AC losses of Rutherford-type superconducting cables

Dipole magnets for hadron accelerators have shown quite different di/dt dependences in quench currents, even though they were made with similar Rutherford-type cables. Usually those accelerator magnets have been fabricated by curing the coils at higher temperature under mechanical pressure. Therefore, it is believed that this is mainly due to a variation of the interstrand coupling loss in the cables. The increase of the eddy currents in the cable conductors leads to a degradation of the magnet performance and changes for the worse magnetic field harmonics as well as an increase in the cryogenic heat load. As the nominal ramp rates of the dipole magnets become higher and higher, this problem becomes serious. Many authors have studied the AC losses of Rutherford-type cables having different soldering or coating materials, or different surface conditions. However, the reason why interstrand coupling loss in cabled conductors with bare strands varies over a wide range still remains unclear. AC loss measurements of Rutherford-type cables have been performed to investigate the factors which affect the interstrand coupling loss in more detail. This paper describes the experimental results of the AC losses, especially the interstrand coupling loss