Effect of a heat exchange between turns of a winding pack on cool down mode of forced-cooled S/C magnets [for ITER]

Results of thermal and stress analysis show that the cool-down scenario with linear helium inlet temperature decrease rate of 2 K/hour is believed to be realistic for the ITER (International Thermonuclear Experimental Reactor) magnet system. Under this helium inlet condition the coil cool-down time can be reduced to 150 hours. The equivalent stress in the TFC (toroidal field coil) case and in the superconductor´s jacket does not exceed allowable stress for the steel used. As for the electrical insulation of the winding pack, glass-fiber-reinforced epoxy can be used on the condition that its allowable stress normal to the laminae direction is not less than 140 MPa. According to the thermal analysis, the heat exchange between the winding pack turns and pancakes can strongly affect the coil cool-down only for the magnet with both layers of the double pancakes connected in series