An investigation of A.C. losses in two sub-size conductors for the ITER

Two second sub-size CiC conductors manufactured as models for the full-size conductors to be used in the poloidal coils of the ITER tokamak machine were tested to determine their A.C. loss characteristics. One conductor was manufactured by Furukawa (a 3x4x4 strand conductor), the other by Hitachi Cable (3x3x3). Each sub-size conductor sample, wound in a solenoid, was tested in a background magnet with zero transport current. For a single cycle ramp-up from 0 T to 1.15 T and then back to zero, hysteresis loss for the Furukawa conductor was 12.6 mJ per cubic centimeter of conductor volume (not including conduit), while the hysteresis loss for the Hitachi Cable sample was 19.9 mJ/cc. Each sample was then forced to experience an exponential decay of the background field, using different decay time constants for each trial, and the coupling loss was subsequently plotted versus the inverse of the background field decay. A 'best-estimate' value for the coupling time constant for each sample was determined based on theory; the Furukawa sample had a coupling time constant of about 27(±5) ms, while the Hitachi Cable sample had a coupling time constant of about 11(±5) ms. (author)