JP3984110B2

JP3984110B2 - Radiation detector

Info

Publication number: JP3984110B2
Application number: JP2002172364A
Authority: JP
Inventors: 彰柚木
Original assignee: Toshiba Corp
Current assignee: Toshiba Corp
Priority date: 2002-06-13
Filing date: 2002-06-13
Publication date: 2007-10-03
Anticipated expiration: 2022-06-13
Also published as: JP2004020249A

Description

【０００１】
【発明の属する技術分野】
本発明は、例えば原子力施設等で使用されるガス電離箱を使用したγ線を測定する放射線検出装置に関するものである。
【０００２】
【従来の技術】
従来から、一般公衆の外部被曝を評価することを目的として、原子力発電所等の原子力施設がある地域、地方にγ線検出器を設置し、バックグランドレベルから事故時の高レベルまでのγ線の常時監視を行っている。そこで使用されるγ線検出器はバックグランドレベルから事故時の高い放射線レベルまで広いダイナミックレンジにわたって連続的に測定できなければならない。さらに人間の外部被曝の評価に使用することからレスポンスのエネルギー特性も厳しいものとなり、測定対象が環境γ線であることから報告特性も４π方向に対して一様であることが要求されている。このため従来はアルゴンガス等の不活性ガスを封入した容器内に中心電極を設け、容器内に放射線が入射するとガスが電離しイオンを発生し、中心電極から流れる電流を検出することにより放射線の強度、線量、エネルギーを測定する球形のガス電離箱を使用している。
【０００３】
図１２にこの種の放射線検出器に使用される従来の球形のガス電離箱の構成例を示す。図１２においてガス電離箱１には検出ガス２が封入され、ガス電離箱１内に設けられた中心電極３からの出力電流は微少電流測定回路４によって測定される。
【０００４】
【発明が解決しようとする課題】
ガス電離箱１から得られる出力信号は小さいため、バックグランドレベルにおいても測定可能な電流が得られるように設計すると、事故時に想定される高レベルγ線の照射時に電荷収集が飽和してしまう恐れがあるためガス電離箱１の測定ダイナミックレンジを広げる必要があった。
【０００５】
また、ガス電離箱１では軽量であること、および処理が不要であることから検出器容器の材料としてアルミニウムが使用されることが多い。しかしながらアルミニウムはα線を出す放射性同位元素を比較的多く含むことからバックグランドレベルに匹敵する電離電流が生じてしまう。このためα線バックグランドを低減することが必要であった。
【０００６】
本発明は、以上の課題を解決し、測定ダイナミックレンジが広い放射線検出装置を提供することを目的とする。
【０００７】
【課題を解決するための手段】
上記目的を達成するために請求項１に記載の放射線検出装置の発明は、検出ガスを封入した導電性容器と、前記導電性容器から電気的に絶縁されながら前記導電性容器を気密に貫通して前記導電性容器内に設けられた電極支柱部と、前記電極支柱部の先端に位置し前記電極支柱部から絶縁されながら前記電極支柱部の先端部を覆う電極末端部と、前記電極支柱部と前記電極末端部とに接続された電離電流測定回路とからなることを特徴とする。
【０００８】
この発明によれば、ガス電離箱からの信号を電極支柱部からと電極末端部とから分けて測定し、同一検出器内の信号から線量直線性の良い部分を抜き出して測定する。
【０００９】
請求項２に記載の放射線検出装置の発明は、検出ガスを封入した導電性容器と、前記導電性容器から電気的に絶縁されながら前記導電性容器を気密に貫通して前記導電性容器内に設けられた筒状の電極支柱部と、前記電極支柱部の先端に位置し前記電極支柱部から絶縁されながら前記電極支柱部の先端部を覆う電極末端部と、前記電極支柱部の筒内を通って前記電極末端部と電気的に接続され前記導電性容器を貫通する電流導入端子と、前記電極支柱部と前記電極末端部とに接続された電離電流測定回路とからなることを特徴とする。
この発明によれば、電極末端部からの信号への電界集中を防ぎ、線量直線性を高線量まで延ばす。
【００１０】
請求項３に記載の放射線検出装置の発明は、検出ガスを封入した導電性容器と、前記導電性容器から電気的に絶縁されながら前記導電性容器を気密に貫通して前記導電性容器内に設けられた電極支柱部と、前記電極支柱部の先端に位置し前記電極支柱部から絶縁されながら前記電極支柱部の先端部を覆う電極末端部と、前記電極支柱部に接続された第１の電離電流測定回路と、前記電極末端部に接続された第２の電離電流測定回路と、前記第１の電離電流測定回路及び前記第２の電離電流測定回路に各々接続され且つ前記第１の電離電流測定回路からの出力と前記第２の電離電流測定回路からの出力とを比較する電離電流比較回路と、前記第１の電離電流測定回路と前記第２の電離電流測定回路に接続された信号切替補正回路と、からなる放射線検出器であって、前記信号切替補正回路は、前記電離電流比較回路からの情報に基づいて前記第１の電離電流測定回路からの出力を使うのか前記第２の電離電流測定回路からの出力を使うのか、または前記第１の電離電流測定回路からの出力と前記第２の電離電流測定回路との出力を重み付けをして加え合わせたものを使うのかを選択する選択回路を有することを特徴とする。
【００１１】
この発明によれば、第１の電離電流測定回路と第２の電離電流測定回路との出力を比較することにより、電極末端部における電流の飽和度が分かり、その情報を用いて信号切替補正回路において、第１の電離電流測定回路からの信号を使うのか、第２の電離電流測定回路からの信号を使うのか、第１の電離電流測定回路と第２の電離電流測定回路との出力に重み付けをして加え合わせたものを使うのかを選択する。
【００１２】
請求項４に記載の放射線検出装置の発明は、検出ガスを封入した導電性容器と、前記導電性容器から電気的に絶縁されながら前記導電性容器を気密に貫通して前記導電性容器内に設けられた筒状の電極支柱部と、前記電極支柱部の先端に位置し前記電極支柱部から絶縁されながら前記電極支柱部の先端部を覆う電極末端部と、前記電極支柱部の筒内を通って前記電極末端部と電気的に接続され前記導電性容器を貫通する電流導入端子と、前記電極支柱部に接続された第１の電離電流測定回路と、前記電極末端部に接続された第２の電離電流測定回路と、前記第１の電離電流測定回路及び前記第２の電離電流測定回路に各々接続され且つ前記第１の電離電流測定回路からの出力と前記第２の電離電流測定回路からの出力とを比較する電離電流比較回路と、前記第１の電離電流測定回路と前記第２の電離電流測定回路に接続された信号切替補正回路と、からなる放射線検出器であって、前記信号切替補正回路は、前記電離電流比較回路からの情報に基づいて前記第１の電離電流測定回路からの出力を使うのか前記第２の電離電流測定回路からの出力を使うのか、または前記第１の電離電流測定回路からの出力と前記第２の電離電流測定回路との出力を重み付けをして加え合わせたものを使うのかを選択する選択回路を有することを特徴とする。
【００１３】
この発明によれば、第１の電離電流測定回路と第２の電離電流測定回路との出力を比較することにより、電極末端部における電流の飽和度が分かり、その情報を用いて信号切替補正回路において、第１の電離電流測定回路からの信号を使うのか、第２の電離電流測定回路からの信号を使うのか、第１の電離電流測定回路と第２の電離電流測定回路との出力に重み付けをして加え合わせたものを使うのかを選択する。
【００１４】
