Designing defect-tolerant high-temperature superconductor magnets

Richard Ibekwe


Tuesday, November 8, 2022



PSFC Student Seminars

High-temperature superconductor (HTS) magnets will enable net energy production from a new generation of high-field, compact fusion energy devices. Superconducting defects, however, whether intrinsic to HTS production or sustained during magnet fabrication or operation, will generate internal heat, reduce performance, and may ultimately lead to damage or failure. While the physical and operational characteristics of HTS offer high tolerance to defects, a rigorous physical understanding and quantification at relevant scale has not been established. To begin addressing this shortcoming, we present results from experiments with a copper cable containing a soldered stack of five HTS tapes and a physical defect. The cable enables electric field measurements with a high density array of voltage taps and current distribution measurements with 5 small embedded Rogowski coils. Measurements from a 2-mm defect in the central tape show significant defect-induced electric field disturbances compared to the non-defect case with characteristic decay lengths of approx. 50 mm, in rough agreement with modeling. Absolute current measurements along each tape will also be presented, which will show the effect of electric fields, geometry and electrical properties of HTS cables on current distribution. Such small-scale experiments will be used to develop and validate modeling that can scale to simulate full-scale magnets containing defects, enabling the identification of the physics, engineering and operational dependencies required to maximize defect tolerance.