Conduction-cooled superconducting magnet with persistent current switch for gyrotron application

A superconducting magnet with a center field of 4.5 T cooled by GM cryocooler and operated in the persistent current mode has been designed, fabricated and tested for gyrotron. The superconducting magnet has a warm bore with diameter of 90 mm, the homogenous region with the diameter of 40 mm and length of 230 mm. The ratio of the axial field to the center field located at 180 mm is lower than 88%. In the other special points, the ratios of the radial field to the axial field should be less than from 3% to 11%. The thermally-controlled NbTi/CuNi switch with superconducting joint is connected to the conduction cooled magnet. In this paper, the detailed design, fabrication and test are reported.