The ignition access and ignited operation regime are studied using a POPCON analysis with the H-mode power threshold scalings for a D - T experimental tokamak reactor, such as the International Thermonuclear Experimental Reactor (ITER). The H-mode power threshold scaling provides two H-mode regimes in the low-density and high-density regions. The L-mode regime exists between them. As the two H-mode regimes are connected at a plasma temperature around 30 keV, the operation path must make a detour around this connecting area to reach ignition within a reasonable heating power. Although the heating power to reach ignition depends on the coefficient in the H-mode power threshold scaling and plasma parameters, the heating power of 50 MW, as originally proposed by Rebut et al, is marginal and not sufficient to reach ignition for the ITER tokamak even if the L - H transition can be first achieved in the initially low-density regime of less than . Auxiliary heating power of 100 MW may satisfy the various requirements for D - T ignition experiments in the ITER tokamak. The thermal equilibrium operating point with fusion power of 1.5 GW in the ignition regime can exist only when the H-mode power threshold has a hysteresis for the ASDEX Upgrade threshold scaling.
Comparative studies of the dW/dt effect in the net heating power for ignition analyses