Cryogen-free HTS coil placed in a heat-exchange gas

Poorly cooled regions in cryogen-free superconducting windings represent weak points especially in high-current-density superconducting windings of superconducting magnets with complicated geometry. It is quite natural taking into account the low average heat conductivity of the superconducting winding. In this paper, we propose to cool the winding mainly not by thermal conductivity but by heat exchange with the low-pressure gaseous helium placed in a hermetic envelope around the winding. The envelope is cooled through its thermal contact with a cooler head. The method was experimentally checked and its advantages are discussed.