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

摘要

A major concern in fusion reactor studies is to calculate the confinementenhancement factor, relative to L-mode scaling, required for reaching ignition. An ignition access condition is proposed, based on the generalized saddle point for the confinement scaling law. The concept of the operation path of a reactor is described as given by a generalized global power balance equation. The ignition access condition is then derived. The height of the generalized saddle point is calculated for various plasma parameters, and the height of the operation paths for next-generation tokamaks and a stellarator reactor are presented. The confinement enhancement factors required to reach ignition in these machines are obtained using the ignition access condition previously derived. The operation path method using the generalized ignition contour map is compared to the conventional POPCON method, and their relationship and respective advantages are discussed. It is shown that a confinement enhancement factor up to about 2.5 is needed to reach ignition in the machines considered.