A new winding method to reduce AC losses in stable LTS pulse coils

A new winding method was proposed to reduce ac losses in stable LTS pulse coils. The suitable conductor for this winding method is a multi-layer type conductor composed of stacked Rutherford type cables with low resistive contact between strands. In this winding method, the twist angle around, axis of the conductor is controlled during winding process to adjust the direction of edge-on orientation to stacked cables to direction of local magnetic fields applied to the conductor in winding areas. Inter-strand coupling losses in this coil are expected to be small in spite of low resistive contact between strands in the wound conductor. In order to clarify the effect of this winding method, firstly, a test conductor was fabricated and ac losses in short samples of the conductor were measured. This was an aluminum stabilized conductor, and a Rutherford cable composed of 8 Cu/Nb-Ti strands was used as the core of this conductor. The loss is measured with the transverse magnetic fields applied either perpendicular or parallel to the broad cable face, the "face-on"(FO) and "edge-on"(EO) orientations, respectively. From observed data, it is found that EO loss is 0.12 times FO loss. Secondly, ac losses in test coils wound with this conductor were calculated. The result showed that this winding method was very effective.