、その反射面をシンチレータ１１の表裏面１１ａと平行でかつ一定距離だけ離間させて、この枠体１３に支持されるようにしてある。
なお、図３中、符号５は、シンチレータ１１を気密に覆って潮解等を防止するためのカバーであり、ここではアルミニウムの薄膜を用いているが、シンチレータがプラスティック製のものなど潮解性を有しない場合は、このカバーは不要となる。
Further, as shown in the figure, a stepped portion 132 that is recessed by a predetermined distance is formed at the inner peripheral end of the opposing surface of each frame element 131, and the reflection set on the surface of the stepped portion 132 is formed. The periphery of the reflecting member 12 is attached to the member holding surface 132a with an adhesive or the like. With this configuration, the reflecting member 12 is supported by the frame 13 with its reflecting surface parallel to the front and back surfaces 11a of the scintillator 11 and spaced apart by a certain distance.
In FIG. 3, reference numeral 5 denotes a cover for airtightly covering the scintillator 11 to prevent deliquescence and the like. Here, an aluminum thin film is used. If not, this cover is unnecessary.
受光機構２は、前記第１のライトガイド２１と、該第１のライトガイド２１の外周縁部にシリコーン樹脂などの光学中継材４を介して接続した第２のライトガイド２２と、該第２のライトガイド２２の外方端に臨ませて配置した受光素子２３とを具備したものである。 The light receiving mechanism 2 includes the first light guide 21, a second light guide 22 connected to the outer peripheral edge of the first light guide 21 via an optical relay material 4 such as silicone resin, and the second light guide 22. And a light receiving element 23 arranged facing the outer end of the light guide 22.
第１のライトガイド２１は、その厚み寸法が約１．５ｍｍの等厚透明板であり、前述したように、枠体要素１３１に挟み込まれて保持されている。なお、この実施形態では、図３に示すように、枠体要素１３１と第１のライトガイド２１との間に、シンチレータ１１に対して設けた反射部材１２と同じ第２の反射部材１２’を設けて、光の伝達効率向上を図っている。この第２の反射部材１２’は、第１のライトガイド２１と接着剤で接着されているが、その接着剤を部分的に設けるなどして、第２の反射部材１２’と第１のライトガイド２１との間に隙間ができるようにしている。また、第２の反射部材１２‘は、第１の反射部材１２と異なる材料を用いても構わない。 The first light guide 21 is an equal thickness transparent plate having a thickness dimension of about 1.5 mm, and is sandwiched and held between the frame elements 131 as described above. In this embodiment, as shown in FIG. 3, a second reflecting member 12 ′ that is the same as the reflecting member 12 provided for the scintillator 11 is provided between the frame element 131 and the first light guide 21. It is provided to improve the light transmission efficiency. The second reflecting member 12 ′ is bonded to the first light guide 21 with an adhesive, but the second reflecting member 12 ′ and the first light are partially provided with the adhesive. A gap is formed between the guide 21 and the guide 21. The second reflecting member 12 ′ may be made of a material different from that of the first reflecting member 12.
第２のライトガイド２２は、第１のライトガイド２１の外周４辺からそれぞれ外方に延びる矩形等厚透明板であり、ここでは、その厚みを第１のライトガイド２１と等しく設定してある。 The second light guide 22 is a rectangular equal-thickness transparent plate that extends outward from the four outer sides of the first light guide 21. Here, the thickness of the second light guide 22 is set equal to that of the first light guide 21. .
受光素子２３は例えばフォトディテクタであり、図１に示すように、第２のライトガイド２２の外方端部に複数が並べ設けてある。この受光素子２３と第２のライトガイド２２との間には、前記同様の光学中継材（図示しない）が充填されている。 The light receiving element 23 is, for example, a photodetector, and a plurality of the light receiving elements 23 are arranged at the outer end of the second light guide 22 as shown in FIG. The same optical relay material (not shown) is filled between the light receiving element 23 and the second light guide 22.
