Study on Thermal Stability of Conduction-Cooled HTS Coil

One of the features of an HTS coil is its high thermal stability against thermal disturbances and the minimum quench energy of an HTS coil is several orders higher than that of an LTS coil. However, thermal runaways are observed in several conduction-cooled HTS coils. As thermal runaway causes degradation of the HTS coil, it is important to understand how it occurs. We evaluated the thermal stability of a conduction-cooled HTS coil. The HTS coil was composed of four single-pancake coils wound with Ag-sheathed Bi2223 tapes and the inductance of the HTS coil was approximately 3.8 H. The thermal runaway currents of the HTS coil at 15-30 K were measured. The experimental results were found to be in good agreement with the calculated results at 15-30 K.