Stability Study On Cryocooler-Cooled Superconducting Magnet

A cryocooler-cooled superconducting magnet (CSM) has the advantagessuch as compact structure, easy operation and high safety compared witha superconducting magnet immersed in cryogenic liquid. Cryocooler-cooledsuperconducting magnet has become an important tendency insuperconducting magnet technology and application. In order to providethe theoretic basis for the construction of CSM and to solve the realisticproblems encountered in the process of construction, the stabilityproblems of cryocooler-cooled low temperature and high temperaturesuperconducting magnet are investigated in this paper on the basis ofcryocooler's cooling characteristics, thermal loads analysis in themagnet and the differences between low temperature superconductor (LTS)and high temperature superconductor (HTS).The aluminum-stabilized superconduting magnet is one of the mostimportant advanced technologies in dectector magnets of high energyphysics and space detector magnets. If cryocooler-cooledaluminum-stabilized superconducting magnet is adopted for space magnet,the magnet weight will be decreased greatly, dectector operation time willbe increased and the safety will be improved. This paper investigates thestability of aluminum-stabilized superconductor immersed in liquidhelium and cooled by cryocooler. The theoretic analysis and calculationsimulation are conducted by considering the differences ofaluminum-stabilized superconductor and copper-stabilizedsuperconductor.After detailed analyses and calculations of each heat loads incopper-stabilized superconducting magnet, the stability of the magnet atsteady operation and current excitation conditions is studied on the basisof the thermal balance between heat loads and cryocooler cooling power.The simulation results are confirmed well by the experiment results fora 6T CSM for material processing and a 4T high homogeneity CSM.From the different characteristics of HTS and LTS, the thermalstability of a high temperature CSM for magnetic separation isinvestigated. The different stability criterions for cryocooler-cooledlow temperature superconducting magnet and cryocooler-cooled hightemperature superconducting magnet are put forward. The results areproved well with experiments.