請求項５に記載の放射線検出装置の発明は、請求項１乃至４のいずれかに記載の放射線検出装置において、前記電極末端部は丸いキャップ状の形状であり、前記電極支柱部は円筒状の形状であり、前記電極末端部が前記電極支柱部より大きな曲率半径を有することを特徴とする。
この発明によれば、電極末端部への泳動電子の集中を緩和し、高線量照射時の飽和特性が改善され、広いダイナミックレンジにわたって直線性を保つ。
【００１９】
【発明の実施の形態】
以下本発明の実施の形態について図面を参照して説明する。図１は本発明の第1の実施の形態を示す図で、検出ガス２を封入したガス電離箱１の導電性容器５から絶縁板６によって電気的に絶縁された中心電極の電極支柱部７が導電性容器５を気密に貫通して導電性容器５のほぼ中心部まで突き出して設けられている。電極支柱部７の先端には丸いキャップ状の電極末端部８があり電極支柱部７から絶縁されながら電極支柱部７の先端部を覆っている。電極末端部８は導電性容器５を貫通する電流導入端子９とリード線１０を介して電気的に接続され、電極支柱部７と電極末端部８とはそれぞれ電離電流測定回路１１に接続されている。電極末端部８の外側は球形で、内側は円柱状の電極支柱部７が差し込めるような穴が明けられた構造と成っている。
【００２０】
このような構成の本発明の第１の実施の形態による放射線検出装置であると、導電性容器５内で発生した電荷は、導電性容器５と電極支柱部７、あるいは電極末端部８との間に加えられた電気力線に沿って泳動する。一方電気力線は電極支柱部７より電極末端部８に集中する。そのため泳動する電子は電極末端部８に多く集まることになる。電子親和性の不純物ガスが検出ガス２に含まれると泳動電子を捕獲して負イオンとなりやすい。そうすると泳動速度が１０００分の１程度に遅くなり、見かけ上電極周辺に空間電荷層として蓄積する。この空間電荷層は照射線量が大きくなるとともに大きくなり、電極近傍の電界を小さくすることになり、泳動電子の捕獲、再結合を促進する。従って電極支柱部７に集められる電荷量は電極末端部８に集められる電荷量より飽和特性が良く、より高い照射線量に対してまで照射線量に対する出力電流の直線性が確保される。電極支柱部７に集められた電荷は、電離電流測定回路１１に入力され電流量が測定される。電極末端部８に集められた電荷は、電流導入端子９を通して、電離電流測定回路１１に入力され電流量が測定される。そのため電極支柱部７からの電離電流値は電極末端部８からの電離電流値より飽和特性が良く、より高い照射線量に対してまで照射線量に対する出力電流の直線性が確保されることになる。
【００２１】
このようにガス電離箱１からの信号を電極支柱部７からと電極末端部８とから分けて測定することで、同一検出器内の信号から線量直線性の良い部分を抜き出すことができ、測定のダイナミックレンジを拡大することができる。
【００２２】
次に本発明の第２の実施の形態について図２を参照して説明する。図２において図１と同一部分は同一の符号を付し、詳細な説明は省略する。図２において、電極支柱部７を円筒状に形成し、電極末端部８に接続される電流導入端子９を電極支柱部７の先端開口部から円筒内部を通して電極支柱部７とは絶縁紙ながら導電性容器５の外部に引き出している。
【００２３】
このような構成の本発明の第２の実施の形態による放射線検出装置であると、電極末端部８からの信号への電界の集中がないため、電極支柱部７でより高線量まで電荷収集効率が下がらず、飽和特性が改善され、照射線量に対する直線性が高線量にまで伸び、直線性が改善される。
【００２４】
次に本発明の第３の実施の形態について図３を参照して説明する。図３において図１と同一部分は同一の符号を付し、詳細な説明は省略する。図３において、第１、第２の実施の形態で示す電離電流測定回路１１の代わりに電極支柱部７からの電離電流を測定する第１の電離電流測定回路１２と、電極末端部８からの電離電流を測定する第２の電離電流測定回路１３と、第１の電離電流測定回路１２の出力と第２の電離電流測定回路１３の出力とを比較する電離電流比較回路１４とを設け、さらにそれらに接続された信号切替補正回路１５とを設ける。信号切替補正回路１５の内部には信号切替補正回路１５の出力として、第1の電離電流測定回路１２からの信号を使うのか、第２の電離電流測定回路１３からの信号を使うのか、または第１の電離電流測定回路１２と第２の電離電流測定回路１３との出力に重み付けをして加え合わせたものを使うのかを選択する選択回路が含まれている。
【００２５】
このような構成の本発明の第３の実施の形態による放射線検出装置であると、第１の電離電流測定回路１２と第２の電離電流測定回路１３との出力を比較することにより、電極末端部８における電流の飽和度が分かる。その情報を用いて信号切替補正回路１５において、第１の電離電流測定回路１２からの信号を使うのか、第２の電離電流測定回路１３からの信号を使うのか、第１の電離電流測定回路１２と第２の電離電流測定回路１３との出力に重み付けをして加え合わせたものを使うのかが選択される。これにより、放射線検出装置としての１個の出力について電離電流信号出力が広いダイナミックレンジにわたって直線性を保つことが出来る。
【００２６】
次に本発明の第４の実施の形態について図４を参照して説明する。図４において図３と同一部分は同一の符号を付し、詳細な説明は省略する。図４においては、図２に示す電極構造に対して図３に示す電離電流比較回路１４と信号切替補正回路１５とを設けた例で作用効果は図３に示す第三の実施の形態と同様の作用効果が得られる。
【００２７】
次に本発明の第５の実施の形態について図５を参照して説明する。図５において、電極末端部８の曲率半径を電極支柱部７の半径より大きくする。
このような構成の本発明の第５の実施の形態による放射線検出装置であると、電極末端部８への泳動電子の集中が緩和されるため、高線量照射時の飽和特性が改善され、さらに広いダイナミックレンジにわたって直線性を保つことができる。
【００２８】
次に本発明の第６の実施の形態について図６を参照して説明する。図６において、電極表面近傍での電界強度が電極末端部８と電極支柱部７とで同程度になるよう、電極末端部８の曲率半径を大きくする。そして電極末端部８は電極支柱部７に電気的に接続するかあるいは一体のものとして構成し、その出力を電離電流測定回路に接続する。
【００２９】
このような構成の本発明の第６の実施の形態による放射線検出装置であると、電極末端部８への泳動電子の集中が緩和され、高線量照射時の飽和特性が改善されるうえに、電離電流測定回路が電離箱１個につき１系統が必要されるだけとなり、より簡素化した測定システムとなる。
【００３０】
次に本発明の第７の実施の形態について図７を参照して説明する。図７において図１と同一部分は同一の符号を付し、詳細な説明は省略する。図７において、検出ガス２を封入した導電性容器５から電気的に絶縁された電極支柱部７が導電性容器５を気密に貫通して導電性容器５のほぼ中心部まで突き出して設けられている。電極支柱部７の先端には丸いキャップ状の電極末端部８があって電極支柱部７から絶縁されながら電極支柱部７の先端部を覆っている。電極末端部８は導電性容器５を貫通する電流導入端子９とリード線１０を介して電気的に接続され、電極支柱部７と電極末端部８とはそれぞれ電離電流測定回路１１に接続されている。電極末端部８の外側は球形で、内側は円柱状の電極支柱部７が差し込めるような穴が明けられた構造と成っている。
【００３１】
このようなガス電離箱１において酸素分子および窒素酸化物を吸着する能力を持ったガス吸着剤１６を導電性容器５内に設けている。ガス吸着剤１６の形状および導電性容器５内での取り付け位置は適宜任意である。
【００３２】
