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

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.