Cooling structure for 6 T NbTi superconducting magnet directly cooled by cryocooler

摘要

This paper describes the cooling structure for a 6 T NbTi superconducting coil directly cooled by a cryocooler. The cooling structure was designed to remove AC loss of the coil lest the coil temperature should exceed the current sharing temperature during coil charging. A copper cylinder surrounding the outer surface of the coil was adopted as the cooling structure. Indium sheet was inserted between the copper cylinder and the coil to improve thermal conductance. Stainless steel wire was wound on the copper cylinder so that the radial stress at the boundary between the copper cylinder and the coil was kept compressive. Temperature difference between the coil inner surface and the copper cylinder was lower than 0.1 K while charging the coil.