このような構成の本発明の第７の実施の形態による放射線検出装置であると、泳動電子は検出ガス２中に含まれる酸素分子や窒素酸化物のように電子親和性の大きい不純物に捕獲されることで空間電荷層を形成するようになる。導電性容器５内で発生した電荷は、導電性容器５と電極支柱部７あるいは電極末端部８との間に加えられた電気力線に沿って泳動する。一方電気力線は電極支柱部７より電極末端部８に集中する。そのため泳動する電子は電極末端部８に多く集まることになる。電子親和性の不純物ガスが検出ガス２中に含まれると泳動電子を捕獲して負イオンとなりやすい。そうすると泳動速度が１０００分の１程度に遅くなり、見かけ上電極周辺に空間電荷層として蓄積する。この空間電荷層は照射線量が大きくなるとともに大きくなり、電極近傍の電界を小さくすることになり、泳動電子の捕獲、再結合を促進する。従って電極支柱部７に集められる電荷量は電極末端部８に集められる電荷量より飽和特性が良く、より高い照射線量に対してまで照射線量に対する出力電流の直線性が確保される。電極支柱部７に集められた電荷は、電離電流測定回路１１に入力され電流量が測定される。電極末端部８に集められた電荷は、電流導入端子９を通して、電離電流測定回路１１に入力され電流量が測定される。そのため電極支柱部７からの電離電流値は電極末端部８からの電離電流値より飽和特性が良く、より高い照射線量に対してまで照射線量に対する出力電流の直線性が確保されることになる。
【００３３】
このように、検出ガス２中の不純物が少なくなることで泳動電子の捕獲が減り、電荷収集率の飽和特性が改善され、照射線量に対するダイナミックレンジを拡大することができる。
【００３４】
次に本発明の第８の実施の形態について図８を参照して説明する。図８において図１と同一部分は同一の符号を付し、詳細な説明は省略する。図８において、不活性ガスを主成分とした検出ガス２を封入した導電性容器５から絶縁蓋６によって電気的に絶縁された電極７ａが導電性容器５を気密に貫通して導電性容器５のほぼ中心部まで突き出して設けられている。導電性容器５に透明な窓１７を気密に設け、その窓１７の外側に光検出器１８を取り付ける。窓１７の材質は検出ガス２のシンチレーション光を透過する材質とし、真空紫外光の場合のように透過する材質が入手し難い場合は窓１７の導電性容器５内側にサイリチルサンメチルやＰＯＰＯＰのような波長変換物質１９を塗布する。光検出器１８の出力は一般的な微少電流測定回路またはパルス計数回路２０に入力される。また、導電性容器５内の電極７ａからの信号は電離電流測定回路１１に入力される。さらに一般的な微少電流測定回路またはパルス計数回路２０と電離電流測定回路１１との出力は光検出系の信号に基づいて電離電流測定回路１１の出力を補正する出力補正回路２１に入力される。
【００３５】
このような構成の本発明の第８の実施の形態による放射線検出装置であると、検出ガス２のシンチレーション光は電離に至るまでエネルギーを付与されなかった検出ガス２の分子、あるいは一旦は電離したものの再結合した検出ガス２のイオンによって発生する。従って電極７ａ近傍の空間電荷層により電子泳動が滞留すると、滞留した電子は電極７ａに達する前に再結合する確率が大きくなる。従来の検出器では電極に達しない電子を測定することはできなかったが、本発明による検出装置においては再結合した電子はシンチレーション光として光検出器１８により検出可能になる。電極７ａにより測定される電離電流をＩ、シンチレーション光を測定した光検出器１８からの出力電流等をＳ、放射線により付与されたエネルギーをＥとすると、補正係数をαと換算係数βを用いて、Ｅ＝β（Ｉ＋αＳ）と表されることが実験的に示されているので出力補正回路２１においてＥ＝β（Ｉ＋αＳ）と同様の補正をすることにより、電荷収集の飽和を補正することが可能になり、再結合電子が線量測定に寄与することで、電荷収集率の飽和特性を補正により改善することができ、照射線量に対するダイナミックレンジを拡大することができる。
【００３６】
次に本発明の第９の実施の形態について図９を参照して説明する。図９において図８と同一部分は同一の符号を付し、詳細な説明は省略する。図９において、光検出器１８の出力は電流測定回路２２、パルス波形弁別回路２３およびパルス計数回路２４を介してγ線識別計数回路２５に接続される。電極および電離電流測定回路は設けない。
【００３７】
このような構成の本発明の第９の実施の形態による放射線検出装置であると、γ線に起因する２次電子と検出ガス２との相互作用によるものに比べて、α線や宇宙線と検出ガス２との相互作用によるものは、検出ガス２のシンチレーション光のパルス減衰時間が短い。そこでパルス波形弁別回路２３で２次電子によるシンチレーションとα線、宇宙線によるシンチレーションを識別する。一方パルス計数回路２４では放射線の種別を区別せずに計数している。そこでγ線識別計数回路２５に放射線種類と計数に関する情報を供給することで、γ線識別計数回路２５はガンマ線のみの計数を行うことが可能になる。
【００３８】
したがって、このような構成の放射線検出装置であると、γ線による信号のみを識別して線量測定を行うことで、導電性容器５に起因するα線バックグランド等のバックグランドの影響を排除し低バックグランドの測定が行える。
【００３９】
次に本発明の第１０の実施の形態について図１０を参照して説明する。図１０において図８と同一部分は同一の符号を付し、詳細な説明は省略する。図１０において、導電性容器５を気密に貫通して導電性容器５のほぼ中心部まで突き出して設けられた電極７ａが電離電流測定回路１１、パルス計数回路２４とパルス電荷量測定回路２６に接続される。パルス電荷量測定回路２６の出力は、パルス計数回路２４の出力と共に電荷量、電流換算回路２７に入力される。電荷量、電流換算回路２７の出力は、電離電流測定回路１１の出力とともに出力電流補正回路２８に入力され、電離電流測定回路１１の出力から電荷量、電流換算回路２７の出力が差し引かれる。
【００４０】
このような構成の本発明の第１０の実施の形態による放射線検出装置であると、第９の実施の形態で説明したしたパルス計数により、α線等パルス幅が比較的短い信号の発生電荷量および発生頻度を測定できる。従って電荷量、電流変換回路２７の出力は、主にα線に起因するバックグランド電流となる。従って出力電流補正回路２８において電離電流測定回路１１の出力から電荷量、電流換算回路２７の出力を差し引くことで、当該バックグランド電流の補正が行え、導電性容器５に起因するα線バックグランド等のバックグランドの影響を排除し低バックグランドの測定が行える。
【００４１】
次に本発明の第１１の実施の形態について図１１を参照して説明する。図１１において図８と同一部分は同一の符号を付し、詳細な説明は省略する。図１１において、光検出器１８の出力は電流測定回路２２、パルス波形弁別回路２３およびパルス計数回路２４を介しγ線識別計数回路２５に入力される。電離電流測定回路１１については、導電性容器５を気密に貫通して導電性容器５のほぼ中心部まで突き出して設けられた電極７ａと接続されている。さらに、光検出器１８の信号に基づいてγ線以外の放射線による発生電荷量を計算する電流計算回路２９と、電流計算回路２９の出力と電離電流測定回路１１の出力とを用いて電離電流測定回路１１の出力を補正する出力補正回路３０を設ける。
【００４２】
このような構成の本発明の第１１の実施の形態による放射線検出装置であると、第９の実施の形態で説明したγ線識別によりγ線以外の放射線による計数値が求まる。この結果に基づき電流計算回路２９において、γ線以外の放射線の入射によって発生する平均的な電流値を計算する。得られた電流値を出力補正回路３０に入力し、電離電流測定回路１１の出力から差し引くことにより、γ線のみの寄与による電離電流値を求めることができ、γ線による信号のみを識別して線量測定を行う事で、導電性容器５に起因するα線バックグランド等のバックグランドの影響を排除し低バックグランドの測定が行える。
【００４３】
【発明の効果】
