Continuous Heating Criteria to Avoid Thermal Runaway of Insulated HTS Coils in High Fields

High-field high temperature superconducting (HTS) coils, in particular REBCO coils, tend to show electromagnetic force-induced degradation and premature thermal runaways. Operation of high-field HTS coils is practicable with resistive voltage if cooling power permits. In this light, understanding coil voltage and the corresponding Joule heating power that may give rise to a thermal runaway is essential for stable magnet operation. In this paper, we report investigations of continuous heating criteria for safe operation, Q
_safe
, and the dependence of Q
_safe
on applied field, operating conductor current density, heating length, cooling condition, and number of coil layers using a numerical simulation based on results of model coil experiment. In addition, Q
_safe
values for actual HTS coils were estimated; the results showed that the simulation can predict Q
_safe
values of actual coils.