Superconducting Current Leads Under Pulsed Current Conditions

Cryogenic superconducting devices such as a Superconducting Magnetic Energy Storage device can require current leads that must operate under conditions where the current is delivered in pulses. The focus of this paper was to observe the electrical and thermal behavior of conduction-cooled superconducting current leads in hopes to develop a better understanding of normal zone propagation when pulsed currents are applied for future design purposes. Leads made of copper tubing soldered in parallel to 2-G HTS tape were made to allow the normal zone propagation to be observed. The leads were evacuated and connected to a power source at one end and the cold finger of a cryocooler at the other end. The test fixture allowed for the temperature and voltage distribution measurements to be made. Pulsed dc current was supplied to allow the observation of lead response as a function of current level for different ramp cycles. A transient 1-D numerical model was also developed to calculate the current lead temperature in space and time. The lead dimensions used in the model match those used in the experiment. Results of the experiment validate the numerical model and are used to develop a better understanding of the thermal and electrical properties of superconducting current leads under pulsed conditions.