Many high-temperature superconductor (HTS) applications require superconducting cables with high currents while operating in an alternating magnetic field. HTS cables should be composed of numerous superconducting tapes to achieve the required current capacity. Alternating current and magnetic fields cause AC losses in such cables and can provoke conductor instability. AC losses and contact resistances were measured of several cable designs based on commercially available REBCO tapes at the University of Twente. The AC loss was measured under identical conditions for eight REBCO conductors manufactured according to three types of cabling methods-CORC (R) (Conductor on Round Core), Roebel, and stacked tape, including a full-size REBCO CICC (cable in conduit conductor). The measurements were done at T = 4.2 K without transport current in a sinusoidal AC magnetic field of 0.4 T amplitude and frequencies from 5 to 55 mHz. The AC loss was measured simultaneously by calibrated gas flow calorimeter utilizing the helium boil-off method and by the magnetization method using pick-up coils. Also, the AC loss of two CORC (R) conductors and a Roebel cable was measured at 77 K. Each conductor was measured with and without background field of 1 T. The measured AC coupling loss in the CORC (R) and Roebel conductors is negligible at 4.2 K for the applied conditions while at 77 K coupling loss was observed for all conductors. The absence of coupling loss at 4.2 K can be explained by shielding of the conductor interior; this is confirmed with measurement and calculation of the penetration field of CORC (R) and Roebel cables. The inter-tape contact resistance was measured for CORC (R) and stacked tape samples at 4.2 and 77 K. It was demonstrated that a short heat treatment of CORC (R) conductor with solder-coated tapes activates tape-to-tape soldering and decreases the contact resistance. The reduction of contact resistance by two orders in magnitude to tens of nOm is comparable with the interstrand contact resistance in ITER Nb3Sn type conductors.

中文翻译：

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REBCO CORC®、Roebel 和叠层带状电缆中的交流损耗和接触电阻

许多高温超导体 (HTS) 应用需要在交变磁场中运行时具有高电流的超导电缆。HTS 电缆应由许多超导带组成，以达到所需的电流容量。交流电和磁场会导致此类电缆的交流损耗，并可能导致导体不稳定。交流损耗和接触电阻是在特温特大学根据商用 REBCO 胶带测量的几种电缆设计。在相同条件下测量了八根 REBCO 导体的交流损耗，这些导体根据三种类型的布线方法——CORC (R)（圆芯导体）、Roebel 和堆叠胶带，包括全尺寸 REBCO CICC（导管导体中的电缆） ）。测量是在 T = 4 时进行的。在 0.4 T 振幅和 5 至 55 mHz 频率的正弦交流磁场中，2 K 无传输电流。交流损耗通过使用氦蒸发法的校准气流热量计和使用拾波线圈的磁化法同时测量。此外，在 77 K 下测量了两个 CORC (R) 导体和 Roebel 电缆的 AC 损耗。在有和没有 1 T 背景场的情况下测量每个导体。 CORC (R) 和 Roebel 导体中测量的 AC 耦合损耗为对于应用条件，在 4.2 K 下可以忽略不计，而在 77 K 下观察到所有导体的耦合损耗。4.2 K 时没有耦合损耗可以通过导体内部的屏蔽来解释；对 CORC (R) 和 Roebel 电缆的穿透场的测量和计算证实了这一点。在 4.2 和 77 K 下测量 CORC (R) 和堆叠带样品的带间接触电阻。 结果表明，对带有焊料涂层的带的 CORC (R) 导体进行短时间热处理会激活带对带焊接和降低接触电阻。接触电阻降低两个数量级至数十 nOm，与 ITER Nb3Sn 型导体的线间接触电阻相当。