Development of conduction-cooled superconducting coils having good processing and high thermal conduction plastic bobbins

超导线圈的电阻在极低的温度下为零，因此超导线圈的冷却方法是浸泡在液氦等低温液体中。另一种冷却方法是通过冰箱传导冷却。由于超导线圈只能通过制冷机冷头的传导来冷却，从线圈稳定性的角度来看，结构材料的导热性能非常重要，因此我们提出了一种高导热塑料作为结构材料，命名为Dyneema纤维增强塑料(DFRP)。DFRP具有随温度降低而热膨胀的特点。制作了带有DFRP线轴的超导小线圈，并用制冷机进行了冷却，测量了线圈的稳定性。制作了与氮化铝和玻璃纤维增强塑料(GFRP)具有相同规格的线圈，并对其稳定性进行了对比测试，实验数据表明，在较大的线圈缠绕张力条件下，从线圈到结构材料的换热较好，而DFRP线圈的稳定性与AlN线圈的稳定性相当或更好。

Electric resistance of superconducting coils becomes zero at extremely low temperature, and hence cooling method of the coils is immersing in low-temperature liquids such as liquid helium. Another cooling method is conduction cooling by a refrigerator. Because the superconducting coil is cooled only by the conduction from a cold head of the refrigerator, thermal conductivity of structural materials is very important from a viewpoint of stability of the coil.We propose a high thermal conduction plastic as the structural material whose name is a Dyneema fiber reinforce plastic (DFRP). DFRP has a characteristic of thermal expansion with decreasing of temperature. The small superconducting coils with DFRP bobbins were made and cooled by a refrigerator, and the coil stability was measured. The coil having the same specifications that made of aluminum nitride and glass fiber reinforced plastic (GFRP) were also made and stability were measured for the comparison.According to the experimental data, the heat transfer from the winding to the structural material became good in the condition with large coil winding tension, and the DFRP coil stability is similar or better than the AlN coil stability.