Research On Peltier Current Lead With Low Heat Leakage Used In Superconducting DC Devices

The superconductor itself has zero resistance and high current density and thus has wide application in superconducting devices.The superconducting device needs to be operated in a low temperature environment,and the current lead,connecting the power supply and the superconducting device,passes through the temperature range from room temperature(RT)to low temperature(liquid nitrogen or liquid helium),which is one of the main heat leakage sources in the low temperature system.The Peltier current lead(PCL)formed by inserting a thermoelectric material Bi2Te3 at the room temperature end of a conventional copper lead can effectively reduce the heat leakage caused by the current lead,and the heat leakage can be reduced by 30%compared with the conventional copper lead.Based on the research results of PCL at home and abroad,the optimization method for 100 A-class PCL is proposed,and the kA-class PCL has been developed.Firstly,the traditional calculation methods of PCL,such as numerical method and analytical method,were used to optimize,the ratio(L/A)of each part of PCL is calculated,and the initial range is provided for the model of PCL in the COMSOL finite element simulation.The solid heat transfer physics field in the multiphysics finite element simulation software COMSOL is used to establish a two-dimensional axisymmetric model by considering the temperature characteristics of materials in the PCL.After the model is established,the PCL is optimized with the minimum heat leakage of PCL,and the ratio(L/A)of each part in the PCL is determined.Since the resistivity and thermal conductivity of the thermoelectric material and copper in the PCL vary with temperature,in order to further reduce the leakage heat of PCL,so the heat leakage of PCL with varying cross section is analyzed.At the same time,after determining the ratio(L/A)of each part in PCL,the heat leakage of PCL at different current values was analyzed,and the optimal application range of PCL with constant and varying cross section is determined.On the basis of the development of the 100 A-class PCL,the kA-class PCL is developed through the parallel structure.The sample of 100 A-class PCL with constant and varying cross section as well as cooling devices at the room temperature end are fabricated,the experiments of the PCL were carried out in liquid nitrogen(LN2).The heat leakage of PCL was calculated by numerical method.The feasibility of the 100 A-class PCL model was confirmed.The performance of 100 A-class PCL with constant and varying cross section under two cooling modes was analyzed.The heat leakage of kA-class PCL is analyzed by simulating method.After kA-class PCL specimen was fabricated.and the experiment of kA-class PCL was carried out in liquid nitrogen.The current distribution and the temperature at each end of each thermoelectric element of the parallel PCL are measured.The results are agreement with simulated one,the proposed kA-class PCL have potential application for superconducting DC devices with high current capacity.