We have tested an intermediate-size HTS stainless steel double pancake coil (132 turns per coil) and discovered dynamic effects during sudden discharge on millisecond scale. Two main approaches have been compared: soft and hard breaks. The soft break is when the power supply is turned off suddenly but the shunt resistors (168 milliohm) is still connected. The hard break uses a high voltage contactor to suddenly open the circuit so that the DPC leads are completely open. The hard break is dangerous to traditionally insulated low temperature magnets, but the SS-insulated HTS DPC retained integrity over >80 power cycles. Voltage decay curves for the soft and hard breaks are studied on short and long timescales. On long timescales, we observe the expected exponential decay and measure the time constant to calculate contact resistance. On short timescales, we observe highly dynamic effects: a hyper-exponential decay suggesting that the inductance or contact resistance is changing with time, likely an indication of the RL circuit forming.
The authors would like to thank Y. Wang, E. Burkhardt, K. Holland, K. Schrock, and S. Chandrasekaran for their assistance and support at Michigan State University and thank K. Amm and P. Wanderer for general support at BNL. This work was supported by the U.S. Department of Energy Office of Science under Cooperative Agreement DE-SC0000661. Magdelena Allen was funded by the U.S. Department of Energy, Office of Science, Office of Workforce Development for Teachers and Scientists (WDTS) under the Science Undergraduate Laboratory Internships Program (SULI), and thanks Honghai Song for his mentorship at BNL.