Dong Fangliang, Park Dongkeun, Kim Junseong, Bascuñán Juan, Iwasa Yukikazu
All of the authors are with the Francis Bitter Magnet Laboratory/Plasma Science and Fusion Center, Massachusetts Institute of Technology, Cambridge, MA 02139, USA.
IEEE Trans Appl Supercond. 2023 Aug;33(5). doi: 10.1109/tasc.2023.3238987. Epub 2023 Jan 23.
It is generally agreed that no-insulation (NI) high-temperature superconducting (HTS) magnets do not quench because of the turn-to-turn energy-releasing bypass unique to NI. However, these magnets, especially with high operating current and low ambient thermal capacity, still occur unexpected quenches when the current through the magnets suddenly drops to zero (i.e., the sudden-discharging quench). Here, we report this kind of quench, which is different from that widely-reported quench happening during charging (i.e., the energizing quench). Here, a demonstrative coil with 655-turns, 350 A operating current, and 4 K conduction cooling, is used to prove this sudden-discharging quench, and a simulation model is built to reveal the quench dynamics. Results show the turn-to-turn heat triggers the initial partial quench in the inner coil turns and then the induced overcurrent spreads out the quench like an avalanche to the outer coil turns.
人们普遍认为，无绝缘（NI）高温超导（HTS）磁体不会因NI特有的匝间能量释放旁路而失超。然而，这些磁体，特别是在高工作电流和低环境热容量的情况下，当通过磁体的电流突然降至零（即突然放电失超）时，仍会发生意外失超。在此，我们报告这种失超情况，它不同于充电过程中广泛报道的失超（即通电失超）。这里，使用一个具有655匝、350 A工作电流和4 K传导冷却的示范线圈来证明这种突然放电失超，并建立了一个模拟模型来揭示失超动态过程。结果表明，匝间热触发了内线圈匝中的初始局部失超，然后感应过电流像雪崩一样将失超扩展到外线圈匝。
