Model experiments to the conductivity of turn insulation of large fusion magnets during unmitigated quench

Abstract

The ITER superconducting magnet system stores a significant amount of energy. During an unmitigated quench, the undissipated energy can cause localized conductors to melt and break, leading to the formation of arcs. These arcs not only directly damage the conductor but may also cause indirect damage to adjacent components, such as the vacuum vessel and cryostat, potentially leading to the release of radioactivity. As the arcs form and develop in the magnet, the turn insulation gradually carbonizes. If the resistivity of the carbonized insulation is sufficiently low, it can affect the current distribution and arc propagation. To understand the conductivity of the turn insulation in a superconducting magnet during an unmitigated quench, this paper references the ITER magnet design and manufactures simplified samples. The experimental setup was established, and the samples were heated under a direct current. The voltage and temperature signals of the samples were analyzed during testing to gain a preliminary understanding of the turn insulation's conductivity from room temperature to 1000 °C over a heating period of several hundred seconds.