Dong Fangliang, Park Dongkeun, Kim Junseong, Bascuñán Juan, Iwasa Yukikazu
Francis Bitter Magnet Laboratory/Plasma Science and Fusion Center, Massachusetts Institute of Technology, Cambridge, MA 02139, USA.
Supercond Sci Technol. 2024 Nov;37(11). doi: 10.1088/1361-6668/ad826a. Epub 2024 Oct 11.
In this paper, we apply a surface-shunting method to prevent quenches in no-insulation (NI) REBCO magnets triggered by external failures of magnet current leads or power suppliers (i.e., fault mode). In a high-field magnet system, an NI coil may still be at risk during the mentioned quench events even if the whole magnet is well-designed, non-defective, and properly operated. The mechanism of this fault-mode quench initiation and propagation still remains unclear, complicating the development of reliable quench protection. Here, we present this mechanism to demonstrate a corresponding practical quench-preventive approach named surface shunting, which utilizes a low-temperature solder attached to the top and bottom of pancake coils. We validate the effectiveness of this approach by comparing the electromagnetic, thermal, and mechanical behaviors in the fault mode with and without the shunt. We conclude that the surface shunt suppresses the fault-mode quench initiation and propagation by redirecting the original turn-to-turn current and induced overcurrent out of the NI winding. We anticipate this work can provide a solution to improve the operational safety of high-field HTS NI magnets against quench and potential damage during fault modes.
在本文中，我们应用一种表面分流方法来防止无绝缘（NI）稀土钡铜氧（REBCO）磁体因磁体电流引线或电源的外部故障（即故障模式）引发的失超。在高场磁体系统中，即使整个磁体设计良好、无缺陷且运行正常，在上述失超事件期间，NI线圈仍可能面临风险。这种故障模式下失超的起始和传播机制仍不明确，这使得可靠的失超保护的开发变得复杂。在此，我们阐述这一机制，以展示一种名为表面分流的相应实用失超预防方法，该方法利用附着在饼式线圈顶部和底部的低温焊料。我们通过比较有分流和无分流情况下故障模式下的电磁、热和机械行为，验证了该方法的有效性。我们得出结论，表面分流通过将原有的匝间电流和感应过电流引出NI绕组，抑制了故障模式下失超的起始和传播。我们预计这项工作能够为提高高场高温超导NI磁体在故障模式下抵抗失超及潜在损坏的运行安全性提供一种解决方案。
