強制冷却超電導コイルにおける安定性劣化と常電導伝播特性

Abstract

Typical forced flow cooled superconductor has a lot of strands in a conduit. It is pointed out, however, that there could be a non uniform current distribution in those strands because of the difference of inductance of each strand and/or the difference of contact resistance at terminals. This non uniform current distribution affects and greatly reduces the conductor's stability margin. We discuss the stability degradation and quench characteristics of a forced flow cooled superconducting coil that we have made. The conductor has 54 strands. Each strand has formvar insulation layer and electrically insulated each other. We have measured the stability margin of the test coil and characteristics of normal zone propagation and pressure rise during quench. We analyze these characteristics using numerical simulation code. It can simulate stability degradation, if we take non uniform current distribution into account. An additionl heat input, however, has to be taken into account to simulate quench characteristics in the simulations. This additional heat input is thought to be the heating caused by the heat diffusion between turns through the bobbin.