Analyses of AC loss of pulsed superconducting magnet

A study is made to provide a practical method for analyzing the AC loss in a 0.5 pulsed superconducting magnet. The magnet field profile during pulse operation (5 - 10 T/s) and that during direct current application are compared experimentally to confirm that there are no large differences between them. Thus, the analysis is performed based on the magnetic field profile during DC drive. The superconducting wire examined is composed of a normal metal core (NC) surrounded by uniformly distibuted filaments (UF) and coated with CuNi. Analysis of the multifilament wire shows that for a magnetic field in the range of 5 - 10 T/s, the NC accounts for a great portion of the total coupling loss in the wire. Therefore, the coupling loss in the coil is calculated by integrating the coupling loss in the NC region in each part of the coil, while taking into account the magneto-resistance effect of copper making up the NC. The hysteresis loss in the filament is calculated by integrating the loss due to magnetic field components perpendicular to each part of the filament. The hysteresis loss due to magnetic field components parallel to the filament axis is ignored. It is revealed that AC loss calculated by the above procedure agrees well with experimental values deterined from evaporation of helium. (Nogami, K.)