Fig. 6: Demonstration of increased robustness to control uncertainty.
From: Learning plasma dynamics and robust rampdown trajectories with predict-first experiments at TCV
a A comparison of a shot designed prior to adding control uncertainty, #81751, and after, #82875. We see that the vertical instability growth rate, γvgr, is highly sensitive to control error in the high-field side gap, gHFS,error, in #81751, but similar control errors experienced in #82875 result in negligible changes in stability. Time shown, trelative, is the time relative to 1.4 s for #81751 and 1.3 s for #82875 to align the moment the two shots experience similar control errors. Additional quantities shown are the plasma elongation κ, minor radius aminor, high-field side gap, gHFS, and low-field side gap, gLFS. b γvgr distributions under 1.5 cm of minor radius control error for #81751 and #82875. Control error was simulated by introducing variations in the control points provided to the free-boundary equilibrium solver, FBT69,75, used for shot preparation. The resulting equilibria were then input into the γvgr computation method used in this work40.
