JP3565973B2 - Radiation counting device - Google Patents

Description

【００１０】
一方、「非まひ型」について図１０に従って説明する。
【００１１】
有効な入力パルスの波高値をＡＤ変換等に要する時間中に入力した次のパルスを無効とする場合、不感時間はＡＤ変換等の所要時間であるが、無効となった第２のパルスはＡＤ変換されないため、新たな不感時間が発生せず、回路はまひしない。この場合、次の式（２）が成立する。
【００１２】
ｎ＝ｍ／（１−ｍτ）−−−−（２）
【００１３】
上記「まひ型」および「非まひ型」のいずれの場合もｍ／ｎ＝実効測定時間／実時間となる。
【００１４】
計数記憶器６は、波高弁別器５で区切られた波高範囲の一部または全ての範囲、すなわち、チャンネル毎に整数型の記憶器を具備し、主増幅器４および波高弁別器５のいずれにも有効と判断されたパルスが波高弁別器５により弁別された波高範囲のチャンネルの記憶器の記憶値に１を加算または記憶値から１を減算する。また、計数記憶器６は測定時間計数用の記憶器を別途具備し、測定開始からの経過時間を実時間および実効測定時間のいずれかまたは両方について計数する。計数記憶器６の記憶値は、計算機９に読込まれ、例えば、放射線検出信号の各チャンネルの計数値を実効測定時間の計数値で除することにより、各チャンネルにおける計数率を算出するなどのデータ処理や解析が行われる。
【００１５】
【発明が解決しようとする課題】
しかし上記した放射線計数装置１では、次に説明するように正しい放射線の数が計数できないという問題がある。
【００１６】
まず、第一に、前述のように、従来の技術は実効測定時間内において検出された放射線の数を計数するものであり、計数値を実効測定時間で除して得られる計数率は、実効測定時間について平均計数率となる。従って、測定中に計数率の変化があり、放射線検出の時間間隔の期待値が変化し、それにより各時刻の近辺における短時間中の実効測定時間と実時間の比率が一定でなくなった場合、計数率は実時間についての平均と実効測定時間についての平均が異なった値となり、正確な実時間についての平均を得ることは難しい。
【００１７】
例えば、図８に示す放射線計数装置１による場合に、例えば、τ＝５０μｓｅｃの「まひ型」の不感時間があり、１０００秒間（実時間）の測定する場合を考える。
【００１８】
前半の５００秒間の真の計数率が１ｋｃｐｓ（毎秒１０００パルス）で、後半の５００秒間の真の計数率が１０ｋｃｐｓ（毎秒１００００パルス）であったとする。１０００秒間における真の平均計数率は、次の式（３）で示される。
【００１９】
（１ｋｃｐｓ×５００ｓｅｃ＋１０ｋｃｐｓ×５００ｓｅｃ）／１０００ｓｅｃ＝５．５ｋｃｐｓ−−−−（３）
【００２０】
ところが、実測によると、前半５００秒における実測計数値は、次の式（４）で示される。
【００２１】
【数２】

【００２２】
また、実効測定時間は、次の式（５）で示される。
【００２３】
【数３】

【００２４】
後半５００秒における実測計数値は、次の式（６）で示される。
【００２５】
【数４】

【００２６】
また、実効測定時間は、次の式（７）で示される。
【００２７】
【数５】

【００２８】
従って、１０００秒間では、計数値の合計は、次の式（８）で示される。
【００２９】

さらに、実効測定時間の合計は、次の式（９）で示される。
全実効測定時間＝４７６＋３０３＝７７９（ｓｅｃ）−−−−（９）
従って、平均計数率は、次の式（１０）で示される。
平均計数率＝３５０８２６８／７７９＝約４５０４＝４．５ｋｃｐｓ−−−−（１０）
【００３０】
上記式（１０）で得られる平均計数率４．５ｋｃｐｓは式（３）で得られる真の計数率５．５ｋｃｐｓと一致しない。
【００３１】
ここで、前半５００秒について考察すると（実時間／実効測定時間）×計数値の式（１１）が得られる。
（５００／４７６）×４７５６１５＝約５０００００−−−−（１１）
また、後半５００秒について考察すると（実時間／実効測定時間）×計数値の式（１２）が得られる。
（５００／３０３）×３０３２６５３＝約５００００００−−−−（１２）
この値の合計値を全測定時間（実時間）で割ると次の式（１３）が得られる。
（５０００００＋５００００００）／１０００＝５５００＝５．５ｋｃｐｓ−−−−（１３）
【００３２】
従って、真の計数率と一致する。上記例では、各５００秒の期間の中で計数率変化は無いと仮定したためであり、実効測定時間が変化すれば正しい計数率をえることは難しい。
【００３３】
また、第二に、測定対象物を相対的に走査しながら測定する場合、測定時間内に走査速度の変化があると測定対象物の各位置毎の測定時間が一定でなくなり、計数率の時間積分値である計数値から求めた平均計数率からは、計数率の位置平均が得られない。
【００３４】
すなわち、例えば、計数率が濃度に比例する場合において、流量と濃度と計数との関係を考える。
【００３５】
まず、前半５００秒では、１ｌ／ｓｅｃ（流量）、１００ｇ／ｌ（濃度）、１００ｃｐｓ（計数）が得られ、続いて、後半５００秒では、２ｌ／ｓｅｃ（流量）、２００ｇ／ｌ（濃度）、２００ｃｐｓ（計数）が得られるとする。この場合、１０００秒平均は１．５ｌ／ｓｅｃ（流量）、１５０ｇ／ｌ（濃度）、１５０ｃｐｓ（計数）となり、次の式（１４）と式（１５）が得られる。
【００３６】
真の全溶質量＝（５００×１×１００＋５００×２×２００）＝２５０００（ｇ）−−−−（１４）
平均計数率による全溶質量＝１０００×１．５×１５０＝２２５０００（ｇ）−−−−（１５）
【００３７】
このように、式（１４）による真の全溶質量と式（１５）による平均計数率による全溶質量とは一致しない。
【００３８】
さらに、第三に、求めようとする量と計数率とが線形関係でない場合、例えば、吸収濃度計のように求めようとする物質濃度が計数率の対数の関数となる場合に、計数率の時間積分値と求めようとする物質の時間積分値が比例しないことから明らかなように、計数率の時間積分値である計数値から求めた平均計数率からは、求めようとする量の時間平均が得られない。例えば、レントゲン写真のように放射線の透過で、物質の密度（濃度）等を計る場合、計数率Ｒは、密度（濃度）ρと試料厚さｔとにより次の式（１６）が得られる。
【００３９】
【数６】

【００４０】
上記の場合、次の式（１７）と式（１８）と式（１９）と式（２０）が得られる。
【００４１】
平均は、（１００×５００＋２００×５００）／１０００＝１５０−−−−（１７）
【００４２】
【数７】

【００４３】
１０００秒間の平均計数率は、
（３０３２６５３＋１８３９３９７）／１０００＝約４８７２＝４．８７ｋｃｐｓ−−−−（２０）
【００４４】
上記式（１８）と式（１９）、式（２０）によりρを逆算すると次の式（２１）が得られる。
【００４５】
【数８】