しかしてこのようなものであれば、図３に示すように、放射線照射によって生じたシンチレータ１１内の蛍光のうち、前記シンチレータ１１の表裏面１１ａに対して一定以上浅い角度で進むものは、当該表裏面１１ａが鏡面であり反射部材１２との間に空隙層が存在することから、この境界での屈折率の違いによって、１００％の効率で全反射される一方、それよりも深い角度で進入したものは、表裏面１１ａを抜けてその外側にある反射部材１２によって反射され、最終的にシンチレータ１１の側端面１１ｂ、すなわち蛍光取出面に導かれる。その後、蛍光は、ここから第１、第２のライトガイド２２を通って受光素子２３で検出される。 If this is the case, as shown in FIG. 3, among the fluorescence in the scintillator 11 generated by radiation irradiation, the one that proceeds at a shallow angle above the front and back surfaces 11a of the scintillator 11 Since the front and back surfaces 11a are mirror surfaces and there is a gap layer between the reflecting member 12 and the refractive index at this boundary, it is totally reflected with 100% efficiency, but enters at a deeper angle than that. Then, the light passes through the front and back surfaces 11a, is reflected by the reflecting member 12 outside, and is finally guided to the side end surface 11b of the scintillator 11, that is, the fluorescence extraction surface. Thereafter, the fluorescence is detected by the light receiving element 23 from here through the first and second light guides 22.
つまり、本実施形態によれば、所定割合の蛍光が、確実にシンチレータ１１の表裏面１１ａで全反射されることととなり、残りの空隙層に漏れた蛍光だけが反射部材１２で反射されることとなる。したがって、例えばシンチレータ１１の表面に反射部材を塗布したもののように、全ての蛍光を反射部材で反射するよりも反射効率が格段に向上し、その結果、蛍光を最大効率で蛍光取出面１１ｂから導出することができるようになる。 That is, according to the present embodiment, a predetermined proportion of the fluorescence is surely totally reflected by the front and back surfaces 11a of the scintillator 11, and only the fluorescence that has leaked into the remaining gap layer is reflected by the reflecting member 12. It becomes. Therefore, for example, the reflection efficiency is remarkably improved as compared with the case where all the fluorescence is reflected by the reflection member, such as a case where the reflection member is applied to the surface of the scintillator 11, and as a result, the fluorescence is derived from the fluorescence extraction surface 11b with the maximum efficiency. Will be able to.
また、蛍光取出面であるシンチレータ側端面１１ｂが粗面であるため、表面仕上げ加工の手間を削減できることによって、製造の簡単化やコストダウンに寄与し得る。しかも、このことは、光伝達を阻害する積極的な要因にはならず、むしろ本発明者による検討によれば、場合によっては鏡面よりも伝達効率が向上する可能性すらある。以下に、その検討結果を示す。
シンチレータの光取出面を鏡面にした場合、その外側に塗布されたシリコーン樹脂などの光学中継材に取り出すことができる到達光量率は、本発明者の理論計算によれば４６．９％、シミュレーションでは５８．５％である。
一方、シンチレータの光取出面を粗面にした場合、その粗面態様によって当該粗面での光吸収などによる損失が異なるので、横軸に、粗面での損失を考慮した光透過率、縦軸に光学中継材に取り出すことができる到達光量率をとってグラフに表すと、図５のようになる。
しかして、この図５から明らかなように、シンチレータの光取出面を粗面にした場合、その粗面での光吸収などによる損失が約２０〜３０％以下（粗面での光透過率が約７０〜８０％以上）となるような粗面態様にしておけば、鏡面を上回る効率で蛍光を取り出すことができる。
また、光取出面を粗面にした場合、図６に示すように、シンチレータの光屈折率が大きいほど、到達光量率は向上する。これは、鏡面の場合とは逆の傾向である。この技術によって屈折率の高い他のシンチレータ材料をより積極的に使用できるようになる。
Moreover, since the scintillator side end surface 11b which is a fluorescence extraction surface is a rough surface, it can contribute to simplification of manufacturing and cost reduction by reducing the work of surface finishing. In addition, this is not an active factor that inhibits light transmission. Rather, according to the study by the present inventor, there is a possibility that the transmission efficiency may be improved more than the mirror surface in some cases. The examination results are shown below.
When the light extraction surface of the scintillator is a mirror surface, the amount of reached light that can be extracted to an optical relay material such as silicone resin applied to the outside is 46.9% according to the theoretical calculation of the present inventor. 58.5%.
On the other hand, when the light extraction surface of the scintillator is a rough surface, the loss due to light absorption on the rough surface differs depending on the rough surface mode. FIG. 5 is a graph showing the ratio of the amount of light that can be extracted to the optical relay material on the axis.
