I. Introduction
Recently, high-temperature superconducting (HTS) wires have been improved to have practical properties, and so various HTS coils have been designed and fabricated [1], [2]. One of the features of HTS coils is high thermal stability against the thermal disturbances. Minimum quench energy (MQE) of HTS coils is several order higher than that of LTS coils. We developed a conductive cooled HTS coil for Si single-crystal growth applications [3], [4]. For fabricating single-crystal silicon of high purity, it is effective to apply the magnetic field to molten silicon during crystal growth. The coil was energized to the rated operating current of 210 A for less than one minute. Quench did not occur in the operation, though the ac loss amounted to over 200 W and the temperature rise of several degrees was observed. We demonstrated the high stability of the HTS coils in dc operations in the experiments.