Ignition Access Condition Based on the Generalized Saddle Point in a Magnetic Fusion Reactor

The ignition access condition is described based on the operation path and the saddle point in the generalized ignition contour map . With a confinement scaling law such as for the energy confinement time in terms of the net input heating power density, as employed in most Plasma Operation Parameter Contour (POPCON) analyses, where τE,L is the L-mode confinement time and Cop is the constant parameter, the ignition access condition is given by , where is the height of the generalized saddle point. The height of the generalized saddle point for various arbitrary plasma parameters enables a reactor designer to look at the overall behavior of a reactor. The confinement enhancement factor γH is determined relative to the L mode, which is required for reaching ignition in a tokamak or stellarator reactor. This operation path method is compared with the POPCON approach, and the relative merits of each are discussed.