As is apparent from FIG. 5, when the light extraction surface of the scintillator is made rough, the loss due to light absorption on the rough surface is about 20 to 30% or less (light transmittance on the rough surface is low). If it is made into the rough surface aspect which becomes about 70-80% or more), fluorescence can be taken out with the efficiency exceeding a mirror surface.
Further, when the light extraction surface is made rough, as shown in FIG. 6, the reached light amount ratio is improved as the light refractive index of the scintillator is increased. This is the opposite tendency to that of the mirror surface. This technique allows other scintillator materials with a higher refractive index to be used more aggressively.
なお、本発明は前記実施形態に限られない。例えば、図７、図８に示すように、第２のライトガイド２２を、受光素子２３との関係から、平面視徐々に幅が小さくなり、側面視徐々に厚みが大きくなるような異形状としてもよい。
また、シンチレータは、矩形平板状のものに限らず、円盤状のものでもよいし、ブロック状のものでもよい。蛍光取出面は、１面だけでも構わない。
受光素子もＰＭＴなど、種々のタイプのものを用いることができる。
その他、本発明の趣旨に反しない限りにおいて、様々な変形や実施形態の組み合わせを行っても構わない。
The present invention is not limited to the above embodiment. For example, as shown in FIGS. 7 and 8, the second light guide 22 has an irregular shape that gradually decreases in width in plan view and gradually increases in thickness in side view due to the relationship with the light receiving element 23. Also good.
Further, the scintillator is not limited to a rectangular flat plate shape, and may be a disk shape or a block shape. The fluorescence extraction surface may be only one surface.
Various types of light receiving elements such as PMT can be used.
In addition, various modifications and combinations of embodiments may be performed without departing from the spirit of the present invention.
１００・・・放射線検出器
１１・・・シンチレータ
１１ａ・・・その他の面（表裏面）
１１ｂ・・・蛍光取出面（側端面）
１２・・・反射部材
２・・・受光機構
２１・・・ライトガイド（第１のライトガイド）
２２・・・ライトガイド（第２のライトガイド）
100 ... Radiation detector 11 ... Scintillator 11a ... Other surface (front and back)
11b: Fluorescence extraction surface (side end surface)
12 ... Reflecting member 2 ... Light receiving mechanism 21 ... Light guide (first light guide)
22 ... Light guide (second light guide)
Claims (3)
前記蛍光取出面に臨ませて配置した受光機構と、
前記その他の面に対向させつつ一定距離離間させて配置した反射部材とを具備し、
前記反射部材と前記その他の面との間に空隙層が設けられており、
前記シンチレータが板状又は円盤状をなすものであり、該シンチレータの表裏両面を前記その他の面とするとともに、側端面を蛍光取出面とし、
前記受光機構が、受光素子と、前記蛍光取出し面と前記受光素子との間に設けられたライトガイドを具備し、
前記シンチレータの対向する一対の側端面がそれぞれ前記ライトガイドと接着されており、
前記ライトガイドにおいて前記その他の面と同じ方向を向く面に対向して第２の反射部材が設けられていることを特徴とする放射線検出器。 A scintillator in which one or more of the surfaces are set as a fluorescence extraction surface, the other surface is a mirror surface, and the fluorescence extraction surface is a rough surface having a rougher surface than the other surfaces;
A light receiving mechanism arranged facing the fluorescent light extraction surface;
A reflective member disposed at a constant distance while facing the other surface, and
A gap layer is provided between the reflecting member and the other surface ,
The scintillator is plate-shaped or disk-shaped, and both the front and back surfaces of the scintillator are the other surface, and the side end surface is a fluorescence extraction surface,
The light receiving mechanism comprises a light receiving element, a light guide provided between the fluorescence extraction surface and the light receiving element,
A pair of opposing side end surfaces of the scintillator are respectively bonded to the light guide,
A radiation detector , wherein a second reflecting member is provided facing a surface facing the same direction as the other surface in the light guide .
The light receiving mechanism includes a light guide having a thin plate shape of equal thickness and having one end opposed to the fluorescence extraction surface, and a light receiving element disposed facing the other end of the light guide, 3. The radiation detector according to claim 2, wherein the thickness dimension is set larger than the thickness dimension of the scintillator.
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