Modeling of Minimum Energy Required to Quench an HTS Magnet With a Strip Heater

Abstract

Due to the wide spectrum of current sharing temperatures in a high-temperature superconducting (HTS) magnet, estimating the energy required to quench the magnet is a complicated task. On the other hand, quenching a low-temperature superconducting (LTS) magnet for quench characterization purposes with a heater is straightforward due to the small temperature margin and correspondingly low minimum quench energy (MQE). To estimate the required energy for the LTS magnet, the analytical concept of MQE can be utilized. In this paper, we propose that only numerical simulations can give adequate estimates to the MQE of an HTS magnet, for measurement purposes. Furthermore, due to the high enthalpy margin, the utilization of spot heaters with short energy pulses becomes questionable. We present in detail the effect of heater's pulselength to the MQE, when a strip heater is utilized for quenching. In addition, the effect of the heater area on MQE is studied. We consider the model of a REBCO coil to be constructed and tested in the Enhanced European Coordination for Accelerator Research and Development (EuCARD-2) Project. According to the results: 1) MQE increases almost linearly for pulselengths between 100 and 500 ms; 2) when the heater area is enlarged, the required energy per area saturates to a certain value related to the coil's enthalpy margin; 3) MQE obtained with a traditional analytic approach based on a minimum propagating zone considerably underestimates the numerically obtained MQE.