Fabrication and Test of a Cryocooler Directly Cooled NbTi Superconducting Magnet

The cryocooler directly cooled low temperature superconducting magnet is designed, fabricated and tested at the Korea Basic Science Institute (KBSI) for the crystal growth application. The magnet has one solenoidal configuration with a copper former which has a 52 mm room temperature bore. A two-stage 4 K GM cryocooler with 1.5 W refrigeration power is employed to cool the magnet from room temperature to liquid helium temperature. A pair of the binary current lead, a series combination of a normal conductor in the high temperature section and an HTS conductor in the low temperature section, is used for this application. The paper presents the process of design, fabrication and charging test. Also, the performance of the conduction cooled superconducting magnet system is discussed with respect to the supplied current and contact resistance.