以上説明したように本発明によれば、検出ガスを封入した導電性容器と、導電性容器から電気的に絶縁されながら導電性容器を気密に貫通して導電容器内に設けられた電極支柱部と、電極支柱部の先端に位置し電極支柱部から絶縁されながら電極支柱部の先端部を覆う電極末端部と、電極支柱部と電極末端部とに接続された電離電流測定回路とから構成したので、測定ダイナミックレンジが広い放射線検出装置を提供することができる。
【図面の簡単な説明】
【図１】本発明の第１の実施の形態による放射線検出装置を示すブロック構成図。
【図２】本発明の第２の実施の形態による放射線検出装置を示すブロック構成図。
【図３】本発明の第３の実施の形態による放射線検出装置を示すブロック構成図。
【図４】本発明の第４の実施の形態による放射線検出装置を示すブロック構成図。
【図５】本発明の第５の実施の形態による放射線検出装置を示すブロック構成図。
【図６】本発明の第６の実施の形態による放射線検出装置を示すブロック構成図。
【図７】本発明の第７の実施の形態による放射線検出装置を示すブロック構成図。
【図８】本発明の第８の実施の形態による放射線検出装置を示すブロック構成図。
【図９】本発明の第９の実施の形態による放射線検出装置を示すブロック構成図。
【図１０】本発明の第１０の実施の形態による放射線検出装置を示すブロック構成図。
【図１１】本発明の第１１の実施の形態による放射線検出装置を示すブロック構成図。
【図１２】従来の放射線検出装置を示すブロック構成図。
【符号の説明】
１…ガス電離箱、２…検出ガス、５…導電性容器、７…電極支柱部、７ａ…電極、８…電極末端部、９…電流導入端子、１１…電離電流測定回路、１２…第１の電離電流測定回路、１３…第２の電離電流測定回路、１４…電離電流比較回路、１５…信号切替補正回路、１６…ガス吸着材、１７…窓、１８…光検出器、１９…波長変換物質、２０…微少電流測定回路またはパルス計数回路、２１…出力補正回路、２２…電流測定回路、２３…パルス波形弁別回路、２４…パルス計数回路、２５…γ線識別計数回路、２６…パルス電荷量測定回路、２７…電荷量、電流換算回路、２８…出力電流補正回路、２９…電流計算回路、３０…出力補正回路。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a radiation detection apparatus for measuring γ rays using a gas ionization chamber used in, for example, a nuclear facility.
[0002]
[Prior art]
Conventionally, for the purpose of evaluating external exposure to the general public, γ-ray detectors have been installed in areas and regions where nuclear facilities such as nuclear power plants are located, and from the background level to the high level at the time of the accident. Is constantly monitored. The γ-ray detector used there must be able to measure continuously over a wide dynamic range from the background level to the high radiation level at the time of the accident. Furthermore, since it is used for the evaluation of human external exposure, the response energy characteristics are severe, and since the measurement object is environmental γ-rays, the reporting characteristics are required to be uniform in the 4π direction. For this reason, conventionally, a central electrode is provided in a container filled with an inert gas such as argon gas, and when radiation enters the container, the gas is ionized to generate ions, and the current flowing from the central electrode is detected to detect the radiation. A spherical gas ionization chamber that measures intensity, dose, and energy is used.
[0003]
FIG. 12 shows a configuration example of a conventional spherical gas ionization chamber used in this type of radiation detector. In FIG. 12, the gas ionization chamber 1 is filled with a detection gas 2, and the output current from the center electrode 3 provided in the gas ionization chamber 1 is measured by the minute current measuring circuit 4.
[0004]
[Problems to be solved by the invention]
Since the output signal obtained from the gas ionization chamber 1 is small, if it is designed so that a measurable current can be obtained even at the background level, there is a risk that charge collection will be saturated at the time of high-level γ-ray irradiation assumed at the time of an accident. Therefore, it was necessary to widen the measurement dynamic range of the gas ionization chamber 1.
[0005]
In addition, since the gas ionization chamber 1 is lightweight and does not require processing, aluminum is often used as a material for the detector container. However, since aluminum contains a relatively large amount of radioactive isotopes that emit α-rays, an ionization current comparable to the background level is generated. For this reason, it was necessary to reduce the α-ray background.