このように平均と一致しない。
【００４６】
そこで、本発明は、測定時間内に計数率や測定対象物の走査速度などが変化しても、求めようとする量の時間平均や位置平均などを正しく測定できる放射線計数装置を提供することを目的とする。
【００４７】
【課題を解決するための手段】
請求項１の発明は、放射線源より放射された放射線を放射線検出器によって検出して電気信号に変換すると共に、放射線のエネルギーに比例した波高パルス信号としての有効な放射線検出信号を計数記憶する放射線計数装置において、有効な放射線検出信号が入力される毎に、その間の放射線検出時間に基づく情報を用いて予め決められた手順によって有効な放射線検出信号の加算値を決定する第１加算値決定手段と、この第１加算値決定手段により得られる加算値を積算して有効な放射線検出信号の計数値を記憶する第１計数値記憶手段と、有効な放射線検出信号が入力される毎に、その間の放射線検出時間に基づく情報を用いて予め決められた手順によって統計誤差値を得るための加算値を決定する第２加算値決定手段と、この第２加算値決定手段により得られる加算値を積算して第１計数値記憶手段により得られる計数値を評価する統計誤差値を記憶する第２計数値記憶手段を具備するようにしたものである。以上の手段によって、有効な放射線検出信号が入力される毎にその間の放射線検出に基づく情報を用いて加算値を決定し積算される。この結果、測定時間中に放射線検出に基づく情報の変化があっても、有効な放射線検出信号の入力毎である最小期間毎に加算値を決定するから計数値に与える影響が最小限に抑えられ正確な計数率を得ることができる。さらに、統計誤差値が最小期間毎に加算値として積算され、得られる全体の統計誤差値も正確なものが得られる。従って、得られる計数率に対して正しい評価をすることができる。
【００５０】
請求項２の発明は、放射線源と放射線検出器との間に測定対象物である移動物質を配置して放射線源から移動物質を透過して来た放射線を放射線検出器により検出して電気信号に変換すると共に、放射線のエネルギーに比例した波高パルス信号として有効な放射線検出信号を計数して記憶する放射線計数装置において、有効な放射線検出信号を入力する毎に当該有効な放射線検出信号とその一つ前の有効な放射線検出信号との間の実効測定時間の対数値と実時間の積を加算値と決定する加算値決定手段と、この加算値決定手段により得られる加算値を積算する計数値記憶手段とを具備するようにしたものである。以上の手段によって、有効な放射線検出信号毎である最小期間毎に実時間と実効測定時間の対数値との積が加算値として決定され順次積算される。この結果、実効測定時間や物質の濃度等に変化があっても最小期間毎に加算され、しかも、線形な量を計数するから計数値に与える誤差が最小値とされる。従って、移動物質の速度が一定の場合、得られた計数値に基づいて移動物質の実時間平均が正確に得られる。
【００５１】
請求項３の発明は、測定対象物である放射線放出物を含む移動物質からの放射線を放射線検出器により検出して電気信号に変換すると共に、放射線のエネルギーに比例した波高パルス信号として有効な放射線検出信号を計数して記憶する放射線計数装置において、有効な放射線検出信号を入力する毎に当該有効な放射線検出信号とその一つ前の有効な放射線検出信号との間の実時間を実効測定時間によって除算した値と移動物質の速度との積を加算値と決定する加算値決定手段と、この加算値決定手段により得られる加算値を積算する計数値記憶手段とを具備するようにしたものである。以上の手段によって、有効な放射線検出信号毎である最小期間毎に実時間と実効測定時間との比率と移動物質の速度との積が加算値として決定され順次積算される。この結果、実効測定時間に変化があっても最小期間毎に加算されるために、実効測定時間が、計数値に与える誤差が最小値とされる。従って、得られた計数値に基づいて移動物質の位置平均を正確に得ることができる。
【００５２】
【発明の実施の形態】
図１は、本発明の第１実施の形態を示す放射線計数装置の構成図である。
【００５３】
図１において、従来例を示す図８と同一符号は、同一部分または相当部分を示し、図１について図８と異なる主な点は、計数記憶器６と計算機９に代えて、加算値決定手段１０と計数値記憶手段１１とを設けたことである。
【００５４】
ここで、加算値決定手段１０は、波高弁別器５から放射線検出信号が入力される毎に、放射線検出時間と共に変化する情報を用いて、予め決められた手順により積算すべき加算値を決定するものである。計数値記憶手段１１は、加算値決定手段１０により得られた加算値を積算する機能を有するものである。
【００５５】
以上の構成によれば、加算値決定手段１０へ放射線検出信号が入力される毎に、例えば、実効測定時間と実時間の比率や、放射線検出器２が測定対象物を走査する速度などの時間と共に変化する情報を用いて、測定目的に応じて予め決められた手順により加算値を決定し、計数値記憶手段１１により加算値を積算し記憶する。従って、可能な限り小さい最小区間によって得られる情報を用いて加算値を決定するから積算値として得られる値は、正確であり、計数率の実効測定時間についての積分値ではなく、測定目的に応じたもの、例えば、計数率の実時間平均を得ることが測定目的であるならば計数率の実時間積分とすることができる。
【００５６】
なお、第１実施の形態に対して第２の実施の形態として、加算値決定手段１０および計数値記憶手段１１が、加算値および積算値を浮動小数点方式の実数として取扱う構成としてもよい。
【００５７】
この構成によれば、加算値決定手段１０に放射線検出信号が入力される毎に、時間と共に変化する他の情報を用いて、測定目的に応じた加算値を浮動小数点方式の実数として決定し、計数値記憶手段１１により加算値を浮動小数点方式の実数として積算し記憶する。従って、測定目的から加算値や積算値を実数とする必要がある場合でも、計数値記憶手段１１に記憶された積算値から、測定目的を達成できる。
【００５８】
なお、第１実施の形態に対して第３の実施の形態として、図１に示した例において、加算値決定手段１０における加算値決定手順が、積算することにより実時間について平均計数率が得られるところの値としてもよい。
【００５９】
この構成によれば、加算値決定手段１０に放射線検出信号が入力される毎に、時間と共に変化する他の情報を用いて、実時間についての平均計数率を求めることを目的とした加算値を決定し、計数値記憶手段１１により加算値を積算し記憶する。従って、計数値記憶手段１１に記憶された積算値から、実時間についての平均計数率が正しく得られる。
【００６０】
なお、第１実施の形態に対して第４の実施の形態として、図１に示した例において、加算値決定手段１０における加算値決定手順が、時刻を含む短時間内の実効測定時間に対する実時間の比率を加算値とするものであることを加えるようにしてもよい。
【００６１】
この構成によれば、加算値決定手段１０に放射線検出信号が入力される毎に、時刻を含む短時間内における実効測定時間に対する実時間の比率を加算値として決定し、計数値記憶手段１１により加算値を積算し記憶する。従って、放射線検出信号が無効となることによる放射線検出数の補償が行われ、計数値記憶手段１１に記憶された積算値を全実時間で除することにより、実時間についての平均計数率が得られる。
【００６２】
なお、第１実施の形態に対して第５の実施の形態として図１に示した例において、加算値決定手段１０における加算値決定手順が、放射線検出信号とそれ以前の最後の有効な放射線検出信号の時間間隔を実効測定時間について実測した実効測定時間間隔実測値に対する放射線検出信号とそれ以前の最後の有効な放射線検出信号の時間間隔を実時間について実測した実測時間間隔実測値の比率を加算値とするものでもよい。
【００６３】
この構成によれば、加算値決定手段１０に放射線検出信号が入力される毎に、放射線検出信号とそれ以前の最後の有効な放射線検出信号の時間間隔を実効測定時間と実時間についてそれぞれ実測し、実効測定時間間隔実測値に対する実時間間隔実測値の比率を加算値として決定し、計数値記憶手段１１により加算値を積算し記憶する。従って、実効測定時間間隔の逆数、すなわち、計数率の実時間での積分が得られ、計数値記憶手段１１に記憶された積算値を全実時間で除することにより、実時間についての平均計数率が得られる。
【００６４】
なお、第１実施の形態に対して第６の実施の形態として図１に示した例において、加算値決定手段１０における加算値決定手順が、積算することにより、測定対象物の位置についての平均計数率が得られるところの値を加算値するものでもよい。
【００６５】
この構成によれば、加算値決定手段１０に放射線検出信号が入力される毎に、時間と共に変化する他の情報を用いて、測定対象物の位置について平均計数率を求めることを目的とした加算値を決定し、計数値記憶手段１１により加算値を積算し記憶する。従って、計数値記憶手段１１に記憶された積算値から、測定対象物の位置について平均計数率が正しく得られる。
【００６６】
なお、第１実施の形態に対して第７の実施の形態として図１に示した例において、加算値決定手段１０における加算値決定手順が、時刻を含む短時間内の実効測定時間に対する実時間の比率と図示しない測定対象物と放射線検出器の相対的移動速度の積を加算値とするものでもよい。
【００６７】
この構成によれば、加算値決定手段１０に放射線検出信号が入力される毎に、時刻を含む短時間内の実効測定時間に対する実時間の比率と測定対象物と放射線検出器の相対的移動速度の積を加算値として決定し、計数値記憶手段１１により加算値を積算し記憶する。従って、放射線検出信号が無効となることによる放射線検出数の補償と測定対象物各位置における測定時間の違いの補償が同時に行われ、計数値記憶手段１１に記憶された積算値を測定対象物と放射線検出器の相対的全移動距離で除することにより、位置についての平均計数率が得られる。
【００６８】
なお、第１実施の形態に対して第８の実施の形態として図１に示した例において、加算値決定手段１０における加算値決定手順が、放射線検出信号とそれ以前の最後の有効な放射線検出信号の時間間隔を実効測定時間について実測した実効測定時間間隔実測値に対する放射線検出信号とそれ以前の最後の有効な放射線検出信号の時間間隔を実時間について実測した実測時間間隔実測値の比率と図示しない測定対象物と放射線検出器の相対的移動速度を加算値とするものでもよい。
【００６９】
この構成によれば、加算値決定手段１０に放射線検出信号が入力される毎に、放射線検出信号とそれ以前の最後の有効な放射線検出信号の時間間隔を実効測定時間と実時間についてそれぞれ実測し、実効測定時間間隔実測値に対する実時間間隔実測値の比率と、測定対象物と放射線検出器の相対的移動速度の積を加算値として決定し、計数値記憶手段１１により加算値を積算し記憶する。従って、実効測定時間間隔の逆数、すなわち、計数率の移動距離での積分が得られ、計数値記憶手段１１に記憶された積算値を測定対象物と放射線検出器の相対的全移動距離で除することにより、位置についての平均計数率が得られる。
【００７０】
なお、第１実施の形態に対して第９の実施の形態として図１に示した例において、加算値決定手段１０における加算値決定手順が、積算することにより、放射線が透過してきた物質の量の時間平均が得られるところの値を加算値とするものでもよい。
【００７１】
この構成によれば、加算値決定手段１０に放射線検出信号が入力される毎に、時間と共に変化する他の情報を用いて、放射線が透過する物質の量の実時間についての平均を求めることを目的とした加算値を決定し、計数値記憶手段１１により加算値を積算し記憶する。従って、計数値記憶手段１１に記憶された積算値から放射線が透過する物質の量の実時間について平均が正しく得られる。
【００７２】
なお、第１実施の形態に対して第１０の実施の形態として図１に示した例において、加算値決定手段１０における加算値決定手順が、放射線検出信号とそれ以前の同じチャンネルの最後の有効な放射線検出信号の時間間隔を実効測定時間について実測した実効測定時間間隔実測値の対数値と放射線検出信号とそれ以前の同じチャンネルの最後の有効な放射線検出信号の時間間隔を実時間について実測した実時間間隔実測値の積を加算値とするものでもよい。
【００７３】
この構成によれば、加算値決定手段１０に放射線検出信号が入力される毎に、放射線検出信号とそれ以前の同じチャンネルの最後の有効な放射線検出信号の時間間隔を実効測定時間と実時間についてそれぞれ実測し、実効測定時間実測値の対数値と実時間実測値の積を加算値として決定し、計数値記憶手段１１により加算値を積算し記憶する。物質の量は、それを透過した放射線の強度の対数と線形な関係であり、放射線計数率の対数値を実時間で積分し、全実時間で除した値から、物質量の時間平均が得られる。放射線検出信号の実効測定時間での間隔の逆数は、その時間での計数率であり、実効測定時間間隔の対数値に実時間間隔を乗じた値の積算値は、物質の量の時間平均の符号を反転した値に比例する。従って、計数値記憶手段１１に記憶された積算値の符号を反転し、全実時間で除した値から、放射線が透過する物質の量の実時間についての平均が正しく得られる。
【００７４】
なお、第１実施の形態に対して第１１の実施の形態として図１に示した例において、加算値決定手段１０における加算値決定手順が、積算することにより、放射線が透過してきた物質の量の測定対象物の位置について平均が得られるところの値を加算値とするものでもよい。
【００７５】
この構成によれば、加算値決定手段１０に放射線検出信号が入力される毎に、時間と共に変化する他の情報を用いて、放射線が透過する物質の量の測定対象物の位置についての平均を求めることを目的とした加算値を決定し、計数値記憶手段１１により加算値を積算し記憶する。従って、計数値記憶手段１１に記憶された積算値から放射線が透過する物質の量の位置について平均が容易に得られる。
【００７６】
なお、第１実施の形態に対して第１２の実施の形態として図１に示した例において、加算値決定手段１０における加算値決定手順が、放射線検出信号とそれ以前の同じチャンネルの最後の有効な放射線検出信号の時間間隔を実効測定時間について実測した実効測定時間間隔実測値の対数値と放射線検出信号とそれ以前の同じチャンネルの最後の有効な放射線検出信号の時間間隔を実時間について実測した実時間間隔実測値と図示しない測定対象物と放射線検出器の相対的移動速度の積を加算値とするものでもよい。
【００７７】
この構成によれば、加算値決定手段１０に放射線検出信号が入力される毎に、放射線検出信号とそれ以前の同じチャンネルの最後の有効な放射線検出信号の時間間隔を実効測定時間と実時間についてそれぞれ実測し、実効測定時間実測値の対数値と実時間実測値と測定対象物と放射線検出器の相対的移動速度の積を加算値として決定し、計数値記憶手段１１により加算値を積算し記憶する。物質の量は、それを透過した放射線の強度の対数と線形な関係であり、放射線計数率の対数値を測定対象物と放射線検出器の相対的位置で積分し、全移動距離で除した値から、物質量の位置平均が得られる。放射線検出信号の実効測定時間での間隔の逆数は、その時間での計数率であり、実効測定時間間隔の対数値にその時間間隔での移動距離、すなわち、実時間間隔と移動速度を乗じた値の積算値は、物質の量の位置平均の符号を反転した値に比例する。従って、計数値記憶手段１１に記憶された積算値の符号を反転し、測定対象物と放射線検出器の相対的全移動距離で除した値から、放射線が透過する物質の量の位置についての平均が正しく得られる。
【００７８】
次に、図２は、本発明の第１３実施の形態を示す放射線計数装置の構成図である。
【００７９】
図２において、従来例を示す図８と同一符号は、同一部分または相当部分を示し、図２について図８と異なる主な点は、計数記憶器６と計算機９に代えて複数の加算値決定手段１０ａ，１０ｂと複数の計数値記憶手段１１ａ，１１ｂとを設けたことである。
【００８０】
ここで、加算値決定手段１０ａ，１０ｂは、放射線検出信号が入力される毎に放射線検出時間と共に変化する情報を用いて予め決められた手順により積算すべき値を決定するものである。計数値記憶手段１１ａ，１１ｂは、加算値決定手段１０ａ，１０ｂにより得られた加算値を積算するものである。
【００８１】
以上の構成によれば、複数の加算値決定手段１０ａ，１０ｂに放射線検出信号が入力される毎に、放射線検出時間と共に変化する情報を用いて、例えば、放射性物質量の測定と放射線吸収物質量の測定などのように、複数の測定目的毎にそれぞれに応じた複数の加算値を決定し、複数の計数値記憶手段１１ａ，１１ｂにより測定目的毎に加算値を積算し記憶する。従って、複数の加算値決定手段１０ａ，１０ｂに記憶された複数の積算値から、同時に複数の測定目的を達成できる。
【００８２】
なお、第１３実施の形態に対して第１４実施の形態として、図２に示した例において、一つの加算値決定手段１０ａにおける加算値決定手順が積算することにより、他の加算値決定手段１０ｂにより決定される加算値の積算値の偶発誤差の分散が得られるところの値を加算値とするものでもよい。
【００８３】
この構成によれば、複数の加算値決定手段１０ａ，１０ｂに放射線検出信号が入力される毎に、放射線検出時間と共に変化する情報を用いて、少なくとも一つの測定目的に応じた加算値と、その加算値の積算値の偶発誤差の範囲の評価を目的とした加算値を決定し、複数の計数値記憶手段１１ａ，１１ｂによりそれぞれの独立に加算値を積算し記憶する。従って、複数の計数値記憶手段１１ａ，１１ｂに記憶された複数の積算値から、少なくとも一つの測定目的が達成されると同時に、その測定目的の偶発誤差評価が容易に達成できる。
【００８４】
例えば、計数統計の揺らぎによる偶発誤差の分散は、加算値が常に１の場合は従来技術による計数の場合と同様に積算値そのものになるが、そうでない場合は一つの加算値の計数統計の揺らぎによる偶発誤差の分散の積算を別途行うことで、前述の計数統計揺らぎによる偶発誤差の分散が得られる。
【００８５】
例えば、次の式（２２）から計数統計誤差値が得られる。
【００８６】
【数９】

