Determination of dead layer thickness of HPGe detector through simulation and measurement of efficiency calibration curve for radioactive waste analysis of gamma transmitter

Dead layer thickness of HPGe detector is a very important parameter for determining the efficiency of the calibration on the analysis of radionuclide content in radioactive waste. However, information of this thickness is not easily obtained, the data from the detector's manufacturers are generally not accurate, and the dead layer thickness is changed together with the long of time of detector usage. This study was conducted to determine the thickness of dead layer HPGe GC2020 detector which has been used routinely in the laboratory. The determination is done by comparing the results of the calibration curve from measurements in the laboratory with calculation result of MCNP5 program. In the laboratory, the calibration curve is made by measuring of radionuclides standard Cd-109, Co-60, Cs-137, Mn-54 and Co-60 that is placed at position 0, 7.5 and 15 cm from the detector surface. The same curve made in simulation manner by calculating the energy efficiency of each radionuclide based on data detector-source configuration with a dead layer thickness variations of 1-2 mm. It can be concluded that the dead layer thickness was 1.50 mm with a deviation of the simulated curve measurement is less than 8 % in the energy range 80-1400 keV. (author)