【摘要】 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~1.46M eV)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137Cs系统本底且反康抑制达4~5倍,测到4个样品中137Cs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,234Th探测限(0.2~0.4Bq/kg,对63keV)和228Ac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,226Ra(测214Pb352keV峰)探测限有点高(0.7~1Bq/kg),反康未起作用。样品中的40K高达22~144Bq/kg。更多还原

【Abstract】 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 Compton-suppression is discussed.It shows that the Compton background continuum is reduced remarkably about 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 itself.Thanks to no background and with Compton suppression factor of 4~5,137Cs are detected to between 0.03~0.06Bq/kg in four samples,while they are all below the LLDs if without Anti-Compton.The LLDs of 234Th(0.2~0.4Bq/kg,by 63keV) and 228Ac(~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 effect to improve the LLDs for measuring 226Ra(by 352keV of 214Pb) which are somewhat high(0.7~1Bq/kg).40K in four samples is high to 22~144Bq/kg.更多还原