Heat Drain Effects From HTS Tapes to High Thermal Conduction Plastics for Conduction-Cooled Magnets

In conduction-cooled HTS magnets, it is important to design effective heat drains from the HTS tapes to a cold head of a refrigerator. Aluminum nitride (AlN) is often used as a heat-drain material because thermal conductivity and electric insulation of the material are good. However, the AlN is hard and brittle, and hence it is difficult for magnet makers and users to process the AlN. To address this issue, we have studied to use the plastic having both high-thermal conduction and high-electric insulation properties as the heat drain material. The plastic is the Dyneema fiber reinforced plastic (DFRP). We fabricated an experimental arrangement in which the Bi-2223 tape and the DFRP block were contacted, and a steady current was applied to the tape. Based on the measured voltage between terminals, thermal drain properties from the tape to the DFRP block were estimated. In the same conditions, experiments using the glass fiber reinforced plastic (GFRP) were also performed. Furthermore, the coil shape sample made of the AlN and DFRP were used. The paper presents the difference of the thermal drain performance in the AlN, the DFRP and the GFRP.