Feasibility study of large-scale superconducting magnets without layer-to-layer insulation.

首先，提出了以支撑结构作为保护电阻的超导磁体的概念设计。其次，对原理论证用小线圈样机的设计进行了修改。根据对用于聚变反应堆的磁体的基本规格的审查结果，可以理解，为了在常规制冷功率范围内减少励磁过程中的热产生，磁体的匝间电阻必须达到数十μΩ或更高。这意味着只有不锈钢才能承受的阻力太小。如果电阻过大，则关闭电压超过允许值。因此，我们需要比不锈钢高1000到100,000倍的导电材料。对这种材料进行了研究，并制备了导电陶瓷和导电树脂。虽然导电陶瓷可以作为真正的磁体的候选者，但从生产率和易得性的角度考虑，选择含碳的导电树脂作为样品。用该树脂制作了无层间绝缘的线圈样品，由于需要较大的磁能来保证失超保护，因此选择了直径约100 mm的螺线管线圈。采用了200 A矩形截面的NbTi钢绞线。它的铜比为3。线圈是池冷的，其绕组与周围的氦气绝缘，以评估关闭时的温升。然后线轴由纤维增强塑料制成，绕组的外部用Kapton胶带包裹。层之间的电阻可以通过调整裸露的NbTi股之间的间距和将导电树脂摩擦到空间中来控制。虽然改进缠绕方法以保证一定的层间距，但证明了导电树脂的可行性。

At first, the conceptual design of the superconducting magnet in which the supporting structure was used as a protection resistance was advanced. Secondly, the design of the small coil sample for the principle proof was revised. As the results of the examination of a basic specification of the magnet used for the fusion reactor, it was understood that the resistance of tens of μ Ω or more was necessary for the resistance between turns of the magnet to reduce the heat generation during the excitation within the conventional refrigerating power. It means that the resistance only by stainless steels is too small for it. If the resistance is too large oppositely, the shut-off voltage exceeds the allowable value. Therefore, we need the conductive material that has 1, 000 to 100, 0000 times higher resistivity than stainless steels. Such a material was investigated, and conductive ceramics and the conductive resin were made candidates. Although the conductive ceramics can be a candidate for the real magnet, the conductive resin with carbon is selected for the sample from a viewpoint of productivity and easiness of obtaining. A coil sample without the layer-to-layer insulation was produced with the resin.Since the larger magnetic energy is preferred to prove the quench protection, the solenoid coil with the diameter of about 100mm was selected. The NbTi strands class 200 A in a rectangular section was used. Its copper ratio is three. The coil is pool-cooled, and its winding is insulated from surrounding helium to evaluate the temperature rise when shut-off. Then the bobbin is made of fiber reinforced plastics, and the outside of the winding is wrapped with Kapton tapes. The resistance between layers can be controlled by adjusting the spaces between the bare NbTi strands and by rubbing the conductive resin into the space. Although the winding method to secure the certain space between layers should be improved, the feasibility of the conductive resin was proved.