REBCO Coils With Variable Co-Wind Dimensions Under Static and Cyclic Axial Pressure Loads at 77 K

Abstract

An investigation into the effects of high cycle fatigue on REBCO coils along their axis of rotation was performed to establish design limits. Three coils were tested in liquid nitrogen via a hydraulic materials testing machine. The coils were fabricated with the same type of REBCO tape but had different co-wind materials and dimensions. The results showed that for a coil with REBCO tape wider than its co-wind, where the loads bear directly on the conductor, had 5% permanent critical current degradation at pressures near 100 MPa. A significant improvement was observed in a wax impregnated coil, which aided to distribute loads, with a 1.2% permanent critical current reduction after 50,000 load cycles to 125 MPa. Additionally, a coil with co-wind wider than its REBCO tape was also improved and reached 5% reduction after 50,000 cycles at pressures up to 100 MPa and continued loading to 151 MPa.