Figure 9
The magnets system. The HTS magnets are installed in a SN2 chamber. Vacuum interlayer significantly reduces convective heat load from room temperature. Radiative heat load is reduced to 1/16 of its original level by 15 layers of radiation screens wrapping outside the SN2 chamber. Conductive heat load is minimized by hollow epoxy resin G10 bars with low thermal conductivity of 0.2 W/mK @ 30 K and 0.7 W/mK @ 300 K37. Access tubes made by bellows are used to suppress conductive heat load by increasing length of heat pathway. The SN2 chamber and its flange are all made of aluminum alloy (Al 6063-T5) for three reasons: (1) avoidance of unexpected leakage at cryogenic temperature due to different thermal expansion coefficients of dissimilar materials18, (2) ~1/3 mass density that of copper, and (3) good thermal conductivity (~250 W/mK @ 30 K) for direct connecting to a cryocooler. Besides, the current leads and the cryocooler are detached automatically by two nudgers when energizing process finishes.
