Thermal Analyzing On G-M Cryocooler-cooled Superconducting Magnet System

The cryocooler-cooled superconducting magnet has been widely used in areas of high field due to its simple configuration,compact parts and helium-free.G-M cryocoolers is mainly used to cool down small superconducting magnets at present.To varying version of G-M cryocooler,traditional method,with little help estimating accurate temperature of tow cold heads and choosing suitable G-M cryocooler,preferred to use higher heat loss to estimate whether a cryocooler had enough power to cool down magnet.To improve the accuracy of estimating temperature of tow cold heads,this paper offer a method that can precisely estimate temperature of combining with magnet and G-M cryocooler.Cooling feature which contained revelance between two cold heads is a kind of curve obtained by balance of heat experiment.The paper present a mode of cooling feature function through analyzing variety of heat losses based on thermodynamics.Based on this function an 24 sets of data from Cooling feature curve,the paper obtains mathematic revelance between temperature of cold heads and cooling power using 1Stopt software.The paper uses 10 T Nb3Sn superconducting magnets system.The temperature of two cold heads T1,T2,which is different from traditional method,is unknown when functions of heat losses and Cooling feature curve solved.The temperature of two cold heads solved by C language is set as initial value of boundary conditions in simulation.Optimization of lowest heat loss of binary current leads was made and shape parameters are determined.Temperature field of current leads is also simulated.The model of magnet system is built based on the outcoming calculated by magnetic field analyzing part of ANSYS APDL.Setting temperature of two cold heads form theory calculation as boundary condition,Simulation is performanced through Workbench.The final temperature field indicated that the temperature of two cold heads fits well to cooling feature curve after four simulations.Deformation of radiation shield,vacuum shell and HTS current leads caused by thermal stress is analyzed under this kind of deployment with RSDK-408D2 cryocooler through Workbench simulation.C language is used to estimate affection due to variation of magnetic field on magnet system temperature field during excitation.Optimal excitation speed is confirmed through variation of magnet temperature along with time after C language programme has been done.The paper use this magnet temperature to check if cryocooler we choosed is qualified in excitation process.