Simulation study on transient temperature field characteristics of HPGe detectors simulated by the COMSOL method

BackgroundHigh-purity Ge (HPGe) detectors are widely used in nuclear science, technology, and national defense because of their excellent energy resolution capability, which enables them to fingerprint gamma rays and accurately determine nuclide types and intensities. However, HPGe detectors typically need to be cooled to low temperatures for normal operation to prevent excessive thermal noise at room temperature.PurposeThis study aims to investigate the heat transfer process and temperature distribution law inside a HPGe detector to ensure the stable operation of the detector in a low-temperature environment.MethodsThrough the analysis of the heat transfer mechanism of the high-purity germanium (HPGe) detector, the internal heat transfer structure and a three-dimensional heat transfer model were constructed. COMSOL software was utilized to simulate the internal temperature distribution of the HPGe detector under liquid nitrogen refrigeration, as well as to investigate the effects of varying refrigeration times and packaging structures on this distribution. Based on these simulations, the packaging structure of the HPGe detector was optimized. Additionally, a temperature testing platform for the detector was constructed, and the simulation results were compared with experimental data to validate the model's accuracy.ResultsThe simulation results demonstrate that the detector model achieves dynamic equilibrium after 6 h of cooling, with the minimum internal temperature at the tip of the cold finger approximately -175 ℃. The utilization of oxygen-free copper as the cold chain material, combined with a low heat leakage and high-strength support material for the cold finger, enhances refrigeration efficiency. Additionally, the Dewar is designed with a sidewall thickness of 1.5 mm, and the spacing between the sidewall and the crystal cylinder is set at 3 mm. These design features collectively facilitate the detector's attainment of a lower limiting refrigeration temperature.ConclusionsThe modeling and temperature field simulation methods for HPGe detectors are validated through a consistency comparison between simulated and experimental data. Theoretical support is obtained for the further optimization and improvement of the design parameters of liquid nitrogen and electric cooling HPGe detectors.