【００８７】
ここで、Ｆ’（ｉ）：ある有効な放射線検出信号とその一つ前の有力な放射線検出信号との間の加算値の関数の微分値
ｎ：有効な放射線検出信号の区間数
ｉ：ある有効な放射線検出信号の区間の信号パルス
【００８８】
なお、第１３実施の形態に対して第１５実施の形態として、図２に示した例において、一つの加算値決定手段１０ａにおける加算値決定手順が、他の加算値決定手段１０ｂにより決定された加算値の２乗を項として含んだ値を加算値とするものでもよい。
【００８９】
この構成によれば、複数の加算値決定手段１０ａ，１０ｂのうちの少なくとも一つにより放射線検出信号が入力される毎に、放射線検出時間と共に変化する情報を用いて、測定目的に応じた加算値を決定し、一つの計数値記憶手段１１によって加算値を積算し記憶する。
【００９０】
また、他の加算値決定手段１０により前記測定目的に応じた加算値の２乗を加算値として決定し、他の計数値記憶手段１１により後者の加算値を積算し記憶する。測定目的に応じた加算値の２乗の積算値の平方根は、次の式（２３）に示す如く、計数統計誤差による測定目的に応じた加算値の偶発誤差σに相当する。
【００９１】
【数１０】

【００９２】
上記のように、前者の計数値記憶手段１１に記憶された積算値から、少なくとも一つの測定目的が達成されると同時に後者の計数値記憶手段１１に記憶された積算値から前記測定目的の偶発誤差評価が容易に達成できる。
【００９３】
次に、図３に示す第１６実施の形態について説明する。
【００９４】
第１６実施の形態は、第１実施の形態乃至第５実施の形態、第１３実施の形態乃至第１５実施の形態を具体的に本発明に適用したものである。
【００９５】
ここで、放射線計数装置１Ｃには、放射性物質が含まれている測定対象物１２と測定対象物を一定速度で回転させるモータ１３と測定対象物内の放射性物質より発生する放射線８を絞るコリメータ１４および放射線計数装置１のデータ処理用の計算機９が接続されている。
【００９６】
また、放射線計数装置１は、測定対象物１２に対してコリメータ１４を介した位置に配置された放射線検出器２と前置増幅器３と主増幅器４と波高弁別器５と放射線検出信号が入力される毎に放射線検出信号とそれ以前の最後の有効な放射線検出信号の実効測定時間間隔に対する実時間間隔の比率を加算値として決定する機能を有する加算値決定手段１０ａと放射線検出信号が入力される毎に放射線検出信号とそれ以前の最後の有効な放射線検出信号の実効測定時間間隔に対する実時間間隔の比率の２乗を加算値として決定する機能を有する加算値決定手段１０ｂと計数値記憶手段１１ａおよび計数値記憶手段１１ｂにより構成される。
【００９７】
なお、加算値決定手段１０ａ，１０ｂと計数値記憶手段１１ａ，１１ｂは、加算値および積算値を浮動小数点方式の実数として扱うようにしている。
【００９８】
以上の構成で、モータ１３により一定速度で回転する測定対象物１２のうち、コリメータ１４によって絞られた範囲内の放射性物質から発生した放射線８が入射する。これにより、波高弁別器５より弁別された波高範囲の値と共に放射線検出信号が加算値決定手段１０ａ，１０ｂに入力される。
【００９９】
加算値決定手段１０ａでは、図４および図５に示すように、放射線検出信号が入力される毎に放射線検出信号とそれ以前の有効な放射線検出信号の実効測定時間間隔に対する実時間間隔の比率を加算値ａとして決定し、計数値記憶手段１１ａの前記波高範囲に割当てられた記憶器にて加算値ａを積算し記憶する。
【０１００】
具体的な説明をすると、図４は、放射線検出信号が放射線検出器２へ入力した際の各機器の作用を示し、放射線検出器２では、放射線検出信号が入力したとき瞬時だけパルス状の信号が出力され、前置増幅器３では、ＣＲ回路による図示する波形に変換され、主増幅器４へ出力される。そして、主増幅器４により図示する山状の波形として増幅される。この場合に図示左側のように主増幅器４から山状の波形が重なって波高弁別器５へ入力すると波高弁別器５では、まひ型不感時間のとき、図示上段のように、重なった短形波を出力する一方、非まひ型不感時間のときＡ−Ｄ変換を開始するが、パイルアップを検知して図示するように中断してしまう。
【０１０１】
これに対応して、計数値記憶手段１１ａでは、実効測定時間のクロックをＲＵＮ→ＳＴＯＰとしてクロックのカウントを停止する。この結果、この間について実効測定時間の加算が除外される。
【０１０２】
図示最下段のように、時刻ｔ１に一つ前の有効な放射線検出信号が入力し、その後の時刻ｔ２に当該有効な放射線検出信号が入力すると、実時間および実効測定時間は、次の式（２４），式（２５）で示される。
【０１０３】
実時間＝時刻ｔ２−時刻ｔ１−−−−（２４）
実効測定時間＝実時間−｛（時刻ｔｃ−時刻ｔａ）−−−−｝ −−（２５）
【０１０４】
さらに、本発明の実施の形態では、上記時刻ｔ２−時刻ｔ１の区間で、次の計数のための加算値と計数統計誤差のためのそれぞれの加算値を決定する。まず、加算値決定手段１０ａでは、次の式（２６）について加算値を区間毎に決定する。
【０１０５】
加算値＝（実時間／実効測定時間）−−−−（２６）
【０１０６】
また、加算値決定手段１０ｂでは、次の式（２７）について加算値を区間毎に決定する。
【０１０７】
加算値＝（実時間／実効測定時間）の二乗−−−−（２７）
【０１０８】
さらに、具体的に説明すると、図５に示すように第１の有効な放射線検出信号（図示第１有効パルス）から第ｎの有効な放射線検出信号（図示第ｎ有効パルス）が主増幅器４へ入力されたとする。この場合に、それぞれの有効パルスとその一つの前の有効パルスとにより形成される各区間では、次の式（２８）から加算値が決定され、積算がされる。
【０１０９】
【数１１】

【０１１０】
ここで、Ｈ（ｉ）：ある区間の実時間
Ｇ（ｉ）：ある区間の実効測定時間
ｎ：有効パルス数
【０１１１】
図５の例の場合において、第１区間では、加算値１４／１０＝１．４、第２区間では、加算値８／６＝１．３、第３区間では、加算値１５／１５＝１．０が得られる。なお、図５の例では、説明のために数値は無単位で示している。
【０１１２】
このような計算により、式（２８）により得られる積算値から計数率の実時間の平均値が次の式（２９）から求められる。
【０１１３】
【数１２】

【０１１４】
ここで、Ｈ（ｉ）：ある区間の実時間
Ｇ（ｉ）：ある区間の実効測定時間
ｎ：有効パルス数
【０１１５】
一方、加算値決定手段１０ｂでは、放射線検出信号が入力される毎に放射線検出信号とそれ以前の最後の有効な放射線検出信号の実効測定時間間隔に対する実時間間隔の比率の２乗を加算値ｂとして決定し、計数値記憶手段１１ｂの前記波高範囲に割当てられた記憶器にて加算値ｂを積算し記憶する。
【０１１６】
計算機９は、計数値記憶手段１１ａの積算値と実測定時間を読出し、その積算値を実測定時間で除することにより計数率の実時間平均を算出する。また、計算機９は、計数値記憶手段１１ｂの積算値を読出し、その積算値の平方根を実測定時間で除することにより計数率の実時間平均の計数統計誤差の範囲の推定値を算出する。
【０１１７】
このように第１６実施の形態によれば、測定対象物１２内の放射性物質の分布の不均一性による計数率変動の影響を受けることなく、計数率の実時間平均およびそれらの計数統計誤差による偶発誤差の範囲の推定値を正しく求めることができる。
【０１１８】
次に、図６に示す本発明の第１７実施の形態について説明する。
【０１１９】
第１７実施の形態は、第１実施の形態、第２実施の形態、第８実施の形態乃至第１０実施の形態を具体的に本発明に適用して、配管１６内を流れた放射線を吸収し易い元素の位置についての平均濃度を求める。そして、流速は一定であるとの条件から、放射線源７と放射線検出器２に挟まれた範囲の放射線を吸収しやすい元素の量の時間平均を算出するようにしている。
【０１２０】
ここで、放射線計数装置１には、放射線を吸収しやすい元素が含まれている測定対象溶液１５を一定速度で流す配管１６と放射線計数装置１のデータ処理用の計算機９が接続されている。
【０１２１】
放射線計数装置１は、放射線源７に対して配管１６を介して位置に配置された放射線検出器２と前置増幅器３と主増幅器４と波高弁別器５と放射線検出信号が入力される毎に放射線検出信号とそれ以前の最後の有効な放射線検出信号の実効測定時間間隔の対数と実時間間隔の積を加算値として決定する機能を有する加算値決定手段１０および計数値記憶手段１１により構成される。なお、加算値決定手段１０および計数値記憶手段１１は、加算値および積算値を浮動小数点方式の実数として扱うようにしている。
【０１２２】
以上の構成で、放射線源７から発生した放射線８が放射線検出器２に入射すると、測定対象溶液１５の濃度等に応じて入射する波高値が変化して入力する。従って、波高弁別器５より弁別される波高範囲を越える放射線検出信号のみが加算値決定手段１０に入力される。加算値決定手段１０では、次の式（３０）によって放射線検出信号が入力される毎に放射線検出信号とそれ以前の最後の有効な放射線検出信号の実効測定時間間隔の対数と実時間間隔の積を加算値として決定する。
【０１２３】
【数１３】

