Quench Characteristics of HTS Conductors at Low Temperatures

Not withstanding their high stability at liquid nitrogen temperatures, quench propagation due local disturbances remains a crucial issue for high temperature superconductors (HTS) operating at low temperatures as high field insert coils and cryogen-free magnets. In contrast to low temperature superconductors (LTS), normal zone in HTS at low temperatures must develop over a much extended temperature range for current sharing with a highly non-linear dependence on temperature. The present work addresses this issue directly using both computer simulation and experimental studies. Several quench characteristics unique to HTS have identified using a comparative study of the underlying quasilinear parabolic equation represented in an appropriate dimensionless form for proper isolation of the known effects of temperature dependence of thermal properties. Most notable and counter-intuitive finding is that the minimum propagation zone (MPZ) was found to increase with transport current. The correlations of minimum quench energy (MQE) and the quench temperature of MPZ with operating temperature and current have been obtained for comparison with experimental results.