[0006]
The present invention solves the above problems and widens the measurement dynamic range. Free An object is to provide a ray detection device.
[0007]
[Means for Solving the Problems]
In order to achieve the above object, the invention of the radiation detection apparatus according to claim 1 comprises a conductive container enclosing a detection gas, Said While being electrically insulated from the conductive container Said Airtightly penetrate the conductive container Said Conductive sex An electrode support provided in the container; Said Located at the tip of the electrode post Said While insulated from the electrode column Said An electrode end portion covering the tip of the electrode support, Said Electrode support and Said And an ionization current measuring circuit connected to the electrode end.
[0008]
According to the present invention, the signal from the gas ionization chamber is measured separately from the electrode support column and the electrode end, and a portion having good dose linearity is extracted from the signal in the same detector.
[0009]
The invention of the radiation detection apparatus according to claim 2 includes a conductive container enclosing a detection gas, Said While being electrically insulated from the conductive container Said Airtightly penetrate the conductive container Said Conductive sex A cylindrical electrode support provided in the container; Said Located at the tip of the electrode post Said While insulated from the electrode column Said An electrode end portion covering the tip of the electrode support, Said Through the inside of the electrode column Said Electrically connected to the end of the electrode Said A current introduction terminal penetrating the conductive container; Said Electrode support and Said And an ionization current measuring circuit connected to the electrode end.
According to the present invention, electric field concentration on the signal from the electrode end is prevented, and the dose linearity is extended to a high dose.
[0010]
The invention of a radiation detection device according to claim 3 is a conductive container enclosing a detection gas; Said While being electrically insulated from the conductive container Said Airtightly penetrate the conductive container Said Conductive sex An electrode support provided in the container; Said Located at the tip of the electrode post Said While insulated from the electrode column Said An electrode end portion covering the tip of the electrode support, A first ionization current measurement circuit connected to the electrode support, a second ionization current measurement circuit connected to the electrode end, the first ionization current measurement circuit, and the second ionization current measurement; The output from the first ionization current measurement circuit and the output from the second ionization current measurement circuit are respectively connected to the circuit and compared with the output from the second ionization current measurement circuit An ionization current comparison circuit; In the first ionization current measurement circuit and the second ionization current measurement circuit Connected signal switching correction circuit and The signal switching correction circuit uses the output from the first ionization current measurement circuit based on the information from the ionization current comparison circuit, or the second ionization current measurement circuit. And a selection circuit for selecting whether to use a weighted output of the output from the first ionization current measurement circuit and the output from the second ionization current measurement circuit. That Features.
[0011]
According to the present invention, by comparing the outputs of the first ionization current measurement circuit and the second ionization current measurement circuit, the degree of saturation of the current at the end of the electrode can be found, and the signal switching correction circuit is obtained using the information. , Whether to use the signal from the first ionization current measurement circuit or the signal from the second ionization current measurement circuit, weights the outputs of the first ionization current measurement circuit and the second ionization current measurement circuit And select whether to use the added one.
[0012]
The invention of the radiation detection apparatus according to claim 4 , A conductive container filled with a detection gas; Said While being electrically insulated from the conductive container Said Airtightly penetrate the conductive container Said Conductive sex A cylindrical electrode support provided in the container; Said Located at the tip of the electrode post Said While insulated from the electrode column Said An electrode end portion covering the tip of the electrode support, Said Through the inside of the electrode column Said Electrically connected to the end of the electrode Said A current introduction terminal penetrating the conductive container; A first ionization current measurement circuit connected to the electrode support, a second ionization current measurement circuit connected to the electrode end, the first ionization current measurement circuit, and the second ionization current measurement; The output from the first ionization current measurement circuit and the output from the second ionization current measurement circuit are respectively connected to the circuit and compared with the output from the second ionization current measurement circuit An ionization current comparison circuit; In the first ionization current measurement circuit and the second ionization current measurement circuit Connected signal switching correction circuit and The signal switching correction circuit uses the output from the first ionization current measurement circuit based on the information from the ionization current comparison circuit, or the second ionization current measurement circuit. And a selection circuit for selecting whether to use a weighted output of the output from the first ionization current measurement circuit and the output from the second ionization current measurement circuit. thing It is characterized by.
[0013]
According to the present invention, by comparing the outputs of the first ionization current measurement circuit and the second ionization current measurement circuit, the degree of saturation of the current at the end of the electrode can be found, and the signal switching correction circuit is obtained using the information. , Whether to use the signal from the first ionization current measurement circuit or the signal from the second ionization current measurement circuit, weights the outputs of the first ionization current measurement circuit and the second ionization current measurement circuit And select whether to use the added one.
[0014]
The invention of a radiation detection apparatus according to claim 5 is the radiation detection apparatus according to any one of claims 1 to 4, The electrode end portion has a round cap shape, and the electrode support portion has a cylindrical shape, The electrode end is Said From electrode support Big It has a large curvature radius.
According to the present invention, the concentration of electrophoretic electrons at the electrode end is alleviated, the saturation characteristics during high-dose irradiation are improved, and linearity is maintained over a wide dynamic range.
[0019]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a diagram showing a first embodiment of the present invention. An electrode column portion 7 of a central electrode electrically insulated by an insulating plate 6 from a conductive container 5 of a gas ionization chamber 1 in which a detection gas 2 is enclosed. Are provided so as to penetrate the conductive container 5 in an airtight manner and protrude almost to the center of the conductive container 5. A round cap-shaped electrode terminal 8 is provided at the tip of the electrode support 7, and covers the tip of the electrode support 7 while being insulated from the electrode support 7. The electrode end portion 8 is electrically connected to the current introduction terminal 9 penetrating the conductive container 5 via the lead wire 10, and the electrode strut portion 7 and the electrode end portion 8 are respectively connected to the ionization current measuring circuit 11. Yes. The outer side of the electrode terminal part 8 is spherical, and the inner side has a structure in which a hole into which the cylindrical electrode support part 7 can be inserted is formed.
[0020]
In the radiation detection apparatus according to the first embodiment of the present invention having such a configuration, the electric charge generated in the conductive container 5 is generated between the conductive container 5 and the electrode support 7 or the electrode end 8. It migrates along the electric lines of force applied between them. On the other hand, the electric lines of force are concentrated on the electrode end 8 from the electrode support 7. Therefore, many electrons that migrate are collected at the electrode end 8. When an electron affinity impurity gas is contained in the detection gas 2, electrophoretic electrons are easily trapped and become negative ions. Then, the migration speed is reduced to about 1/1000, and apparently accumulates as a space charge layer around the electrode. This space charge layer becomes larger as the irradiation dose becomes larger, and the electric field in the vicinity of the electrode becomes smaller, facilitating the capture and recombination of electrophoretic electrons. Therefore, the amount of charge collected in the electrode support 7 has a better saturation characteristic than the amount of charge collected in the electrode end 8, and the linearity of the output current with respect to the irradiation dose is ensured even for a higher irradiation dose. The electric charge collected in the electrode support 7 is input to the ionization current measurement circuit 11 and the amount of current is measured. The charges collected at the electrode terminal 8 are input to the ionization current measuring circuit 11 through the current introduction terminal 9 and the amount of current is measured. Therefore, the ionization current value from the electrode support portion 7 has better saturation characteristics than the ionization current value from the electrode end portion 8, and the linearity of the output current with respect to the irradiation dose is ensured even for a higher irradiation dose.
