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本文报道一台以φ75×75mm 的 NaI(Tl)晶体为主探测器,以φ430×500mm 的环型塑料闪烁体为反符合探测器,以另一φ75×75mm 的 NaI(Tl)晶体为符合探测器所组成的反符合屏蔽低本底γ谱仪。采用含放射性杂质少的结构物质和屏蔽材料,符合、反符合等措施降低本底。在井型反符合屏蔽条件下,主探测器在0.05—2.0MeV 能区内的积分本底为68cpm。对~(137)Cs(φ8mm)面源的能量分辨率为10.5%,全能峰效率为10.9%,康普顿散射减弱因子可达2.1;当测量时间为1000min,置信水平为95%时,面源最小可探测下限为1.13dpm。该谱仪适于环境样品及某些弱放射性样品的测量。
This paper reports a NaI (Tl) crystal detector with a diameter of 75 × 75mm, a ring type plastic scintillator with φ430 × 500mm as an anti-coincidence detector and a φ75 × 75mm NaI (Tl) crystal as a coincidence detector Anti-compliance mask consisting of low background γ spectrometer. The use of structural materials and shielding materials containing less radioactive impurities, compliance, anti-coincidence and other measures to reduce the background. Under well-type anti-coincidence screening conditions, the main detector’s integral background in the 0.05-2.0 MeV energy region is 68 cpm. The energy resolution of ~ (137) Cs (φ8mm) was 10.5%, the peak energy of all-around peak was 10.9%, and the Compton scattering reduction factor was 2.1. When the measurement time was 1000 min and the confidence level was 95% The minimum detectable minimum source is 1.13dpm. The spectrometer is suitable for the measurement of environmental samples and some weak radioactive samples.