Beta limits in H-mode-like discharges
Recent tokamak beta optimization studies have indicated the existence of a \(\beta\) limit proportional to the plasma current. A two-step numerical optimization procedure is described for finding \(\beta\) limits in tokamak configurations with peaked current and flat pressure profiles, such as are believed to be characteristic of H-mode plasmas immediately after the L to H transition. Current and pressure-driven instabilities are optimized independently by specifying both the averaged current density and the pressure gradient directly. Direct control over both the global and local characteristics of the pressure profile also permits independent optimization of ballooning modes and the low n kink modes that arise at high \(\beta\). Results are given for the optimization of a circular cross-section tokamak, computed for one value of the plasma current. An optimized, stable equilibrium is found.
two-step numerical optimization procedure
scientific article; zbMATH DE number 3993156