【０１２４】
ここで、Ｈ（ｉ）：ある区間の実時間
Ｇ（ｉ）：ある区間の実効測定時間
ｎ：有効パルス数
【０１２５】
ところで、上記式（３０）の第１項について説明すると、発明が解決しようとする課題で説明した前記式（１６）において対数をとると次の式（３１），式（３２）が得られる。
【０１２６】
ｌｎＲ＝−σ・ρ・ｔｌｎＲｏ−−−−（３１）
ρ＝（１／σ・ｔ）・ｌｎ（Ｒｏ／Ｒ）＝ＫｌｎＧ（ｉ）−−−（３２）
【０１２７】
ここで、 Ｒ：計数率
ρ：濃度（密度）
ｔ：試料の厚さ
Ｒｏ：試料がない場合の計数率
σ：試料の放射線に対する吸収計数
Ｋ：定数
そして、第２項との積によりあるパルス区間の物質量が求められる。
【０１２８】
計数値記憶手段１１の前記波高範囲に割当てられた記憶器にて加算値を積算し記憶する。計算機９では、計数値記憶手段１１の積算値と実測定時間を読出し、次の式（３３）により放射線を吸収しやすい物質の量の実時間平均をもとめる。
【０１２９】
物質量の実時間平均＝積算値／実時間−−−−（３３）
【０１３０】
これを測定対象溶液１５内の放射線を吸収しやすい元素濃度に変換する。
【０１３１】
このように第１７実施の形態によれば、測定対象溶液１５内の放射線を吸収しやすい元素の濃度の変動に伴う計数率変動の影響や吸収物質量と計数の非線形関係の影響を受けることなく、測定目的である放射線を吸収しやすい元素の濃度の時間平均を正しく求めることができる。
【０１３２】
次に、図７に示す本発明の第１８実施の形態について説明する。
【０１３３】
第１８実施の形態は、第１実施の形態、第６実施の形態乃至第８実施の形態、第１１実施の形態、第１２実施の形態乃至第１４実施の形態を具体的に本発明に適用したものである。
【０１３４】
本実施の形態は、配管１６内を流れた放射性物質量および放射線を吸収し易い元素の位置について平均濃度を求めることであり、前者は配管１６内の測定対象溶液１５のうち、放射線検出器２付近の放射性物質から発生した放射線８ａの計数率の位置平均から算出することを手段とし、後者は放射線源７と放射線検出器２に挟まれた範囲の放射線を吸収しやすい元素の量の位置平均から算出することを手段としている。
【０１３５】
ここで、放射線計数装置１には、放射性物質と放射線を吸収しやすい元素が含まれている測定対象溶液１５を流す配管１６と配管１６中の測定対象溶液１５の時間当たりの流量およびその時間積分を計る流量計１７と測定対象溶液１５に含まれる放射性物質と異なるエネルギーの放射線を放出する放射線源７およびデータ処理用の計算機９が接続されている。
【０１３６】
また、放射線計数装置１は、放射線源７に対して配管１６を介して配置された放射線検出器２と前置増幅器３と主増幅器４と波高弁別器５と放射線検出信号が入力される毎に放射線検出信号とそれ以前の最後の有効な放射線検出信号の実効測定時間間隔に対する実時間間隔の比率と流量計１７により計られた時間当たりの流量の積を加算値として決定する機能を有する加算値決定手段１０ａと放射線検出信号が入力される毎に放射線検出信号とそれ以前の最後の有効な放射線検出信号の実効測定時間間隔の対数に、実時間間隔と流量計１７により計られた時間当たりの流量の積を加算値として決定する機能を有する加算値決定手段１０ｂと計数値記憶手段１１ａ，１１ｂにより構成されている。
【０１３７】
なお、加算値決定手段１０ａ，１０ｂと計数値記憶手段１１ａ，１１ｂは、加算値および積算値を浮動小数点方式の実数として扱うようにしている。
【０１３８】
以上の構成で、測定対象溶液１５の放射性物質から発生した放射線ａおよび放射線源７から発生した放射線ｂが放射線検出器２に入射すると、波高弁別器５より弁別されたそれぞれの波高範囲の値に応じて放射線検出信号が加算値決定手段１０ａ，１０ｂに入力される。
【０１３９】
加算値決定手段１０ａでは、放射線検出信号が入力される毎に放射線検出信号とそれ以前の最後の有効な放射線検出信号の実効測定時間間隔に対する実時間間隔の比率と、流量計１７により計られた時間当たりの流量の積を加算値ａとして決定し、次の式（３４）により積算値を得る。
【０１４０】
【数１４】

【０１４１】
ここで、Ｈ（ｉ）：ある区間の実時間
Ｇ（ｉ）：ある区間の実効測定時間
Ｆ（ｉ）：ある区間の時間当たりの流量値
ｎ：有効パルス数
【０１４２】
加算値決定手段１０ｂは、放射線検出信号が入力される毎に放射線検出信号とそれ以前の最後の有効な放射線検出信号の実効測定時間間隔の対数し実効時間間隔と流量計１７により計られた時間当たりの流量の積を加算値ｂとして決定し、計数値記憶手段１１ｂの前記波高範囲に割当てられた記憶器にて次の式（３５）に基づいて加算値ｂを積算し記憶する。
【０１４３】
【数１５】

【０１４４】
ここで、Ｈ（ｉ）：ある区間の実時間
Ｇ（ｉ）：ある区間の実効測定時間
Ｆ（ｉ）：ある区間の時間当たりの流量値
ｎ：有効パルス数
【０１４５】
計算機９は、計数値記憶手段１１ａの積算値と流量計１７の流量の時間積分値である実効測定時間を読出し、測定対象溶液１５に含まれる放射性物質から発生する放射線のエネルギーに相当するチャンネルの積算値を流量の時間積分値で除することにより計数率の位置平均を算出し、これを測定対象溶液１５内の放射性物質量へ変換する。
【０１４６】
また、計算機９は、計数値記憶手段１１ｂの積算値を読出し、放射線源７から発生する放射線のエネルギーに相当するチャンネルの積算値を流量の時間積分値で除することにより測定対象溶液１５内の放射線を吸収しやすい物質の量の位置平均と線形な量を算出し、測定対象溶液１５内の放射線を吸収しやすい元素濃度に変換する。
【０１４７】
このように第１８実施の形態によれば、測定対象溶液１５内の放射性物質の分布の不均一性による計数率変動の影響や、放射線を吸収し易い元素の濃度の変動に伴う吸収物質量と計数の非線形関係の影響および測定対象溶液１５の流量変動の影響を受けることなく、計数率の位置間平均および測定目的である放射性物質濃度および放射線を吸収しやすい元素の位置平均を正しく求められる。
【０１４８】
このように本発明による第１実施の形態乃至第１８実施の形態によれば、計数率の実時間平均、計数率の位置平均、放射線を吸収する物質の量の実時間平均、放射線を吸収する物質の量の位置平均、その他放射線計数により求めようとする量が正確に得られる。
【０１４９】
これらの測定値の誤差範囲の推定値のうちの一つ、あるいは複数を測定中における種々の条件の変動の影響を受けずに、かつ、同時に正しく求められる。
【０１５０】
【発明の効果】
以上説明したように請求項１の発明によれば、有効な放射線検出信号が入力される毎にその間の放射線検出に基づく情報を用いて加算値を決定し積算し、測定時間中に放射線検出に基づく情報の変化があっても、有効な放射線検出信号の入力毎である最小期間毎に加算値を決定し、計数値に与える影響を最小限に抑え、正確な計数率を得ることができ、さらに、統計誤差値が最小期間毎に加算値として積算し、得られる全体の統計誤差値も正確なものとなり、計数率に対して正しい評価をすることができる。
【０１５３】
また、請求項２の発明によれば、有効な放射線検出信号毎である最小期間毎に実効測定時間の対数値と実時間の積を加算値として決定し順次積算するようにしたために実効測定時間や物質の濃度等に変化があっても最小期間毎に加算され、しかも、線形な量を計数するから計数値に与える誤差を最小値とし、移動物質の速度が一定の場合、得られた計数値に基づいて移動物質の実時間平均を正確に得ることができる。
【０１５４】
また、請求項３の発明によれば、有効な放射線検出信号毎である最小期間毎に実時間と実効測定時間の対数値と移動物質の速度との積を加算値として決定して順次積算するようにしたために実効測定時間に変化があっても最小期間毎に加算し、しかも、線形な量を計数するから計数値に与える誤差が最小値とし、得られた計数値に基づいて移動物質の位置平均を正確に得ることができる。
【図面の簡単な説明】
【図１】本発明の第１実施の形態を示す放射線計数装置の構成図である。
【図２】本発明の第１３実施の形態を示す放射線計数装置の構成図である。
【図３】本発明の第１６実施の形態を示す放射線計数装置の構成図である。
【図４】図３の放射線計数装置の第１の作用を示す説明図である。
【図５】図３の放射線計数装置の第２の作用を示す説明図である。
【図６】本発明の第１７実施の形態を示す放射線計数装置の構成図である。
【図７】本発明の第１８実施の形態を示す放射線計数装置の構成図である。
【図８】従来の放射線計数装置を示す構成図である。
【図９】放射線の検出に当たって第１の不感時間を示す説明図である。
【図１０】放射線の検出に当たって第２の不感時間を示す説明図である。
【符号の説明】
１ 放射線計数装置
２ 放射線検出器
３ 前置増幅器
４ 主増幅器
５ 波高弁別器
６ 計数記憶器
７ 放射線源
９ 計算機
１０ 加算値決定手段
１１ 計数値記憶手段
１６ 配管
１７ 流量計[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a radiation counting device suitable for correctly measuring radiation of a measurement object.
[0002]
[Prior art]
FIG. 8 shows a conventional example of a radiation counting device. The radiation counting device 1 includes a radiation detector 2, a preamplifier 3, a main amplifier 4, a wave height discriminator 5, and a count storage 6.
[0003]
Here, each time the radiation detector 2 detects the radiation 8 emitted from the radiation source 7 such as radioactive waste, the radiation detector 2 converts the energy of the radiation 8 into an electric signal. The preamplifier 3 amplifies the electric signal output from the radiation detector 2. The main amplifier 4 further amplifies the electric signal amplified by the preamplifier 3 and converts it into a pulse signal having a wave height proportional to the energy of the radiation 8. At this time, if the next radiation is detected at an interval shorter than the time width of the pulse signal, the two pulse signals may overlap to reduce the number of pulses and may not be a wave height proportional to the energy of the radiation. Some of the main amplifiers 4 have a function of judging a pulse that has no longer a wave height proportional to the energy of the radiation 8 as an invalid pulse. The wave height discriminator 5 discriminates whether the wave height of the output pulse of the main amplifier 4 belongs to one or a range separated by a plurality of boundaries.
[0004]
If the next pulse is output from the main amplifier 4 before the end of the discrimination, the pulse height discriminator 5 ignores the pulse as an invalid pulse. In addition, the pulse height discriminator 5 has a time period during which the pulse output from the main amplifier 4 becomes valid as a result of the radiation 8 being detected by the radiation detector 2, that is, a time period during which the pulse is the effective measurement time or becomes invalid. There is a function of outputting a band, that is, a signal indicating whether it is a dead time, and a function of displaying a ratio of the time zone to the real time within a short time.
[0005]
Here, the dead time and the effective measurement time described above are generally described. In almost all detectors, there is a minimum time required for two events to be recorded as two separate pulses. This minimum separation time is called the dead time of the counter. Due to the random nature of radioactive decay, an event occurs immediately after the previous event, which can be recorded and lost.
[0006]
Regarding the behavior of the dead time of the counting device, two models of a "paralysable" type and a "non-paralysable" type are often used.
[0007]
First, the "paralysis" will be described with reference to FIG.
[0008]
When the input pulse has a time width and two or more overlap as shown in FIG. 9 (this is called pulse up) and both become invalid (because the wave height information is lost), the pulse width is insensitive. Time. Since a second dead time is generated by the second pulse input during the dead time due to the first pulse, the circuit becomes paralyzed if this continues. In this case, if the true count rate is n, the apparent count rate (actually measured count rate) is m, and the pulse width is τ, the following equation (1) is given.
[0009]
(Equation 1)

