Experiments of the 1-m-bore, 30-kA superconducting demo poloidal coils

The first experiment on the Nb-Ti pulsed coils, DPC (demonstration poloidal coil)-U1 and -U2, was successfully performed. The coils have a cable-in-conduit conductor cooled by 4-K supercritical helium, and their windings have 1-m inner, and 2-m outer, diameters. Charging tests on the coils were performed in both DC and pulsed modes. In DC mode, the coils were charged individually to their design current of 30 kA, and attained a peak field of 5.2 T and a stored energy of 11 MJ. In pulsed mode, using the power supply of the JT-60, the designed pulsed field of 7 T/s were achieved by charging one of the two coils to its design current in 0.75 s. AC losses of the coil during the pulsed operation were confirmed to be quite small. Mechanical, thermal, and hydraulic properties were also analyzed on the basis of the experimental results