Thermal Conductivity of NI HTS Coil Fabricated by Diffusion Bonding Technique

The no-insulation (NI) winding technique shows superior thermal protection performance when quenching of a high- temperature superconducting (HTS) coil occurs compared to the insulation winding technique. However, the thermal conductivity of an NI HTS coil are not clearly known because the HTS tape has various surface conditions such as roughness and oxidation. In this study, the diffusion bonding technique was applied to predict the thermal conductivity of an NI HTS coil, and the core of this technique is to remove the interface between turns by applying Ag diffusion bonding. To investigate the thermal conductivity of an NI HTS coil, an NI HTS coil was fabricated using a diffusion bonding technique, and a stainless-steel 304 block was fabricated to verify the experimental results. The thermal conductivity of the NI coil was measured using a conduction cooling experimental apparatus by applying heat loads to the outside of the coil. The measured thermal conductivity was compared to the values calculated using the thermal resistance circuit at temperatures from 20 K to 77 K.