ABSTRACT In view of the complexity of current detection efficiency calibration of radioactive gas sources, a method using solid planar sources to be equivalent to gas sources was studied. For the 50 mL gas source box, an optimal equivalent scheme was selected by Monte Carlo Simulations. Then, the full-energy-peak efficiency curve of gas sources at the measurement position of 25 cm, with source-to-detector distance of 25 cm, was fitted by measuring solid planar sources with known activity. To verify the accuracy of the efficiency curve, 41Ar, 133Xe and 87Kr gases were produced and determined by length-compensated method. Then, their full-energy-peak efficiencies at 25 cm position away from the detector were directly calibrated. The percentage efficiency deviations between interpolation from the efficiency curve and direct calibration are all less than 2.5%, which proves the accuracy of the equivalent method. This calibration method is a general one and can be also used for some other radioactive sample measurements, such as non-destructive analysis of gaseous fission product samples with a suitable source-to-detector distance.

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HPGe探测器测量放射性气源等效效率标定方法研究

摘要 针对目前放射性气源检测效率标定的复杂性，研究了一种利用固体平面源等效于气源的方法。对于 50 mL 气源箱，Monte Carlo Simulations 选择了最佳等效方案。然后，通过测量已知活度的固体平面源，拟合出测量位置为25 cm、源到探测器距离为25 cm的气源的全能峰效率曲线。为验证效率曲线的准确性，采用长度补偿法制备并测定了 41Ar、133Xe 和 87Kr 气体。然后，直接校准它们在距离探测器 25 cm 位置处的全能量峰值效率。效率曲线插值与直接校准的效率偏差百分比均小于2.5%，证明等效方法的准确性。这种校准方法是一种通用的方法，也可以用于其他一些放射性样品测量，例如具有合适的源到探测器距离的气态裂变产物样品的无损分析。