Engineering Design and Novel Winding Approaches in Developing High Quality HTS REBCO Coils

Abstract

With recent challenges in developing hightemperature superconductor coils using rare-earth barium copper oxide (REBCO) conductor, particularly critical current degradation in a fully wet wound coil using traditional epoxy, we present engineering stress analysis and new winding approaches in its coil fabrication in order to produce high quality coils. Its implementation, however, necessitates novel approaches and nonconventional considerations. This paper first calculates stress and analyzes stress concentration in the REBCO coil in processes of coil winding and thermal cycling. Thus, a thin film layer has been added to reduce the stress concentration on the coil winding. Second, it describes the critical current anisotropic properties and apply to a Helmholtz coil design to draw attentions to develop a full matrix of I <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">c</sub> (B, T, φ) data for various magnet designs. In the coil fabrication, it introduces a dry winding method with stainless steel cowind (metallic insulation) that has been applied and successfully delivers high quality high temperature superconductor (HTS) coils. Additionally, it tries a fully wet winding approach but employs alternative epoxy-Araldite and no degradation has been found after a few thermal cycles.