Comparative studies of the dW/dt effect in the net heating power for ignition analyses

Abstract We compare two cases with and without subtraction of d W /d t in the net heating power after the high confinement mode transition (H-transition) and study the effects of d W /d t on zero-dimensional ignition analyses in various ignition phases in a deuterium–tririum (D–T) tokamak reactor including International Thermonuclear Experimental Reactor (ITER). Subtraction of d W /d t from the net heating power after the H-transition as done in H-mode power threshold analyses results in a wrong control action in feedback control during the confinement factor increment and abnormal behaviors in operation phases such as fusion power ramp-up, steady state, and shutdown phases in a reactor. As subtraction of dW/dt in the L-mode phase is to describe the delay time effect of the heating power to the plasma edge, we conclude that d W /d t should not be subtracted from the net heating power after the H-transition in the zero-dimensional approach. This is because that the H-mode is determined by the net heating power to the plasma edge both before and after the H-transition, but not by the plasma conduction loss power out of the plasma edge.