测定闪烁室对氡及其子体释放的α粒子探测效率的三段法研究

A Three - Counts Method of Measuring Scintillation Cell Detection Efficiency to a Particles Emitting from Radon and Its Progeny

目的 由闪烁室对氡及其子体衰变释放的α粒子的探测效率,求闪烁室测氢浓度的刻度因子。方法根据氡及其短寿命子体218Po(RaA)和214Po(RaC)之间的关系,建立了一种闪烁室测量氡及其子体释放的α粒子的探测效率的三段法。闪烁室采用真空法瞬时从氡室取样,且氡进入闪烁室前用高效率的玻璃纤维滤膜过滤,三段计数时间分别为采样后5-30min,50～90min,120～180min。结果 一个编号为126#的ST-203型闪烁室对氡及其子体衰变释放的α粒子的探测效率的测量结果分别为εRn=0.779±0.019、εRaA=0.871±0.030、εRaC=0.947±0.011,它们的平均值ε测=0.866与该闪烁室按其测氡刻度因子计算的平均探测效率εXRn=0.875±0.022是一致的。当采样流量为5L·min-1时,126#ST-203型闪烁室测(?)浓度的刻度因子KTh=19.3Bq·m-3·(min-1)-1。结论 为确定闪烁室测(?)浓度刻度因子提供一种较可靠的方法。

Objective Our studies were aimed at providing a method to determine the calibration factor of a scintillation cell for thoron concentration measurement based on the scintillation cell detection efficiency to a particles emitting from radon and its progeny. Methods A three - counts method of measuring scintillation cell detection efficiency to a particles emitting from radon and its progeny were developed on the relationship of radon and its progeny .The scintillation cell samples fresh radon gas with a high efficiency of filter by using vacuum sampling.The three counting time intervals are 5 - 30min, 50 - 90min, 120 - 180min after the sampling.Results The detection efficiency of a scintillation cell Model ST- 203 No. 126 to a particles emitting from radon and its progeny are εRn = 0.779 ±0.019, εRaA = 0.871 ±0.030,εRaC = 0.947 ±0.011, respectively, the average value εmeasurement = 0.866 is compatible with EKRn= 0.875 ± 0.022 calculating from its calibration factor for radon concentration measurement. When sampling flow rate is 5L/min, the calibration factor for thoron concentration measurement is K(Th) = 19.3 Bq · m - 3 · (min-1)-1. Conclusions The method developed for determining scintillation cell calibration factor for thoron concentration measurement is effective.