Effect of heaters on the measurement of normal zone propagation velocity on short YBCO conductors

Abstract

Based on a fully two-dimensional (2D) electrothermal model, the quench propagation characteristics of short superconducting YBa2Cu3O7-x conductors (AMSC and SuperPower), including the minimum quench energy (MQE), normal zone propagation velocity (NZPV) and hot spot temperature rising rate, are studied by numerical simulations in this paper. It is found that different heater configurations, such as the size of heater and the duration of heat pulse, can result variations of the MQEs and NZPVs. During the quench propagation processes, the NZPV and the normal zone length (LNZ), when viewed as functions of the hot spot temperature Tpeak, i.e., NZPV(Tpeak) and LNZ(Tpeak), are not sensitive to the heater configurations for relatively higher operating temperature from 50 K – 70 K. For both AMSC and SuperPower's YBCO conductor, the simulation results show that the hot spot temperature rising rate dTpeak/dt, as a nearly-linear function of Tpeak, is almost not affected by heater configurations for a given fixed operating temperature in the regime 30 – 70 K. For a fixed operating temperature in the regime 30 – 50 K, the temperature rising rate of SuperPower's conductor can reach 1000 K/s ~ 6000 K/s as Tpeak rising from ~110 K to 300 K, which makes it challenging to experimentally determine the NZPV prior the moment Tpeak reaches the temperature limit 300 K. The relations LNZ(Tpeak) obtained for SuperPower's conductor can provide information for the selection of reference voltage employed to determine the NZPV.