A control method of divertor plasma start-up assisted by tritium-ratio control for Demo-CREST

In this paper, core plasma operation flexibility by the tritium-ratio(T-ratio) control is proposed in order to control the fusion power keeping a high plasma density for the divetor heat-handling during the commissioning phase. The operational space of the core plasma for the Demo-CREST concept is expanded to the high density region by reducing T-ratio. Especially, the expansion of operation space for the low beta operation is large. For such operation expansion, the critical parameter is the confinement improvement factor HH, and a high HH similar to that of the ITER steady state (ITER-SS) operation is required for Demo-CREST. The resultant condition of the SOL density and the impurity radiation power required for the divertor heat load less than 10 MW/m² is analyzed, and those operation conditions for the initial operation point of the fusion power 0 MW during the commissioning phase are found to be similar to those of the ITER-SS operation.