Comparison of Effective Thermal Conductivity in Radial Direction of No-Insulation, Metal-Insulation and Kapton Insulation HTS Coil

The effective thermal conductivity of a high temperature superconductor (HTS) coil is an important parameter controlling the temperature of the coil in normal and off-normal operation. It is also a highly anisotropic parameter. While the thermal conductivity along the length is easily derived from the constituent materials, the radial direction thermal conductivity depends strongly on the fabrication method and surface conditions of the conductor. In this paper, three HTS coils are fabricated with insulation, no-insulation, and metal insulation winding schemes to evaluate the thermal conductivity in the radial direction, on a same winding form with a same winding tension. The thermal conductivity is measured by temperature difference in a conduction cooled experimental apparatus while applying heating to the outer surface of the HTS coils. The experiments are conducted by controlling the temperature from 20 K to 70 K. The measured effective thermal conductivity will be used to estimate the temperature distribution in the coil during charging/discharging operation and in the event of a quench.