A 4 K G-M Refrigerator for Direct Cooling of a 6 T NbTi Superconducting Magnet System
This paper describes the construction and experimental results of a cryocooler cooled NbTi superconducting magnet system. The technical features of this magnet system are a 4K-Gifford-McMahon (GM) refrigerator using magnetic regenerator material and a high-Tc (Bi2Sr2CaCu2Oy;Bi2212) superconducting current lead. The 4K-GM refrigerator with Er3Ni regenerator had the refrigeration capacity of 0.5 W at 4.2 K. The Bi2212 superconducting current lead reduced a heat load to the refrigerator. The NbTi coil was directly cooled by the 4K-GM refrigerator at 3 K level without liquid helium. The available magnetic field of 6 T at operating current of 128 A and the maximum magnetic field of 6.45 T were obtained in the 180 mm room temperature bore.
KeywordsHeat Load Liquid Helium Magnet System Current Lead Regenerator Material
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