[0010]
On the other hand, the “non-parasitic type” will be described with reference to FIG.
[0011]
When invalidating the next pulse input during the time required for AD conversion or the like of the peak value of a valid input pulse, the dead time is the time required for AD conversion or the like, but the invalidated second pulse is AD Since the conversion is not performed, no new dead time occurs and the circuit does not paralyze. In this case, the following equation (2) holds.
[0012]
n = m / (1-mτ) --- (2)
[0013]
M / n = effective measurement time / real time in both cases of the “parasitic type” and the “non-parasitic type”.
[0014]
The counting memory 6 includes an integer type memory for a part or all of the wave height range divided by the wave height discriminator 5, that is, for each channel, and is provided for both the main amplifier 4 and the wave height discriminator 5. The pulse determined as valid is added by 1 to the stored value of the memory of the channel of the channel in the peak range discriminated by the pulse height discriminator 5 or subtracted from the stored value. Further, the counting memory 6 is provided with a memory for counting the measuring time separately, and counts the elapsed time from the start of the measurement for either or both of the real time and the effective measuring time. The value stored in the count storage 6 is read into the computer 9 and, for example, data such as calculating the count rate in each channel by dividing the count value of each channel of the radiation detection signal by the count value of the effective measurement time. Processing and analysis are performed.
[0015]
[Problems to be solved by the invention]
However, the above-described radiation counting apparatus 1 has a problem that the number of correct radiations cannot be counted as described below.
[0016]
First, first, as described above, the conventional technique counts the number of radiations detected within the effective measurement time, and the count rate obtained by dividing the count value by the effective measurement time is the effective rate. The average count rate is obtained for the measurement time. Therefore, if there is a change in the counting rate during the measurement, the expected value of the time interval of radiation detection changes, thereby causing the ratio between the effective measurement time and the real time in a short time around each time to become inconsistent, As for the count rate, the average for real time and the average for effective measurement time have different values, and it is difficult to obtain an accurate average for real time.
[0017]
For example, in the case of using the radiation counting device 1 shown in FIG. 8, for example, there is a case where there is a “parallel” dead time of τ = 50 μsec and measurement is performed for 1000 seconds (real time).
[0018]
Assume that the true count rate in the first 500 seconds is 1 kcps (1000 pulses per second) and the true count rate in the second 500 seconds is 10 kcps (10000 pulses per second). The true average count rate in 1000 seconds is represented by the following equation (3).
[0019]
(1 kcps × 500 sec + 10 kcps × 500 sec) / 1000 sec = 5.5 kcps-(3)
[0020]
However, according to the actual measurement, the actual measurement count value in the first 500 seconds is expressed by the following equation (4).
[0021]
(Equation 2)

[0022]
The effective measurement time is represented by the following equation (5).
[0023]
(Equation 3)

[0024]
The actually measured count value in the latter 500 seconds is represented by the following equation (6).
[0025]
(Equation 4)

[0026]
The effective measurement time is represented by the following equation (7).
[0027]
(Equation 5)

[0028]
Therefore, for 1000 seconds, the sum of the count values is represented by the following equation (8).
[0029]

Further, the total of the effective measurement times is expressed by the following equation (9).
Total effective measurement time = 476 + 303 = 779 (sec) --- (9)
Therefore, the average count rate is represented by the following equation (10).
Average count rate = 3508268/779 = about 4504 = 4.5 kcps-(10)
[0030]
The average count rate of 4.5 kcps obtained by equation (10) does not match the true count rate of 5.5 kcps obtained by equation (3).
[0031]
Here, considering the first 500 seconds, the formula (11) of (real time / effective measurement time) × count value is obtained.
(500/476) × 475615 = about 500000 --- (11)
Considering the latter 500 seconds, the formula (12) of (real time / effective measurement time) × count value is obtained.
(500/303) × 3032653 = about 500000 --- (12)
When the sum of these values is divided by the total measurement time (real time), the following equation (13) is obtained.
(500000 + 500000) /1000=5500=5.5kcps --- (13)
[0032]
Therefore, it matches the true count rate. In the above example, it is assumed that there is no change in the count rate during the period of 500 seconds, and it is difficult to obtain a correct count rate if the effective measurement time changes.
[0033]
Secondly, when measuring while relatively scanning the object to be measured, if there is a change in the scanning speed within the measurement time, the measurement time for each position of the object to be measured will not be constant, and the time of the counting rate will not be constant. The position average of the count rate cannot be obtained from the average count rate obtained from the count value that is the integral value.
[0034]
That is, for example, when the count rate is proportional to the concentration, the relationship between the flow rate, the concentration, and the count is considered.
[0035]
First, in the first 500 seconds, 1 l / sec (flow rate), 100 g / l (concentration), and 100 cps (count) are obtained, and in the second 500 seconds, 2 l / sec (flow rate), 200 g / l (concentration). , 200 cps (count). In this case, the average for 1000 seconds is 1.5 l / sec (flow rate), 150 g / l (concentration), 150 cps (count), and the following equations (14) and (15) are obtained.
[0036]
True total dissolved mass = (500 × 1 × 100 + 500 × 2 × 200) = 25000 (g) --- (14)
Total dissolved mass by average count rate = 1000 × 1.5 × 150 = 225000 (g) --- (15)
[0037]
Thus, the true total dissolved mass based on the equation (14) does not match the total dissolved mass based on the average count rate according to the equation (15).
[0038]
Third, when the amount to be obtained and the count rate are not in a linear relationship, for example, when the concentration of the substance to be obtained is a function of the logarithm of the count rate as in an absorption densitometer, As is clear from the fact that the time integral value is not proportional to the time integral value of the substance to be obtained, the time average of the amount to be obtained is obtained from the average count rate obtained from the count value which is the time integral value of the count rate. Can not be obtained. For example, when the density (concentration) of a substance is measured by transmission of radiation as in an X-ray photograph, the following formula (16) is obtained from the count rate R by the density (concentration) ρ and the sample thickness t.
[0039]
(Equation 6)

[0040]
In the above case, the following equations (17), (18), (19), and (20) are obtained.
[0041]
The average is (100 × 500 + 200 × 500) / 1000 = 150-(17)
[0042]
(Equation 7)

[0043]
The average count rate for 1000 seconds is
(3032653 + 18339397) / 1000 = about 4872 = 4.87 kcps --- (20)
[0044]
The following equation (21) is obtained by inversely calculating ρ by the above equations (18), (19) and (20).
[0045]
(Equation 8)

