We present results—cool-down, energization, and persistent-mode operation—of a solid-nitrogen (SN2)-cooled, magnesium diboride (MgB 2 ) small-scale test coil. The test coil, immersed in a volume of solid nitrogen at 6 K, successfully operated in persistent-mode at 108 A for a period of 5 d. Although designated a ‘persistent-mode’ coil, its center field was measured to decay at a rate of <0.6 ppm h −1 , which is still considered low enough to meet the temporal stability requirement of <0.1 ppm h −1 , for most magnetic resonance imaging magnets. This decay rate translates to a calculated circuit resistance of <1.79 × 10 –12 Ω, which is mainly from one MgB 2 -MgB 2 joint in the circuit. However, when the coil temperature increased from 6 to 16 K, the field had dropped by 0.33%: we believe this was caused by the change of magnetization in the MgB 2 superconductor, which in turn decreased a screening-current f...

中文翻译：

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固氮冷却的MgB 2小型测试线圈对台式1.5-T骨质疏松MRI的持久模式操作和磁化行为

我们介绍了固态氮（SN2）冷却的二硼化镁（MgB 2）小型测试线圈的结果-冷却，通电和持久模式运行。将测试线圈浸入6 K的固态氮气中，以108 A的持续模式成功运行5 d。尽管被指定为“持久模式”线圈，但它的中心场被测量为以<0.6 ppm h -1的速率衰减，对于大多数情况，仍被认为足够低以满足<0.1 ppm h -1的时间稳定性要求。磁共振成像磁铁。该衰减率转换为计算得出的电路电阻<1.79×10 –12Ω，这主要来自电路中的一个MgB 2 -MgB 2接头。但是，当线圈温度从6 K升高到16 K时，磁场下降了0.33％：