LAUSR

Abstract Rare Earth Barium Copper Oxide (REBCO) High Temperature Superconductor (HTS) tapes are being considered for the Toroidal Field (TF) magnets of a highly compact, high field fusion reactor operating at magnetic fields as high as 21 T and operating temperatures in the range of 10–30 K. Due to the increase in range of operating conditions made available through HTS tapes, a new set of cryogenic fluids are being considered for forced flow cooling. The present study investigates helium, hydrogen, and neon as a forced flow coolant for REBCO HTS tapes used in a highly compact, high-field reactor design. Four design criteria are considered, including current sharing temperature, fluid inlet temperature, cable pressure drop (dP), and operating pressure. From these simulations, neon is removed from consideration due to its high required pressure drop and low temperature margins with respect to the current sharing limit. Helium and hydrogen are then compared, with hydrogen producing the highest overall heat transfer rate at its optimum operating condition (1.5 MPa/15 K). A compromise across inlet temperature, dP, and operating pressure is found when helium has a minimum initial temperature of 10 K and an inlet pressure of 2.0 MPa. For the current design, helium is selected as a coolant due its acceptable cable pressure drop, required cooling load, and system complexity inherent to a forced-flow cryogenic system.