Thus does not match the average.
[0046]
Therefore, the present invention provides a radiation counting apparatus capable of correctly measuring a time average, a position average, and the like of an amount to be obtained even if a counting rate or a scanning speed of an object to be measured changes within a measurement time. Aim.
[0047]
[Means for Solving the Problems]
According to a first aspect of the present invention, a radiation detector detects radiation emitted from a radiation source by a radiation detector, converts the radiation into an electric signal, and counts and stores an effective radiation detection signal as a peak pulse signal proportional to the energy of the radiation. In the counting device, each time a valid radiation detection signal is input, first addition value determination means for determining an addition value of the valid radiation detection signal by a predetermined procedure using information based on the radiation detection time during the input. And first count value storage means for accumulating the addition values obtained by the first addition value determination means and storing the count value of the effective radiation detection signal. Second addition value determining means for determining an addition value for obtaining a statistical error value by a predetermined procedure using information based on the radiation detection time of the second time. It is obtained so as to include a second count value storing means for storing the statistical error value to evaluate the count value obtained by by integrating the added value obtained first count value storing means by determining means. With the above means, each time a valid radiation detection signal is input, an added value is determined and integrated using information based on radiation detection during that period. As a result, even if there is a change in information based on the radiation detection during the measurement time, the influence on the count value is minimized because the added value is determined for each minimum period, which is every valid radiation detection signal input. An accurate count rate can be obtained. Further, the statistical error value is integrated as an added value for each minimum period, and an accurate overall statistical error value can be obtained. Therefore, it is possible to correctly evaluate the obtained counting rate.
[0050]
According to a second aspect of the present invention, a moving substance to be measured is disposed between a radiation source and a radiation detector, and radiation transmitted through the moving substance from the radiation source is detected by the radiation detector to generate an electric signal. In a radiation counting device that counts and stores effective radiation detection signals as pulse height pulse signals proportional to the energy of radiation, each time a valid radiation detection signal is input, the effective radiation detection signal and its one Addition value determining means for determining the product of the logarithmic value of the effective measurement time between the immediately preceding effective radiation detection signal and the real time as an addition value, and a count value for integrating the addition value obtained by the addition value determination means Storage means. With the above means, the product of the real time and the logarithmic value of the effective measurement time is determined as an added value for each minimum period that is each valid radiation detection signal, and is sequentially integrated. As a result, even if there is a change in the effective measurement time, the concentration of the substance, or the like, it is added for each minimum period, and since the linear amount is counted, the error given to the count value becomes the minimum value. Therefore, when the speed of the moving substance is constant, the real-time average of the moving substance can be accurately obtained based on the obtained count value.
[0051]
According to a third aspect of the present invention, a radiation detector detects radiation from a moving substance including a radiation emission object to be measured and converts the radiation into an electric signal, and the radiation is effective as a pulse height pulse signal proportional to the energy of the radiation. In a radiation counting device that counts and stores detection signals, every time a valid radiation detection signal is input, the real time between the valid radiation detection signal and the immediately preceding valid radiation detection signal is calculated as the effective measurement time. And a count value storage means for integrating the addition value obtained by the addition value determination means to determine a product of the value divided by the speed and the velocity of the moving substance as an addition value. is there. By the above means, the product of the ratio of the real time to the effective measurement time and the speed of the moving substance is determined as an added value for each minimum period, which is each effective radiation detection signal, and is sequentially integrated. As a result, even if there is a change in the effective measurement time, it is added for each minimum period, so that the error given to the count value by the effective measurement time is the minimum value. Therefore, the position average of the moving substance can be accurately obtained based on the obtained count value.
[0052]
BEST MODE FOR CARRYING OUT THE INVENTION
FIG. 1 is a configuration diagram of a radiation counting device according to a first embodiment of the present invention.
[0053]
In FIG. 1, the same reference numerals as in FIG. 8 showing the conventional example denote the same or corresponding parts, and the main difference between FIG. 1 and FIG. 10 and the count value storage means 11 are provided.
[0054]
Here, the addition value determination means 10 determines an addition value to be integrated by a predetermined procedure using information that changes with the radiation detection time every time a radiation detection signal is input from the wave height discriminator 5. Things. The count value storage means 11 has a function of integrating the addition values obtained by the addition value determination means 10.
[0055]
According to the above configuration, every time the radiation detection signal is input to the addition value determination unit 10, for example, the ratio between the effective measurement time and the real time, and the time such as the speed at which the radiation detector 2 scans the measurement target are set. Using the information that changes together with this, the addition value is determined by a procedure predetermined according to the measurement purpose, and the addition value is integrated and stored by the count value storage unit 11. Therefore, the value obtained as an integrated value is accurate, and the value obtained as an integrated value is determined according to the purpose of measurement, not the integrated value of the effective measurement time of the count rate, because the added value is determined using information obtained from the smallest section as small as possible. For example, if the purpose of the measurement is to obtain a real-time average of the count rate, the real-time integration of the count rate can be used.
[0056]
In addition, as a second embodiment, the addition value determination means 10 and the count value storage means 11 may be configured to handle the addition value and the integrated value as real numbers in a floating-point system.
[0057]
According to this configuration, each time a radiation detection signal is input to the addition value determination unit 10, the addition value corresponding to the measurement purpose is determined as a floating-point real number using other information that changes with time, The count value storage means 11 accumulates and stores the added value as a floating-point real number. Therefore, even when the added value or the integrated value needs to be a real number for the measurement purpose, the measurement purpose can be achieved from the integrated value stored in the count value storage unit 11.
[0058]
As a third embodiment, as compared with the first embodiment, in the example shown in FIG. 1, the addition value determination procedure in the addition value determination means 10 obtains an average count rate for real time by integrating. Value may be used.
[0059]
According to this configuration, each time a radiation detection signal is input to the addition value determination unit 10, the addition value for the purpose of obtaining the average count rate for real time is calculated using other information that changes with time. After the determination, the added value is integrated and stored by the count value storage means 11. Therefore, the average count rate for real time can be correctly obtained from the integrated value stored in the count value storage means 11.
[0060]
Note that, as a fourth embodiment, as compared to the first embodiment, in the example shown in FIG. 1, the addition value determination procedure in the addition value determination means 10 is performed in the actual measurement time within a short time including time. It may be added that the ratio of time is used as the added value.
[0061]
According to this configuration, every time a radiation detection signal is input to the addition value determination unit 10, the ratio of the real time to the effective measurement time within a short time including the time is determined as the addition value, and the count value storage unit 11 The added value is integrated and stored. Therefore, the number of detected radiations is compensated by invalidating the radiation detection signal, and the integrated value stored in the count value storage unit 11 is divided by the total real time to obtain the average count rate for the real time. Can be
[0062]
In the example shown in FIG. 1 as the fifth embodiment with respect to the first embodiment, the procedure for determining the added value in the added value determining means 10 is the same as that of the first embodiment. Add the ratio of the radiation detection signal to the actual measurement value of the effective measurement time interval measured for the effective measurement time of the signal time interval for the effective measurement time and the actual measurement time interval actually measured for the time interval of the last valid radiation detection signal before that for the real time It may be a value.
[0063]
According to this configuration, every time the radiation detection signal is input to the addition value determination unit 10, the time interval between the radiation detection signal and the last valid radiation detection signal before that is measured for the effective measurement time and the real time, respectively. The ratio of the actual measured value of the actual time interval to the actual measured value of the actual time interval is determined as an added value, and the added value is integrated and stored by the count value storage means 11. Therefore, the reciprocal of the effective measurement time interval, that is, the integration of the count rate in real time is obtained, and the integrated value stored in the count value storage means 11 is divided by the total real time to obtain the average count for real time. Rate is obtained.
[0064]
In addition, in the example shown in FIG. 1 as the sixth embodiment with respect to the first embodiment, the addition value determination procedure in the addition value determination means 10 is integrated to obtain an average of the position of the measurement object. The value at which the count rate can be obtained may be added.
[0065]
According to this configuration, each time a radiation detection signal is input to the addition value determination unit 10, addition is performed for obtaining an average count rate for the position of the measurement object using other information that changes with time. The value is determined, and the added value is integrated by the count value storage means 11 and stored. Therefore, the average count rate for the position of the measurement object can be correctly obtained from the integrated value stored in the count value storage unit 11.
[0066]
Note that, in the example shown in FIG. 1 as the seventh embodiment with respect to the first embodiment, the addition value determination procedure in the addition value determination means 10 is performed in real time with respect to the effective measurement time within a short time including time. The product of the ratio of the measurement object and the relative moving speed of the measurement object and the radiation detector (not shown) may be used as the addition value.
[0067]
According to this configuration, every time the radiation detection signal is input to the addition value determination unit 10, the ratio of the real time to the effective measurement time within a short time including the time, and the relative moving speed of the measurement object and the radiation detector Is determined as an addition value, and the addition value is integrated by the count value storage means 11 and stored. Accordingly, the compensation of the number of radiation detections due to the invalidation of the radiation detection signal and the compensation of the difference in the measurement time at each position of the measurement object are simultaneously performed, and the integrated value stored in the count value storage means 11 is used as the measurement object. Dividing by the relative total travel of the radiation detector gives the average count rate for the position.
[0068]
Note that, in the example shown in FIG. 1 as the eighth embodiment with respect to the first embodiment, the addition value determination procedure in the addition value determination means 10 is the same as the radiation detection signal and the last valid radiation detection The ratio of the actual measured time interval between the radiation detection signal and the last effective radiation detection signal before the effective measurement time interval measured for the effective measurement time and the actual measured time interval measured for the effective measurement time. The relative movement speed between the measurement object and the radiation detector not to be used may be set as the added value.
[0069]
According to this configuration, every time the radiation detection signal is input to the addition value determination unit 10, the time interval between the radiation detection signal and the last valid radiation detection signal before that is measured for the effective measurement time and the real time, respectively. The product of the ratio of the measured value of the actual time interval to the measured value of the effective measurement time interval and the relative moving speed of the object to be measured and the radiation detector is determined as an addition value, and the addition value is integrated and stored by the count value storage means 11. I do. Accordingly, the reciprocal of the effective measurement time interval, that is, integration of the count rate at the moving distance is obtained, and the integrated value stored in the count value storage means 11 is divided by the relative total moving distance between the measurement object and the radiation detector. By doing so, an average count rate for the position is obtained.
[0070]
Note that, in the example shown in FIG. 1 as the ninth embodiment with respect to the first embodiment, the addition value determination procedure in the addition value determination means 10 is integrated to calculate the amount of the substance which has transmitted radiation. May be used as the added value.
[0071]
According to this configuration, each time a radiation detection signal is input to the addition value determination unit 10, the average of the amount of the substance that transmits radiation in real time is determined using other information that changes with time. The target addition value is determined, and the addition value is integrated by the count value storage means 11 and stored. Therefore, the average of the amount of the substance that transmits radiation in real time can be correctly obtained from the integrated value stored in the count value storage unit 11.
[0072]
Note that, in the example shown in FIG. 1 as the tenth embodiment with respect to the first embodiment, the addition value determination procedure in the addition value determination means 10 is the same as the radiation detection signal and the last valid signal of the same channel before that. Logarithm of the effective measurement time interval and the last valid radiation detection signal of the same channel before the radiation detection signal were measured in real time The product of the actual time interval measured values may be used as the added value.
[0073]
According to this configuration, each time a radiation detection signal is input to the addition value determination unit 10, the time interval between the radiation detection signal and the last valid radiation detection signal of the same channel before that is defined as the effective measurement time and the real time. Each is measured, the product of the logarithmic value of the effective measurement time actual value and the actual time actual measurement value is determined as an addition value, and the addition value is integrated by the count value storage means 11 and stored. The quantity of a substance is linearly related to the logarithm of the intensity of the radiation transmitted through it, and the logarithmic value of the radiation count rate is integrated in real time and divided by the total real time to obtain the time average of the quantity of the substance. Can be The reciprocal of the interval in the effective measurement time of the radiation detection signal is the counting rate at that time, and the integrated value of the logarithmic value of the effective measurement time interval multiplied by the real time interval is the time average of the amount of the substance. It is proportional to the value whose sign is inverted. Therefore, from the value obtained by inverting the sign of the integrated value stored in the count value storage means 11 and dividing by the total real time, the average of the amount of the substance which transmits radiation in real time can be correctly obtained.
[0074]
Note that, in the example shown in FIG. 1 as the eleventh embodiment with respect to the first embodiment, the addition value determining procedure in the addition value determining means 10 is integrated to obtain the amount of the radiation-transmitted substance. The value at which an average can be obtained for the position of the measurement object may be used as the added value.
[0075]
According to this configuration, each time a radiation detection signal is input to the addition value determination unit 10, the average of the amount of the substance that transmits radiation with respect to the position of the measurement target is calculated using other information that changes with time. An added value for the purpose of obtaining is determined, and the counted value storage means 11 accumulates and stores the added value. Therefore, an average can be easily obtained from the integrated value stored in the count value storage unit 11 with respect to the position of the amount of the substance that transmits radiation.
[0076]
In addition, in the example shown in FIG. 1 as the twelfth embodiment with respect to the first embodiment, the addition value determination procedure in the addition value determining means 10 is the same as the radiation detection signal and the last valid signal of the same channel before that. Logarithm of the effective measurement time interval and the last valid radiation detection signal of the same channel before the radiation detection signal were measured in real time The product of the actual measurement value of the actual time interval and the relative moving speed of the measurement object (not shown) and the radiation detector may be used as the addition value.
[0077]
According to this configuration, each time a radiation detection signal is input to the addition value determination unit 10, the time interval between the radiation detection signal and the last valid radiation detection signal of the same channel before that is defined as the effective measurement time and the real time. Each is actually measured and the product of the logarithmic value of the effective measurement time actual measurement value, the real time actual measurement value, and the relative moving speed of the measurement object and the radiation detector is determined as an addition value, and the addition value is integrated by the count value storage means 11. Remember. The amount of a substance is linearly related to the logarithm of the intensity of the radiation that has passed through it, and the logarithmic value of the radiation count rate is integrated over the relative position of the object and the radiation detector and divided by the total travel distance. Gives the position average of the substance amounts. The reciprocal of the interval at the effective measurement time of the radiation detection signal is the counting rate at that time, and the logarithmic value of the effective measurement time interval is multiplied by the travel distance at that time interval, that is, the actual time interval and the travel speed. The integrated value is proportional to the value obtained by inverting the sign of the position average of the amount of the substance. Accordingly, the sign of the integrated value stored in the count value storage means 11 is inverted, and the value obtained by dividing the value by the relative total moving distance between the measurement object and the radiation detector is used to calculate the average of the position of the amount of the substance that transmits radiation. Is obtained correctly.
[0078]
Next, FIG. 2 is a configuration diagram of a radiation counting device according to a thirteenth embodiment of the present invention.
[0079]
In FIG. 2, the same reference numerals as in FIG. 8 showing the conventional example indicate the same or corresponding parts, and the main difference between FIG. 2 and FIG. This means that means 10a and 10b and a plurality of count value storage means 11a and 11b are provided.
[0080]
Here, the added value determination means 10a and 10b determine a value to be integrated by a predetermined procedure using information that changes with the radiation detection time every time a radiation detection signal is input. The count value storage means 11a, 11b accumulates the addition values obtained by the addition value determination means 10a, 10b.
[0081]
According to the above configuration, each time a radiation detection signal is input to the plurality of addition value determination means 10a and 10b, for example, the measurement of the radioactive substance amount and the radiation absorption substance amount are performed using information that changes with the radiation detection time. For example, a plurality of added values corresponding to each of the plurality of measurement purposes are determined, and the plurality of counted value storage means 11a and 11b accumulate and store the added values for each of the measurement purposes. Therefore, a plurality of measurement purposes can be simultaneously achieved from the plurality of integrated values stored in the plurality of added value determination means 10a and 10b.
[0082]
As a fourteenth embodiment, as compared with the thirteenth embodiment, in the example shown in FIG. 2, the addition value determination procedure in one addition value determination means 10a is integrated, and the other addition value determination means 10b The value at which the variance of the random error of the integrated value of the added value determined by the following formula is obtained may be used as the added value.
[0083]
According to this configuration, each time a radiation detection signal is input to the plurality of additional value determination means 10a and 10b, at least one additional value corresponding to the measurement purpose is determined using information that changes with the radiation detection time. An added value for the purpose of evaluating the range of the random error of the integrated value of the added values is determined, and the added values are independently integrated and stored by the plurality of count value storage means 11a and 11b. Therefore, at least one measurement purpose can be achieved from the plurality of integrated values stored in the plurality of count value storage means 11a and 11b, and at the same time, the random error evaluation of the measurement purpose can be easily achieved.
[0084]
For example, the variance of the random error due to the fluctuation of the counting statistic becomes the integrated value itself as in the case of the counting according to the related art when the added value is always 1, but otherwise, the fluctuation of the counting statistic of one added value is obtained. The variance of the random error due to the counting statistical fluctuation described above can be obtained by separately adding the variance of the random error due to the above.
[0085]
For example, a counting statistical error value is obtained from the following equation (22).
[0086]
(Equation 9)

