A hybrid heating method for the HT-7U coils during vacuum-pressure impregnation

The HT-7U superconducting tokamak is a full-superconducting magnetically confined fusion device. The toroidal magnet system of HT-7U is a very important part of the device. In VPI (Vacuum-Pressure Impregnation) process the magnet coils must be heated and degassed before impregnating and must be heated to the gel temperature and then the curing temperature, and keep the two kinds of temperatures for a long period of time after impregnating. Thus the heating method of VPI is critical. A hybrid method of combining the internal and external heating for the coils is analyzed, especially the possibility of the internal heating method is proved