Long lengths of metal/MgB2 composite conductors with high critical current density (Jc), fabricated by the power-in-tube (PIT) process, have recently become commercially available. Owing to its electromagnetic performance in the 20 K - 30 K range and relatively low cost, MgB2 may be attractive for a variety of applications. One of the key issues for magnet design is stability and quench protection, so the behavior of MgB2 wires and magnets must be understood before large systems can emerge. In this work, the stability and quench behavior of several conduction-cooled MgB2 wires are studied. Measurements of the minimum quench energy and normal zone propagation velocity are performed on short samples in a background magnetic field up to 3 T and on coils in self-field and the results are explained in terms of variations in the conductor architecture, electrical transport behavior, operating conditions (transport current and background magnetic field) and experimental setup (short sample vs small coil). Furthermore, one coil is quenched repeatedly with increasing hot-spot temperature until Jc is decreased. It is found that degradation during quenching correlates directly with temperature and not with peak voltage; a safe operating temperature limit of 260 K at the surface is identified.

中文翻译：

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传导冷却的 MgB2 导线和线圈的磁场相关稳定性和失超行为和退化限制

通过管内电源 (PIT) 工艺制造的具有高临界电流密度 (Jc) 的长金属/MgB2 复合导体最近已上市。由于其在 20 K - 30 K 范围内的电磁性能和相对较低的成本，MgB2 可能对各种应用具有吸引力。磁体设计的关键问题之一是稳定性和失超保护，因此在大型系统出现之前，必须了解 MgB2 导线和磁体的行为。在这项工作中，研究了几种传导冷却的 MgB2 线的稳定性和淬火行为。最小失超能量和法向区传播速度的测量在高达 3 T 的背景磁场中的短样品和自场中的线圈上进行，结果根据导体结构的变化进行解释，电传输行为、操作条件（传输电流和背景磁场）和实验设置（短样品与小线圈）。此外，一个线圈随着热点温度的升高而反复淬火，直到 Jc 降低。发现淬火过程中的退化与温度直接相关，与峰值电压无关；确定了表面 260 K 的安全工作温度极限。