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 τ_E,L is the L-mode confinement time and C_op 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 γ_H 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.