Improvement of Magnetic Field Homogeneity From the HTS Joint-Less Coil

The concept of joint-less winding with 2G high-temperature superconductors (HTS) wide conductors proposed by the authors made HTS magnets possible to realize a persistent-current-mode operation. It could successfully maintain reasonable amount of the persistent current in multiple stacked HTS pancake coils with perfectly closed superconducting loops. In this paper, we applied the same technique to HTS layer winding, so called solenoid winding, to make an improvement of the magnetic field quality. To avoid unfavorable gap near at the center plane of the joint-less winding, we made two identically designed joint-less coils and attached them symmetrically. By this particular design of the coil, we could locate the intrinsic gap of the coil far away from the important magnetic center point. We fabricated the joint-less coil according to the design. During the experiment of the coil to measure the central magnetic field, one of the two coils was found to be damaged after the successful cooling down below 20 K and the charging up the healthy one with a persistent magnetic field of 0.5 T, which was just a half of the expected value. The damaged coil will be replaced with a new one, and tested again in the near future.