抄録
This paper describes the mechanism of quench-induced dynamic breakdown phenomena of liquid helium (LHe). The dynamic breakdown of LHe is induced under thermal bubble conditions due to quench of a superconducting wire at a considerably lower stress level than the static breakdown voltage without the quench. We measured partial discharge (PD) characteristics of LHe during the process from quench-onset to dynamic breakdown. The results revealed that PD were detected after quench and followed by the dynamic breakdown of LHe. This event corresponds to the process of bubble generation, growth and extinction in the vicinity of the superconducting wire with high electric field strength. There also existed the polarity difference of applied voltage in PD characteristics, i. e. PD were detected only in the negative polarity of superconducting wire. Consequently, PD associated with the thermal bubble behavior were recognized as pre-breakdown phenomena of the quench-induced dynamic breakdown of LHe.
