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本文报道了一台由Ge(Li)主探测器和环形NaI(Tl)反符合探测器组成的高灵敏度γ谱仪的结构、性能和应用。谱仪用交替的物质屏蔽和井形NaI(Tl)反符合屏蔽降低本底。Ge(Li)探测器的体积为78cm~3,对~(60)Co 的1332keVγ射线的分辨率为2.42keV,不加任何屏蔽时峰康比为36.4,相对效率为16%,对~(187)Cs 点源γ射线全能峰的探测效率为1.6%。本谱仪在不加和加反符合屏蔽时,对~(137)Cs 点源的峰康比分别为79和333;康普顿区积分抑制因子为3.67,康普顿端抑制因子为5.2;在50—2700keV 能量范围内,本底抑制因子为3.2。在物质屏蔽和反符合屏蔽条件下,在上面的能量范围内,谱仪本底为24cpm。对~(137)Cs 点源,当测量时间为1000min、置信水平为95%时,谱仪的最小探测限(判断限)为2.2×10~(-2)Bq(0.59pCi)。本谱仪主要用于分析测量环境样品和其他低水平放射性样品中发射γ射线的核素的含量。
This paper reports the structure, performance and applications of a highly sensitive gamma spectrometer consisting of a Ge (Li) main detector and a circular NaI (Tl) anti-coincidence detector. The spectrometer reduces the background by alternate material shielding and well NaI (Tl) anti-coincidence shielding. The Ge (Li) detector has a volume of 78cm-3, a resolution of 2.42 keV for 1332 keV gamma rays of ~ (60) Co, a 36.4% relative efficiency of 16.4% without any shielding, ) The detection efficiency of the Cs point source γ-ray all-around peak was 1.6%. The spectrometer’s peakconcentrations for point sources of 137Cs were 79 and 333, respectively, when the spectra were not added and anti-matched, the ICC constants were 3.67 and the Compton-end inhibitory factor was 5.2. In the 50-2700keV energy range, the background suppression factor is 3.2. In the material shielding and anti-matching shielding conditions, in the above energy range, the spectrometer background is 24cpm. For 137Cs source, the minimum detection limit of the spectrometer is 2.2 × 10 -2 Bq (0.59 pCi) when the measurement time is 1000 min and the confidence level is 95%. The spectrometer is mainly used to analyze γ-ray-emitting radionuclides in environmental samples and other low-level radioactive samples.