[0021]
Thus, by measuring the signal from the gas ionization chamber 1 separately from the electrode support column 7 and the electrode end 8, it is possible to extract a portion with good dose linearity from the signal in the same detector, and to measure Can expand the dynamic range.
[0022]
Next, a second embodiment of the present invention will be described with reference to FIG. 2, the same parts as those in FIG. 1 are denoted by the same reference numerals, and detailed description thereof is omitted. In FIG. 2, the electrode support 7 is formed in a cylindrical shape, and the current introduction terminal 9 connected to the electrode end 8 is passed through the inside of the cylinder from the tip opening of the electrode support 7 while being electrically insulated from the electrode support 7. It is pulled out of the sex container 5.
[0023]
In the radiation detection apparatus according to the second embodiment of the present invention having such a configuration, there is no concentration of the electric field on the signal from the electrode end 8, so that the charge collection efficiency up to a higher dose in the electrode support 7. Does not decrease, the saturation characteristics are improved, the linearity with respect to the irradiation dose is extended to a high dose, and the linearity is improved.
[0024]
Next, a third embodiment of the present invention will be described with reference to FIG. 3, the same parts as those in FIG. 1 are denoted by the same reference numerals, and detailed description thereof is omitted. In FIG. 3, instead of the ionization current measurement circuit 11 shown in the first and second embodiments, a first ionization current measurement circuit 12 that measures the ionization current from the electrode support 7, and an electrode end 8 A second ionization current measurement circuit 13 for measuring the ionization current; an ionization current comparison circuit 14 for comparing the output of the first ionization current measurement circuit 12 and the output of the second ionization current measurement circuit 13; A signal switching correction circuit 15 connected to them is provided. In the signal switching correction circuit 15, whether the signal from the first ionization current measurement circuit 12, the signal from the second ionization current measurement circuit 13 is used as the output of the signal switching correction circuit 15, or the first A selection circuit for selecting whether to use the weighted and added outputs of the first ionization current measurement circuit 12 and the second ionization current measurement circuit 13 is included.
[0025]
In the radiation detection apparatus according to the third embodiment of the present invention having such a configuration, by comparing the outputs of the first ionization current measurement circuit 12 and the second ionization current measurement circuit 13, The degree of saturation of the current in part 8 is known. Using the information, the signal switching correction circuit 15 uses the signal from the first ionization current measurement circuit 12, the signal from the second ionization current measurement circuit 13, or the first ionization current measurement circuit 12. And whether the output of the second ionization current measuring circuit 13 is weighted and added is used. Thereby, the linearity can be maintained over a wide dynamic range of the ionization current signal output for one output as the radiation detection apparatus.
[0026]
Next, a fourth embodiment of the present invention will be described with reference to FIG. 4, the same parts as those in FIG. 3 are denoted by the same reference numerals, and detailed description thereof is omitted. FIG. 4 shows an example in which the ionization current comparison circuit 14 and the signal switching correction circuit 15 shown in FIG. 3 are provided for the electrode structure shown in FIG. 2, and the operational effects are the same as those of the third embodiment shown in FIG. The following effects can be obtained.
[0027]
Next, a fifth embodiment of the present invention will be described with reference to FIG. In FIG. 5, the radius of curvature of the electrode end 8 is made larger than the radius of the electrode support 7.
In the radiation detection apparatus according to the fifth embodiment of the present invention having such a configuration, the concentration of electrophoresed electrons on the electrode end portion 8 is alleviated, so that saturation characteristics during high-dose irradiation are improved, and Linearity can be maintained over a wide dynamic range.
[0028]
Next, a sixth embodiment of the present invention will be described with reference to FIG. In FIG. 6, the radius of curvature of the electrode end portion 8 is increased so that the electric field strength in the vicinity of the electrode surface is approximately the same at the electrode end portion 8 and the electrode post portion 7. The electrode end portion 8 is electrically connected to the electrode support portion 7 or formed as an integral part, and its output is connected to the ionization current measuring circuit.
[0029]
In the radiation detection apparatus according to the sixth embodiment of the present invention having such a configuration, the concentration of electrophoretic electrons on the electrode end portion 8 is alleviated, and the saturation characteristics during high-dose irradiation are improved. Only one system for the ionization current measurement circuit is required for each ionization chamber, resulting in a simplified measurement system.
[0030]
Next, a seventh embodiment of the present invention will be described with reference to FIG. 7, the same parts as those in FIG. 1 are denoted by the same reference numerals, and detailed description thereof is omitted. In FIG. 7, an electrode support 7 electrically insulated from the conductive container 5 in which the detection gas 2 is sealed is provided so as to penetrate the conductive container 5 in an airtight manner and protrude almost to the center of the conductive container 5. Yes. A round cap-shaped electrode terminal 8 is provided at the tip of the electrode support 7, and covers the tip of the electrode support 7 while being insulated from the electrode support 7. The electrode end portion 8 is electrically connected to the current introduction terminal 9 penetrating the conductive container 5 via the lead wire 10, and the electrode strut portion 7 and the electrode end portion 8 are respectively connected to the ionization current measuring circuit 11. Yes. The outer side of the electrode terminal part 8 is spherical, and the inner side has a structure in which a hole into which the cylindrical electrode support part 7 can be inserted is formed.
[0031]
In such a gas ionization chamber 1, a gas adsorbent 16 having an ability to adsorb oxygen molecules and nitrogen oxides is provided in the conductive container 5. The shape of the gas adsorbent 16 and the attachment position in the conductive container 5 are arbitrarily determined.
