Evidence that transverse variability of critical current density can greatly mitigate screening current stress in high field REBCO magnets

, where RE=rare earth) coated conductors by screening current stress (SCS) is a significant concern for ultra-high-field superconducting magnets. Indeed, the third Little Big Coil (LBC3), a REBCO magnet that generated a record, high field of 45.5 T, showed wavy plastic damage produced by excess SCS in all pancakes except two made with single-slit conductors having their slit edges pointing inward towards the magnet center. Reasons for this slit edge orientation-dependent damage mitigation having not yet been presented, we made it the central issue of this new Little Big Coil (LBC4). Accordingly, we constructed and tested LBC4 by replicating LBC3, except that only single-slit tapes were used and every slit edge pointed inward towards the magnet center. LBC4 reached 44.0 T without quench but with some dissipation. After a small lowering of the current without disappearance of the dissipati…