核电子学与探测技术
覈電子學與探測技術
핵전자학여탐측기술
NUCLEAR ELECTRONICS & DETECTION TECHNOLOGY
2009年
6期
1461-1465,1474
,共6页
反康普顿γ仪%谷物%探测限
反康普頓γ儀%穀物%探測限
반강보돈γ의%곡물%탐측한
Anti-Compton%Gamma-ray Spectrometer%Cereal Crop%LLD
通过比较低本底反康普顿HPGeγ谱仪两种操作模式(有反康和无反康)测量4种谷物样品中放射性活度的异同,讨论反康普顿抑制的优越性.结果显示,有反康时能谱中的康普顿基线本底有显著抑制,从低能区的2倍至高能区的5倍(60keV～1.46MeV)不等.但对特定核素的分析探测限不仅与康普顿本底有关,还与系统自身可能存在的特定能峰的本底净计数率有关.由于无~(137)Cs系统本底且反康抑制达4～5倍,测到4个样品中~(137)Cs比活度在0.03～0.06Bq/kg,而如没有反康则都低于探测限.由于系统中本底几乎可以忽略,~(234)Th探测限(0.2～0.4Bq/kg,对63keV)和~(228)Ac探测限(～0.1Bq/kg,对911keV)有反康时下降了20%～30%.由于测量期间的高氡环境本底,~(226)Ra(测~(214)Pb352keV峰)探测限有点高(0.7～1Bq/kg),反康未起作用.样品中的~(40)K高达22～144Bq/kg.
通過比較低本底反康普頓HPGeγ譜儀兩種操作模式(有反康和無反康)測量4種穀物樣品中放射性活度的異同,討論反康普頓抑製的優越性.結果顯示,有反康時能譜中的康普頓基線本底有顯著抑製,從低能區的2倍至高能區的5倍(60keV～1.46MeV)不等.但對特定覈素的分析探測限不僅與康普頓本底有關,還與繫統自身可能存在的特定能峰的本底淨計數率有關.由于無~(137)Cs繫統本底且反康抑製達4～5倍,測到4箇樣品中~(137)Cs比活度在0.03～0.06Bq/kg,而如沒有反康則都低于探測限.由于繫統中本底幾乎可以忽略,~(234)Th探測限(0.2～0.4Bq/kg,對63keV)和~(228)Ac探測限(～0.1Bq/kg,對911keV)有反康時下降瞭20%～30%.由于測量期間的高氡環境本底,~(226)Ra(測~(214)Pb352keV峰)探測限有點高(0.7～1Bq/kg),反康未起作用.樣品中的~(40)K高達22～144Bq/kg.
통과비교저본저반강보돈HPGeγ보의량충조작모식(유반강화무반강)측량4충곡물양품중방사성활도적이동,토론반강보돈억제적우월성.결과현시,유반강시능보중적강보돈기선본저유현저억제,종저능구적2배지고능구적5배(60keV～1.46MeV)불등.단대특정핵소적분석탐측한불부여강보돈본저유관,환여계통자신가능존재적특정능봉적본저정계수솔유관.유우무~(137)Cs계통본저차반강억제체4～5배,측도4개양품중~(137)Cs비활도재0.03～0.06Bq/kg,이여몰유반강칙도저우탐측한.유우계통중본저궤호가이홀략,~(234)Th탐측한(0.2～0.4Bq/kg,대63keV)화~(228)Ac탐측한(～0.1Bq/kg,대911keV)유반강시하강료20%～30%.유우측량기간적고동배경본저,~(226)Ra(측~(214)Pb352keV봉)탐측한유점고(0.7～1Bq/kg),반강미기작용.양품중적~(40)K고체22～144Bq/kg.
By contrasting two operation modes (with and without Anti-Compton) of a low background gamma-ray spectrometer for radioactivity measurement of four cereal crop samples, the effect of Comp-ton-suppression is discussed. It shows that the Compton background continuum is reduced remarkably a-bout 2 to 5 times from low energy region to high energy region (60keV～1.46MeV) with Anti-Compton.However, the lower limits of detection (LLD) for different nuclides are depend on not only Compton baselines but also net counting rates for specific (peaks which maybe come from the detector system it-self. Thanks to no background and with Compton suppression factor of 4～5, ~(137)Cs are detected to be-tween 0. 03～0.06Bq/kg in four samples, while they are all below the LLDs if without Anti-Compton.The LLDs of ~(234)Th (0. 2～0.4Bq/kg, by 63keV) and ~(228)Ac (～0.1Bq/kg, by 911keV) with backgrounds are almost negligible are decreased 20%～30% by Compton suppression. Due to the high level of Radon in environment during the time of measurment, anti-Compton has no efect to improve the LLDs for measuring ~(226)Ra (by 352keV of ~(214)Pb) which are somewhat high (0. 7～1Bq/kg). ~(40)K in four samples is high to 22～144Bq/kg.
