Development of a forced-cooled superconducting coil for fusion applications

A test coil was wound from a NbTi cable-in-conduit type conductor with 54 strands, and the total conductor length was 36 m. It was force-cooled with supercritical helium. The critical current of the test coil was 3.5 kA at 7 T. The test coil was installed in a backup coil which generated the magnetic field up to 7 T. The experimental results from the propagation velocity of the normal zone and the pressure rise when the force-cooled superconducting coil is quenched are described. The results of an analysis of the stability margin of the coil using computer simulation are reported.<>