中文摘要：

根据点源、面源和体源探测效率之间的函数关系,建立了虚拟源刻度方法;对于大面积及大体积放射源,可将其探测效率进行分割,利用蒙特卡罗输运程序进行计算,然后利用虚拟点源模拟体源峰效率。模拟中,将虚拟点源发射的放射性粒子准直成锥形发射,以方便计算。该方法解决了蒙特卡罗方法计算大源小探测器的小概率输运问题。采用该方法,用HPGe探测器对实验室放射性133 Xe气体样品及航空圆柱状气体烟云探测效率进行了刻度模拟实验,虚拟点源和体源的计算结果一致,证明了该刻度方法正确可靠。

英文摘要：

In monitoring of environmental radioactivity,it is impossible to finish efficiency calibration of HPGe detectors with conventional methods due to the large size of the radioactive sources.In this paper,we propose a virtual source efficiency calibration method which uses a simulated source to calculate the detection efficiency of a large source.In the simulation,the large disk/volume source is divided into several small sources,and by integrating the detection efficiencies of the small sources,the detection efficiency of the large source can be obtained.To avoid the complexity in the calculation,the radioactive particles are supposed to emit in a conical shape from the virtual source.The method was used in efficiency calibration of a HPGeγdetector for a 133 Xe source in a laboratory and a cylindrical radioactive cloud,and the detection efficiency of the virtual source is in agreement with that of the volume source,indicating that the calibration method for virtual source can be used for very large disk/volume sources.