[0087]
Here, F '(i): a differential value of a function of an added value between a certain effective radiation detection signal and a preceding effective radiation detection signal.
n: Number of valid radiation detection signal sections
i: signal pulse in a section of a certain effective radiation detection signal
[0088]
It should be noted that, as a fifteenth embodiment, as compared with the thirteenth embodiment, in the example shown in FIG. 2, the addition value determination procedure in one addition value determination means 10a is determined by another addition value determination means 10b. A value including the square of the added value as a term may be used as the added value.
[0089]
According to this configuration, each time a radiation detection signal is input by at least one of the plurality of additional value determination means 10a and 10b, the additional value corresponding to the measurement purpose is used by using information that changes with the radiation detection time. Is determined, and the added value is integrated by one count value storage means 11 and stored.
[0090]
Further, another addition value determining means 10 determines the square of the addition value according to the measurement purpose as an addition value, and another counting value storage means 11 accumulates and stores the latter addition value. The square root of the integrated value of the square of the added value according to the measurement purpose corresponds to the random error σ of the added value according to the measurement purpose due to the counting statistical error as shown in the following equation (23).
[0091]
(Equation 10)

[0092]
As described above, at least one measurement purpose is achieved from the integrated value stored in the former count value storage means 11 and at the same time, the accidental value of the measurement purpose is obtained from the integrated value stored in the latter count value storage means 11. Error evaluation can be easily achieved.
[0093]
Next, a sixteenth embodiment shown in FIG. 3 will be described.
[0094]
In the sixteenth embodiment, the first to fifth embodiments and the thirteenth to fifteenth embodiments are specifically applied to the present invention.
[0095]
Here, the radiation counting device 1C includes a measurement target 12 containing a radioactive substance, a motor 13 for rotating the measurement target at a constant speed, and a collimator 14 for narrowing radiation 8 generated from the radioactive substance in the measurement target. And a computer 9 for data processing of the radiation counting device 1 is connected.
[0096]
Further, the radiation counting apparatus 1 receives the radiation detector 2, the preamplifier 3, the main amplifier 4, the wave height discriminator 5, and the radiation detection signal, which are arranged at positions via the collimator 14 with respect to the measurement object 12. Each time the radiation detection signal is input, the radiation detection signal is input to the additional value determination unit 10a having a function of determining the ratio of the real time interval to the effective measurement time interval of the radiation detection signal and the last effective radiation detection signal before that as an additional value. Addition value determination means 10b and count value storage means 11a each having a function of determining the square of the ratio of the real time interval to the effective measurement time interval between the radiation detection signal and the last effective radiation detection signal before that as the addition value. And count value storage means 11b.
[0097]
The addition value determination means 10a and 10b and the count value storage means 11a and 11b handle the addition value and the integrated value as real numbers in a floating-point system.
[0098]
With the above configuration, the radiation 8 generated from the radioactive substance within the range narrowed down by the collimator 14 out of the measurement object 12 rotated at a constant speed by the motor 13 enters. As a result, the radiation detection signal is input to the added value determination means 10a and 10b together with the value of the pulse height range discriminated by the pulse height discriminator 5.
[0099]
As shown in FIGS. 4 and 5, the added value determination means 10a calculates the ratio of the real time interval to the effective measurement time interval between the radiation detection signal and the previous effective radiation detection signal each time the radiation detection signal is input. The sum is determined as the sum a, and the sum of the sum a is stored in the memory assigned to the peak range in the count value storage means 11a.
[0100]
More specifically, FIG. 4 shows the operation of each device when a radiation detection signal is input to the radiation detector 2, and the radiation detector 2 outputs a pulse-like signal only instantaneously when the radiation detection signal is input. Is output, and the preamplifier 3 converts the waveform into an illustrated waveform by the CR circuit and outputs the converted waveform to the main amplifier 4. Then, it is amplified by the main amplifier 4 as a mountain-like waveform shown in the figure. In this case, as shown in the left side of the figure, when the peak waveform overlaps from the main amplifier 4 and is input to the wave height discriminator 5, the wave height discriminator 5 causes the overlapped short wave as shown in the upper part of the figure at the time of the paralysis dead time. On the other hand, the A / D conversion is started at the time of the non-parasitic dead time, but the pile-up is detected and interrupted as shown in the figure.
[0101]
In response to this, the count value storage unit 11a stops counting the clock by setting the clock of the effective measurement time to RUN → STOP. As a result, the addition of the effective measurement time is excluded during this period.
[0102]
As shown at the bottom of the figure, when the previous valid radiation detection signal is input at time t1 and the valid radiation detection signal is input at time t2, the real time and the effective measurement time are expressed by the following equations ( 24) and Equation (25).
[0103]
Real time = time t2-time t1 ---- (24)
Effective measurement time = Actual time − ｛(time tc−time ta) −−−−−− (25)
[0104]
Further, in the embodiment of the present invention, in the section from the time t2 to the time t1, the added value for the next counting and the added value for the counting statistical error are determined. First, the addition value determining means 10a determines an addition value for each section with respect to the following equation (26).
[0105]
Addition value = (real time / effective measurement time)----(26)
[0106]
Further, the addition value determining means 10b determines an addition value for each section with respect to the following equation (27).
[0107]
Addition value = (real time / effective measurement time) squared-(27)
[0108]
More specifically, as shown in FIG. 5, an n-th effective radiation detection signal (illustrated first effective pulse) from a first effective radiation detection signal (illustrated first effective pulse) is sent to the main amplifier 4. It is assumed that input has been made. In this case, in each section formed by each effective pulse and the immediately preceding effective pulse, an added value is determined from the following equation (28) and integrated.
[0109]
(Equation 11)

[0110]
Here, H (i): actual time of a certain section
G (i): Effective measurement time of a certain section
n: number of effective pulses
[0111]
In the example of FIG. 5, the added value 14/10 = 1.4 in the first section, the added value 8/6 = 1.3 in the second section, and the added value 15/15 = 1 in the third section. .0 are obtained. In the example of FIG. 5, numerical values are shown in unitless units for the purpose of explanation.
[0112]
With such a calculation, the average value of the count rate in real time is obtained from the following equation (29) from the integrated value obtained by equation (28).
[0113]
(Equation 12)

[0114]
Here, H (i): actual time of a certain section
G (i): Effective measurement time of a certain section
n: number of effective pulses
[0115]
On the other hand, each time the radiation detection signal is input, the addition value determination means 10b adds the square of the ratio of the real time interval to the effective measurement time interval between the radiation detection signal and the last effective radiation detection signal before the addition value b. And the storage value assigned to the peak height range of the count value storage means 11b accumulates and stores the addition value b.
[0116]
The computer 9 reads the integrated value and the actual measurement time of the count value storage means 11a, and calculates the average of the count rate in real time by dividing the integrated value by the actual measurement time. The computer 9 reads the integrated value of the count value storage means 11b, and divides the square root of the integrated value by the actual measurement time to calculate an estimated value of the count statistical error range of the real time average of the count rate.
[0117]
As described above, according to the sixteenth embodiment, the real-time average of the count rates and the statistical error of the counts are used without being affected by the count rate fluctuation due to the non-uniform distribution of the radioactive material in the measurement object 12. The estimated value of the range of the random error can be correctly obtained.
[0118]
Next, a seventeenth embodiment of the present invention shown in FIG. 6 will be described.
[0119]
In the seventeenth embodiment, the first embodiment, the second embodiment, and the eighth to tenth embodiments are specifically applied to the present invention to absorb radiation flowing in the pipe 16. The average concentration at the position of the element that is easy to determine is determined. Then, based on the condition that the flow velocity is constant, the time average of the amount of the element that easily absorbs radiation in the range between the radiation source 7 and the radiation detector 2 is calculated.
[0120]
Here, the radiation counting device 1 is connected to a pipe 16 through which a measurement target solution 15 containing an element that easily absorbs radiation flows at a constant speed, and a computer 9 for data processing of the radiation counting device 1.
[0121]
The radiation counting device 1 is provided with a radiation detector 2, a preamplifier 3, a main amplifier 4, a wave height discriminator 5, and a radiation detection signal which are arranged at positions with respect to a radiation source 7 via a pipe 16. It is composed of an addition value determination means 10 and a count value storage means 11 having a function of determining the product of the logarithm of the effective measurement time interval of the radiation detection signal and the last effective radiation detection signal before that and the real time interval as an addition value. You. The addition value determination means 10 and the count value storage means 11 handle the addition value and the integrated value as real numbers in a floating-point system.
[0122]
With the above configuration, when the radiation 8 generated from the radiation source 7 enters the radiation detector 2, the incident peak value changes according to the concentration of the measurement target solution 15 and the like, and is input. Therefore, only the radiation detection signals exceeding the peak range discriminated by the peak discriminator 5 are input to the addition value determining means 10. Each time the radiation detection signal is input according to the following equation (30), the addition value determination means 10 multiplies the logarithm of the effective measurement time interval between the radiation detection signal and the last effective radiation detection signal before that by the real time interval. Is determined as an addition value.
[0123]
(Equation 13)