[0032]
In the radiation detection apparatus according to the seventh embodiment of the present invention having such a configuration, electrophoretic electrons are captured by impurities having a high electron affinity, such as oxygen molecules and nitrogen oxides contained in the detection gas 2. As a result, a space charge layer is formed. The electric charge generated in the conductive container 5 migrates along the lines of electric force applied between the conductive container 5 and the electrode support column 7 or the electrode end portion 8. On the other hand, the electric lines of force are concentrated on the electrode end 8 from the electrode support 7. Therefore, many electrons that migrate are collected at the electrode end 8. When an electron affinity impurity gas is contained in the detection gas 2, electrophoretic electrons are easily trapped and become negative ions. Then, the migration speed is reduced to about 1/1000, and apparently accumulates as a space charge layer around the electrode. This space charge layer becomes larger as the irradiation dose becomes larger, and the electric field in the vicinity of the electrode becomes smaller, facilitating the capture and recombination of electrophoretic electrons. Therefore, the amount of charge collected in the electrode support 7 has a better saturation characteristic than the amount of charge collected in the electrode end 8, and the linearity of the output current with respect to the irradiation dose is ensured even for a higher irradiation dose. The electric charge collected in the electrode support 7 is input to the ionization current measurement circuit 11 and the amount of current is measured. The charges collected at the electrode terminal 8 are input to the ionization current measuring circuit 11 through the current introduction terminal 9 and the amount of current is measured. Therefore, the ionization current value from the electrode support portion 7 has better saturation characteristics than the ionization current value from the electrode end portion 8, and the linearity of the output current with respect to the irradiation dose is ensured even for a higher irradiation dose.
[0033]
As described above, since the impurities in the detection gas 2 are reduced, the trapping of electrophoretic electrons is reduced, the saturation characteristic of the charge collection rate is improved, and the dynamic range with respect to the irradiation dose can be expanded.
[0034]
Next, an eighth embodiment of the present invention will be described with reference to FIG. 8, the same parts as those in FIG. 1 are denoted by the same reference numerals, and detailed description thereof is omitted. In FIG. 8, an electrode 7 a electrically insulated by an insulating lid 6 from a conductive container 5 filled with a detection gas 2 containing an inert gas as a main component penetrates the conductive container 5 in an airtight manner, and the conductive container 5. It is provided so as to protrude almost to the center. A transparent window 17 is airtightly provided in the conductive container 5, and a photodetector 18 is attached to the outside of the window 17. The material of the window 17 is a material that transmits the scintillation light of the detection gas 2. Such a wavelength converting substance 19 is applied. The output of the photodetector 18 is input to a general minute current measuring circuit or pulse counting circuit 20. Further, a signal from the electrode 7 a in the conductive container 5 is input to the ionization current measurement circuit 11. Further, the outputs of a general minute current measuring circuit or pulse counting circuit 20 and the ionizing current measuring circuit 11 are input to an output correction circuit 21 that corrects the output of the ionizing current measuring circuit 11 based on the signal of the light detection system.
[0035]
In the radiation detection apparatus according to the eighth embodiment of the present invention having such a configuration, the scintillation light of the detection gas 2 is ionized, or the molecules of the detection gas 2 to which energy has not been applied until ionization is performed. It is generated by the ions of the detection gas 2 recombined. Therefore, if electrophoresis is retained by the space charge layer in the vicinity of the electrode 7a, the probability that the accumulated electrons will recombine before reaching the electrode 7a increases. Although the conventional detector cannot measure the electrons that do not reach the electrodes, in the detection device according to the present invention, the recombined electrons can be detected by the photodetector 18 as scintillation light. Assuming that the ionization current measured by the electrode 7a is I, the output current from the photodetector 18 that measures the scintillation light is S, and the energy applied by radiation is E, the correction coefficient is α and the conversion coefficient β is used. , E = β (I + αS) has been experimentally shown, and the output correction circuit 21 can correct the saturation of charge collection by performing the same correction as E = β (I + αS). As a result, the recombination electrons contribute to the dose measurement, so that the saturation characteristic of the charge collection rate can be improved by correction, and the dynamic range with respect to the irradiation dose can be expanded.
[0036]
Next, a ninth embodiment of the present invention will be described with reference to FIG. 9, the same parts as those in FIG. 8 are denoted by the same reference numerals, and detailed description thereof is omitted. In FIG. 9, the output of the photodetector 18 is connected to a γ-ray identification / counting circuit 25 via a current measurement circuit 22, a pulse waveform discrimination circuit 23, and a pulse counting circuit 24. An electrode and an ionization current measuring circuit are not provided.
[0037]
In the radiation detection apparatus according to the ninth embodiment of the present invention having such a configuration, α-rays and cosmic rays are compared with those due to the interaction between secondary electrons caused by γ-rays and the detection gas 2. Due to the interaction with the detection gas 2, the pulse decay time of the scintillation light of the detection gas 2 is short. Therefore, the pulse waveform discrimination circuit 23 discriminates scintillation due to secondary electrons and scintillation due to α rays and cosmic rays. On the other hand, the pulse counting circuit 24 counts without distinguishing the type of radiation. Therefore, by supplying the γ-ray identification and counting circuit 25 with information on the radiation type and the count, the γ-ray identification and counting circuit 25 can count only gamma rays.
[0038]
Therefore, the radiation detection apparatus having such a configuration eliminates the influence of the background such as the α-ray background caused by the conductive container 5 by identifying only the signal by the γ-ray and performing the dose measurement. Low background measurement is possible.
[0039]
Next, a tenth embodiment of the present invention will be described with reference to FIG. 10, the same parts as those in FIG. 8 are denoted by the same reference numerals, and detailed description thereof is omitted. In FIG. 10, an electrode 7 a provided so as to penetrate the conductive container 5 in an airtight manner and protrude almost to the center of the conductive container 5 is connected to the ionization current measuring circuit 11, the pulse counting circuit 24, and the pulse charge amount measuring circuit 26. Is done. The output of the pulse charge amount measurement circuit 26 is input to the charge amount / current conversion circuit 27 together with the output of the pulse counting circuit 24. The output of the charge amount / current conversion circuit 27 is input to the output current correction circuit 28 together with the output of the ionization current measurement circuit 11, and the output of the charge amount / current conversion circuit 27 is subtracted from the output of the ionization current measurement circuit 11.
[0040]
With the radiation detection apparatus according to the tenth embodiment of the present invention having such a configuration, the generated charge amount of a signal having a relatively short pulse width, such as α rays, by the pulse counting described in the ninth embodiment. And the frequency of occurrence can be measured. Accordingly, the charge amount and the output of the current conversion circuit 27 are mainly a background current caused by α rays. Therefore, by subtracting the charge amount and the output of the current conversion circuit 27 from the output of the ionization current measurement circuit 11 in the output current correction circuit 28, the background current can be corrected, the α-ray background caused by the conductive container 5, etc. The measurement of low background can be performed without the influence of the background.
[0041]
Next, an eleventh embodiment of the present invention will be described with reference to FIG. 11, the same parts as those in FIG. 8 are denoted by the same reference numerals, and detailed description thereof is omitted. In FIG. 11, the output of the photodetector 18 is input to the γ-ray identification / counting circuit 25 via the current measurement circuit 22, the pulse waveform discrimination circuit 23, and the pulse counting circuit 24. The ionization current measurement circuit 11 is connected to an electrode 7 a provided so as to penetrate the conductive container 5 in an airtight manner and protrude almost to the center of the conductive container 5. Further, an ionization current measurement is performed using a current calculation circuit 29 that calculates the amount of charge generated by radiation other than γ-rays based on the signal from the photodetector 18, and the output of the current calculation circuit 29 and the output of the ionization current measurement circuit 11. An output correction circuit 30 for correcting the output of the circuit 11 is provided.
