Basic Design of REBCO Insert Coil of 33 T Cryogen-Free Superconducting Magnet

Abstract

A 33 T cryogen-free superconducting magnet (33 T-CSM) is under development. The 33 T-CSM consists of a REBCO insert coil and Nb₃Sn/NbTi outsert coils. The REBCO insert coil is designed to generate 19 T in the external field of 14 T. The REBCO insert coil is composed of stacked 64 single pancake coils wound with two bundled REBCO tapes. The inner and outer diameters of the REBCO insert coil are 68 mm and 295 mm, respectively. The REBCO coil is impregnated with epoxy resin for conduction cooling. To prevent delamination of the superconducting layer by thermal stress, the fluorine-coated polyimide tape is co-wound with REBCO tapes and to prevent degradation of superconductivity by electromagnetic stress, reinforcing tape is also co-wound. According to 2D-FEM, it is shown that the circumferential strain ϵ_θ under applying electromagnetic force is 0.29% . The results of 2D-FEM also suggest that stress concentration occurs at the connection between the coil and the bus bar, and at the widthwise end of the REBCO tape. In this paper, the basic design of the insert coil and the results of FEM analysis will be described.