Detect efficiency calibration methods of HPGe γ spectrometer for annularity source

The reaction rates of uranium in the Natural uranium decomposition simulation device is the important data for studying the reliability of neutronics design in the conceptual design of fission cladding in subcritical reactor. The detect efficiency for annularity source in a HPGe spectrometer must be calibrated accurately. We want to apply the Monte-Carlo method to calibrate the efficiency for annularity source and improve the accuracy and efficiency. The detect efficiency curve of point source was measured at the axis of the detector with a 6 cm distance from the surface. The results are obtained by calculation in MCNP5 and the measurements are fit well through adjusting the size of dead layer and hole in the HPGe. Then the detect efficiency for the annularity gamma source is calculated and compared with the measurement result which was measured by integral calculating the point detect efficiency in radial direction, and the comparison will examine the efficiency calibration method. The measured full energy peak efficiency for the annularity gamma source agreed with the simulated value to within 4% in the energy range 200 to 1400 keV. The method is an accurate and efficient way for calibrating the annularity source. (authors)