Critical Current

The maximum current a superconductor carries before it goes resistive.

Above its critical current (which falls with field and temperature) a superconductor quenches back to normal resistance. Magnet design keeps operation safely below the critical surface; the REBCO study maps it.

Above its critical current — which falls as field and temperature rise — a superconductor quenches back to normal resistance, so magnet design keeps operation safely inside that surface with margin. Kronos's REBCO study maps the critical-current envelope explicitly, because reaching the breeder's and burner's fields means operating near the high-field frontier of it.