Cryogenic Power Control for HTS and LTS Combined Magnets

DOE high-field magnets provide advanced accelerator capabilities for improvements in various physics, health, and material science applications. High Temperature Superconducting (HTS) conductors can develop a quench, i.e., localized hot spots due to a variety of physical phenomena causing the conductor to go resistive likely causing burnout and damaging the high-value high-field magnet. This research will provide a reliable cost-effective method for preventing HTS magnet quench. The fundamental idea is to Detect and Protect: Detect the incipient quench and Protect the HTS magnet through re-balancing the internal currents. The specific objectives are to identify, design, fabricate, and demonstrate advanced active cryogenic solid-state current-modulators for use in HTS magnets to prevent quenching. A digitally-controlled high current cryogenic driver for control of HTS cable component currents will be developed and demonstrated for use in HTS magnets to prevent quenching. This will also provide the opportunity to increase the maximum HTS magnet current-carrying capability and thereby increase magnet performance. Control circuity to operate multiple parallel FET devices independently with digital input will be designed, fabricated, and tested at cryogenic temperatures. Current steering utilizing solid-state devices will be demonstrated by independently controlling arrays of FET devices along a pair of HTS cables at 5 to 77 K. In addition, cryogenic current control for a small HTS coil will be implemented and demonstrated. High-field magnets have opened up accelerator capabilities for advancements in various physics, health, and material science applications. As stated in the recent P5 Report, the development of very-high-field magnets beyond the present state of the art is crucial for advanced colliders, and “high-temperature superconductors suitable for high field and temperature—are essential to this effort.” It was also stated that HTS materials, operated at temperatures greater than superfluid or liquid helium temperatures, can play a key role in the sustainability of future particle accelerators by significantly reducing their energy consumption. Quench protection methods for reliable, stable operation of these high-field HTS magnets are still under development, thus presenting good commercialization opportunities for this program.