Simulation of HPGe Detector Efficiencies by Monte Carlo Methods

Abstract

The HPGe detector, being a gamma nuclide dosimeter, is generally used in the laboratory for monitoring environmental radiation. In order to maintain accuracy of the measurements, it is necessary to do regular maintenance and calibration of the dosimetry criteria for the detector. With diverse samples, the shape and volume of the containers will be different. The various sampling for the same sample might also result in large difference in the density. Due to the limitation of the present techniques and resources in Taiwan, only important items of efficiency calibration are included in the process of HPGe detector calibration, e.g. energies, densities and sample shapes. Interpolated or extrapolated values are employed when the exact efficiency calibration data are not available. This might cause considerable errors to the sampling measurement value. In order to reduce measurement errors and reduce experiment times consuming, this paper presents a method to calculate the peak efficiency of the HPGe detector by using the Monte Carlo code EGS4. This code has been performed to compute the gamma-ray spectrum and the influence of absolute peak efficiency with various source volumes. This study compares the theoretical calculation results with experimental data measured from the Radiation Laboratory of the Taiwan Power Company. It shows good agreement for the related cases of different source energy, source volume and source-detector distance.