High-field flux jump instabilities in cables for accelerator or compact fusion magnets and their effective suppression.

Rare-earth-barium-copper-oxide (ReBCO) superconducting tapes are pivotal for emerging technologies such as fusion reactors and particle accelerators due to their superior performance in high magnetic fields. Despite extensive studies of single tapes, the magnetization behavior of ReBCO tape stack cables at high magnetic fields has been underexplored. Here, we present magnetization measurements of ReBCO tape stack cables at magnetic fields up to 30 T at 4.2 K. Remarkably, flux jump instabilities, typically confined to lower field regimes in single tapes, persisted up to 17 T and higher in tape stacks. Such instabilities could significantly impact the stability and field quality of large-scale superconducting magnets. Crucially, we demonstrate that introducing small intertape spacers substantially mitigates flux jump occurrences, sometimes eliminating them completely. Our findings offer valuable insights for designing stable, high-performance ReBCO cable-based magnets, enhancing their viability for next-generation fusion and accelerator applications.