[0124]
Here, H (i): actual time of a certain section
G (i): Effective measurement time of a certain section
n: number of effective pulses
[0125]
By the way, when the first term of the above equation (30) is explained, the following equations (31) and (32) are obtained by taking the logarithm of the equation (16) described in the problem to be solved by the invention.
[0126]
lnR = −σ · ρ · tlnRo-(31)
ρ = (1 / σ · t) · ln (Ro / R) = KlnG (i)-(32)
[0127]
Where: R: counting rate
ρ: concentration (density)
t: sample thickness
Ro: counting rate when there is no sample
σ: Absorption coefficient of sample for radiation
K: constant
Then, the amount of the substance in a certain pulse section is obtained by the product of the second term.
[0128]
The added value is integrated and stored in a storage unit of the counted value storage unit 11 assigned to the peak height range. The computer 9 reads out the integrated value and the actual measurement time of the count value storage means 11 and obtains the real time average of the amount of the substance which easily absorbs radiation by the following equation (33).
[0129]
Real time average of substance amount = integrated value / real time --- (33)
[0130]
This is converted into an element concentration that easily absorbs radiation in the solution 15 to be measured.
[0131]
As described above, according to the seventeenth embodiment, without being affected by the change in the counting rate due to the change in the concentration of the element that easily absorbs the radiation in the solution 15 to be measured and the non-linear relationship between the amount of the absorbed substance and the count. In addition, the time average of the concentration of the element that easily absorbs radiation, which is the measurement object, can be correctly obtained.
[0132]
Next, an eighteenth embodiment of the present invention shown in FIG. 7 will be described.
[0133]
In the eighteenth embodiment, the first, sixth to eighth, eleventh, and twelfth to fourteenth embodiments are specifically applied to the present invention. It was done.
[0134]
In this embodiment, the amount of the radioactive substance flowing in the pipe 16 and the average concentration of the position of the element which easily absorbs the radiation are determined. The former is the radiation detector 2 of the solution 15 to be measured in the pipe 16. By calculating from the position average of the count rate of the radiation 8a generated from the nearby radioactive material, the latter is the position average of the amount of the element which easily absorbs the radiation in the range between the radiation source 7 and the radiation detector 2. Is calculated from
[0135]
Here, the radiation counting device 1 includes a pipe 16 through which a measurement target solution 15 containing a radioactive substance and an element that easily absorbs radiation, a flow rate per unit time of the measurement target solution 15 in the pipe 16 and a time integration thereof. A flowmeter 17 for measuring the temperature, a radiation source 7 for emitting radiation having energy different from the radioactive substance contained in the solution 15 to be measured, and a computer 9 for data processing are connected.
[0136]
Further, each time the radiation detector 2, the preamplifier 3, the main amplifier 4, the wave height discriminator 5, and the radiation detection signal are input to the radiation source 7 via the pipe 16 with respect to the radiation source 7, An addition value having a function of determining, as an addition value, a product of the ratio of the real time interval to the effective measurement time interval of the radiation detection signal and the last effective radiation detection signal before that, and the flow rate per time measured by the flow meter 17. Each time the determination means 10a and the radiation detection signal are input, the logarithm of the effective measurement time interval between the radiation detection signal and the last effective radiation detection signal before that is calculated, and the real time interval and the time per hour measured by the flow meter 17 are used. It comprises an addition value determination means 10b having a function of determining the product of the flow rates as an addition value, and count value storage means 11a and 11b.
[0137]
The addition value determination means 10a and 10b and the count value storage means 11a and 11b handle the addition value and the integrated value as real numbers in a floating-point system.
[0138]
With the above configuration, when the radiation a generated from the radioactive substance of the solution 15 to be measured and the radiation b generated from the radiation source 7 enter the radiation detector 2, the values of the respective pulse height ranges discriminated by the pulse height discriminator 5 are obtained. Accordingly, the radiation detection signal is input to the added value determination means 10a, 10b.
[0139]
Each time the radiation detection signal is input, the addition value determination unit 10a measures the ratio of the radiation detection signal and the actual time interval to the effective measurement time interval of the last valid radiation detection signal before that, and the flow rate meter 17. The product of the flow rates per time is determined as the added value a, and the integrated value is obtained by the following equation (34).
[0140]
[Equation 14]

[0141]
Here, H (i): actual time of a certain section
G (i): Effective measurement time of a certain section
F (i): Flow rate value per hour in a certain section
n: number of effective pulses
[0142]
Each time the radiation detection signal is input, the addition value determination means 10b calculates the logarithm of the effective measurement time interval between the radiation detection signal and the last effective radiation detection signal before that, and the effective time interval and the time measured by the flow meter 17. The product of the per-flow rate is determined as an addition value b, and the storage value assigned to the peak range of the count value storage means 11b is integrated and stored based on the following equation (35).
[0143]
(Equation 15)

[0144]
Here, H (i): actual time of a certain section
G (i): Effective measurement time of a certain section
F (i): Flow rate value per hour in a certain section
n: number of effective pulses
[0145]
The computer 9 reads out the integrated measurement value of the count value storage means 11a and the effective measurement time which is the time integration value of the flow rate of the flow meter 17, and reads out the channel corresponding to the energy of radiation generated from the radioactive substance contained in the solution 15 to be measured. The position average of the counting rate is calculated by dividing the integrated value by the time integral value of the flow rate, and this is converted into the amount of radioactive substance in the solution 15 to be measured.
[0146]
Further, the computer 9 reads out the integrated value of the count value storage means 11b, and divides the integrated value of the channel corresponding to the energy of the radiation generated from the radiation source 7 by the time integrated value of the flow rate, thereby obtaining the measured value in the solution 15 to be measured. A position average and a linear amount of the amount of the substance that easily absorbs radiation are calculated, and converted into an element concentration that easily absorbs radiation in the solution 15 to be measured.
[0147]
As described above, according to the eighteenth embodiment, the influence of the counting rate fluctuation due to the non-uniform distribution of the radioactive substance in the measurement target solution 15 and the amount of the absorbing substance due to the fluctuation of the concentration of the element that easily absorbs radiation can be reduced. The position-to-position average of the counting rate and the position average of the radioactive substance concentration and the element that easily absorbs radiation, which are the measurement objects, can be correctly obtained without being affected by the nonlinear relationship of the counting and the flow rate fluctuation of the solution 15 to be measured.
[0148]
As described above, according to the first to eighteenth embodiments of the present invention, the real-time average of the count rate, the position average of the count rate, the real-time average of the amount of the substance absorbing the radiation, and the absorption of the radiation The position average of the amount of the substance and other amounts to be obtained by radiation counting can be obtained accurately.
[0149]
One or more of the estimated values of the error range of these measured values can be correctly obtained at the same time without being affected by variations in various conditions during measurement.
[0150]
【The invention's effect】
According to the first aspect of the present invention as described above,Each time a valid radiation detection signal is input, the added value is determined and integrated using the information based on the radiation detection during that period. Even if there is a change in the information based on the radiation detection during the measurement time, the valid radiation detection signal The addition value is determined for each minimum period, which is the input of each, the influence on the count value is minimized, an accurate count rate can be obtained, and the statistical error value is integrated as the addition value for the minimum period. In addition, the obtained overall statistical error value is also accurate, and the count rate can be correctly evaluated.
[0153]
According to the second aspect of the present invention, the product of the logarithmic value of the effective measurement time and the real time is determined as an addition value for each effective period of the radiation detection signal for each minimum period, and is sequentially integrated. Even if there is a change in the concentration of substances or the like, they are added every minimum period, and since the linear amount is counted, the error given to the count value is minimized. Based on the numerical values, the real-time average of the mobile substances can be obtained accurately.
[0154]
According to the third aspect of the present invention, the product of the logarithmic value of the real time and the effective measurement time and the speed of the moving material is determined as an added value for each effective radiation detection signal for each minimum period and sequentially integrated. Therefore, even if there is a change in the effective measurement time, it is added every minimum period, and since the linear amount is counted, the error given to the count value is set to the minimum value, and based on the obtained count value, the transfer material is determined. The position average can be obtained accurately.
[Brief description of the drawings]
FIG. 1 is a configuration diagram of a radiation counting device according to a first embodiment of the present invention.
FIG. 2 is a configuration diagram of a radiation counting apparatus according to a thirteenth embodiment of the present invention.
FIG. 3 is a configuration diagram of a radiation counting apparatus according to a sixteenth embodiment of the present invention.
FIG. 4 is an explanatory diagram showing a first operation of the radiation counting device of FIG. 3;
FIG. 5 is an explanatory diagram showing a second operation of the radiation counting device of FIG. 3;
FIG. 6 is a configuration diagram of a radiation counting device according to a seventeenth embodiment of the present invention.
FIG. 7 is a configuration diagram of a radiation counting device according to an eighteenth embodiment of the present invention.
FIG. 8 is a configuration diagram showing a conventional radiation counting device.
FIG. 9 is an explanatory diagram showing a first dead time in detecting radiation.
FIG. 10 is an explanatory diagram showing a second dead time in detecting radiation.
[Explanation of symbols]
1 Radiation counting device
2 Radiation detector
3 Preamplifier
4 Main amplifier
5 Wave height discriminator
6 Count storage
7 radiation sources
9 Calculator
10 Addition value determination means
11 Count value storage means
16 Piping
17 Flow meter

Claims (3)

A radiation counting device that detects radiation emitted from a radiation source by a radiation detector, converts the radiation into an electric signal, and counts and stores an effective radiation detection signal as a peak pulse signal proportional to the energy of the radiation. Each time a detection signal is input, first addition value determination means for determining an effective addition value of the radiation detection signal by a predetermined procedure using information based on the radiation detection time during the detection signal, and the first addition value First count value storage means for accumulating the added value obtained by the determination means and storing a count value of a valid radiation detection signal, each time the valid radiation detection signal is input, based on a radiation detection time therebetween A second added value determining means for determining an added value for obtaining a statistical error value by a predetermined procedure using the information; and a second added value determining means. The radiation counting device for adding value obtained integrated to the characterized by including a second count value storing means for storing the statistical error value to evaluate the count value obtained by said first count value storing means. Placing a moving substance that is a measurement target between a radiation source and a radiation detector, and detecting radiation that has passed through the moving substance from the radiation source by the radiation detector and converting the radiation into an electric signal. In a radiation counting device that counts and stores valid radiation detection signals as pulse height pulse signals proportional to the energy of radiation, every time a valid radiation detection signal is input, the valid radiation detection signal and the previous valid Additional value determining means for determining the product of the logarithmic value of the effective measurement time between the actual radiation detection signal and the real time as an additional value, and count value storing means for integrating the additional value obtained by the additional value determining means. A radiation counting device, comprising: A radiation detector detects radiation from a moving substance containing radiation emission, which is the object to be measured, and converts it into an electrical signal.At the same time, it counts and stores the effective radiation detection signal as a peak pulse signal proportional to the radiation energy. In the radiation counting apparatus, each time a valid radiation detection signal is input, the value obtained by dividing the real time between the valid radiation detection signal and the immediately preceding valid radiation detection signal by the effective measurement time and the movement A radiation counting apparatus comprising: an addition value determination unit that determines a product of a material velocity and an addition value as an addition value; and a count value storage unit that integrates the addition value obtained by the addition value determination unit .

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