Insulation of Coated Conductors for High Field Magnet Applications

Insulation in a high field superconducting magnet plays a critical role. For high field magnets using coated conductor, insulation faces a few special challenges. In order to maximize the engineering current density, the conductor insulation has to be very thin (e.g. <; 12.5 μm). In addition to required mechanical and dielectric integrity under high stresses at cryogenic temperatures, the temperature during insulation process needs to be significantly lower than 200 where degradation of coated conductor may occur. In this paper, we will first review the options for coated conductor insulation. Then we present our UV cured epoxy insulation system developed for insulating coated conductors. This reel-to-reel system is able to coat YBCO tapes or co-winding steel tapes with 10 μm UV cured epoxy. The coating has good dielectric property and shows no cracking or de-bonding in liquid nitrogen under up to 0.75% of applied bending or tensile strains. In addition, a silica sol gel based ceramic coating system has been developed for coating oxides on steel co-winding tapes, taking advantage of excellent thermal properties of the oxides. Some issues of both UV cured epoxy and the sol gel insulation coatings will be discussed.