[0042]
In the radiation detection apparatus according to the eleventh embodiment of the present invention having such a configuration, a count value by radiation other than γ rays can be obtained by the γ ray identification described in the ninth embodiment. Based on this result, the current calculation circuit 29 calculates an average current value generated by the incidence of radiation other than γ rays. By inputting the obtained current value into the output correction circuit 30 and subtracting it from the output of the ionization current measurement circuit 11, the ionization current value due to the contribution of only the γ-ray can be obtained, and only the signal due to the γ-ray is identified. By performing the dose measurement, the influence of the background such as the α-ray background caused by the conductive container 5 can be eliminated, and the low background can be measured.
[0043]
【The invention's effect】
As described above, according to the present invention, the conductive container in which the detection gas is sealed, and the electrode supporting column provided in the conductive container through the conductive container while being electrically insulated from the conductive container. And an electrode end portion that covers the tip end portion of the electrode column portion while being insulated from the electrode column portion, and an ionization current measuring circuit connected to the electrode column portion and the electrode end portion. So the measurement dynamic range is wide A radiation detection apparatus can be provided.
[Brief description of the drawings]
FIG. 1 is a block configuration diagram showing a radiation detection apparatus according to a first embodiment of the present invention.
FIG. 2 is a block configuration diagram showing a radiation detection apparatus according to a second embodiment of the present invention.
FIG. 3 is a block diagram showing a radiation detection apparatus according to a third embodiment of the present invention.
FIG. 4 is a block diagram showing a radiation detection apparatus according to a fourth embodiment of the present invention.
FIG. 5 is a block configuration diagram showing a radiation detection apparatus according to a fifth embodiment of the present invention.
FIG. 6 is a block configuration diagram showing a radiation detection apparatus according to a sixth embodiment of the present invention.
FIG. 7 is a block diagram showing a radiation detection apparatus according to a seventh embodiment of the present invention.
FIG. 8 is a block diagram showing a radiation detection apparatus according to an eighth embodiment of the present invention.
FIG. 9 is a block diagram showing a radiation detection apparatus according to a ninth embodiment of the present invention.
FIG. 10 is a block diagram showing a radiation detection apparatus according to a tenth embodiment of the present invention.
FIG. 11 is a block diagram showing a radiation detection apparatus according to an eleventh embodiment of the present invention.
FIG. 12 is a block diagram showing a conventional radiation detection apparatus.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Gas ionization chamber, 2 ... Detection gas, 5 ... Conductive container, 7 ... Electrode support | pillar part, 7a ... Electrode, 8 ... Electrode terminal part, 9 ... Current introduction terminal, 11 ... Ionization current measurement circuit, 12 ... 1st Ionization current measurement circuit, 13 ... second ionization current measurement circuit, 14 ... ionization current comparison circuit, 15 ... signal switching correction circuit, 16 ... gas adsorbent, 17 ... window, 18 ... photodetector, 19 ... wavelength conversion Substance: 20 ... Minute current measuring circuit or pulse counting circuit, 21 ... Output correction circuit, 22 ... Current measuring circuit, 23 ... Pulse waveform discrimination circuit, 24 ... Pulse counting circuit, 25 ... Gamma ray identification counting circuit, 26 ... Pulse charge Quantity measuring circuit, 27... Charge amount, current conversion circuit, 28... Output current correction circuit, 29... Current calculation circuit, 30.

Claims

And encapsulating detected gas conducting container, electrically insulated with the conductive container through the gas-tight electrically conductive electrode struts provided in the container from the conductive container, said electrode support portion an electrode distal end positioned at the distal end covers the distal end of the electrode support portion while being insulated from the electrode support portion, the radiation detecting device comprising the said electrode support portion and the electrode terminal portion and the connected ionization current measuring circuit .

And encapsulating detected gas conducting container, electrically insulated with the conductive container through the gas-tight electrically conductive cylindrical electrode post portion provided in the container from the conductive container, said electrodes an electrode terminal portion which covers the tip of the electrode support portion while being insulated from and positioned at the front end of the column portion the electrode support portion, the through electrode struts in the cylinder is connected to the electrode terminal portion electrically the a current introducing terminal penetrating the conductive container, the radiation detecting device comprising the said electrode support portion and the electrode terminal portion and the connected ionization current measuring circuit.

And encapsulating detected gas conducting container, electrically insulated with the conductive container through the gas-tight electrically conductive electrode struts provided in the container from the conductive container, said electrode support portion an electrode distal end positioned at the distal end covers the distal end of the electrode support portion while being insulated from the electrode support portion, and the first ionization current measuring circuit connected to the electrode support portion is connected to the electrode terminal portions The second ionization current measurement circuit, the output from the first ionization current measurement circuit, and the second ionization current connected to the first ionization current measurement circuit and the second ionization current measurement circuit, respectively. A radiation detector comprising: an ionization current comparison circuit for comparing an output from a measurement circuit; and a signal switching correction circuit connected to the first ionization current measurement circuit and the second ionization current measurement circuit. The signal switching correction circuit Whether to use the output from the first ionization current measurement circuit or the output from the second ionization current measurement circuit based on the information from the ionization current comparison circuit, or to use the output from the second ionization current measurement circuit And a selection circuit for selecting whether to use a weighted output of the output from the second ionization current measuring circuit .

And encapsulating detected gas conducting container, electrically insulated with the conductive container through the gas-tight electrically conductive cylindrical electrode post portion provided in the container from the conductive container, said electrodes an electrode terminal portion which covers the tip of the electrode support portion while being insulated from and positioned at the front end of the column portion the electrode support portion, the through electrode struts in the cylinder is connected to the electrode terminal portion electrically the A current introduction terminal penetrating the conductive container; a first ionization current measurement circuit connected to the electrode post; a second ionization current measurement circuit connected to the electrode end; and the first ionization. An ionization current comparison circuit connected to each of the current measurement circuit and the second ionization current measurement circuit and comparing the output from the first ionization current measurement circuit and the output from the second ionization current measurement circuit ; Before the first ionization current measurement circuit A signal switching correction circuit connected to the second ionization current measuring circuit, a radiation detector consisting of the signal switching correction circuit, the first ionization current based on information from said ionization current comparator circuit Whether to use the output from the measurement circuit, to use the output from the second ionization current measurement circuit, or to weight the output from the first ionization current measurement circuit and the output from the second ionization current measurement circuit And a selection circuit for selecting whether to use the added one .

The electrode distal end is rounded cap shape, the electrode strut is a cylindrical shape, according to claim 1, wherein the electrode terminal portion and having a large kina radius of curvature than the electrode strut The radiation detection apparatus in any one of thru | or 4.