Compact Design of Cryogen-Free HTS Magnet for Laboratory Use

A compact high temperature superconductor magnet cooled by a single stage Gifford-McMahon cryorefrigerator was designed, manufactured and tested. The arrangement of the magnet was optimized to maximize cooling efficiency of the Bi2223/Ag winding and minimize the heat generation by eddy current losses during high-speed excitation. To achieve wide angular access and adequate magnetic field homogeneity in the magnet center a split-pair coil configuration was used. Maximum magnetic field in the magnet center is 1.8 T @ 14.5 K, inner diameter of the magnet winding is 50 mm, outer diameter is 98 mm and total width of the magnet winding including 14.2 mm air-gap is 72 mm. Performance of the magnet was tested also at liquid nitrogen, sub-cooled liquid nitrogen and liquid helium temperatures. New vacuum cryostat system with a free access to the magnet space was designed and manufactured. Calculations of the magnet behavior with iron poles were evaluated and compared with the magnet without iron. Experimental results agree well with the magnet parameters obtained by FEM simulation