Numerical optimization of actuator trajectories for ITER hybrid scenario profile evolution

TitleNumerical optimization of actuator trajectories for ITER hybrid scenario profile evolution
Publication TypeJournal Article
Year of Publication2014
AuthorsJ. van Dongen, F. Felici, G.MD Hogeweij, P. Geelen, E. Maljaars
JournalPlasma Physics and Controlled Fusion
ISBN Number0741-3335

Optimal actuator trajectories for an ITER hybrid scenario ramp-up are computed using a numerical optimization method. For both L-mode and H-mode scenarios, the time trajectory of plasma current, EC heating and current drive distribution is determined that minimizes a chosen cost function, while satisfying constraints. The cost function is formulated to reflect two desired properties of the plasma q profile at the end of the ramp-up. The first objective is to maximize the ITG turbulence threshold by maximizing the volume-averaged s / q ratio. The second objective is to achieve a stationary q profile by having a flat loop voltage profile. Actuator and physics-derived constraints are included, imposing limits on plasma current, ramp rates, internal inductance and q profile. This numerical method uses the fast control-oriented plasma profile evolution code RAPTOR, which is successfully benchmarked against more complete CRONOS simulations for L-mode and H-mode mode ITER hybrid scenarios. It is shown that the optimized trajectories computed using RAPTOR also result in an improved ramp-up scenario for CRONOS simulations using the same input trajectories. Furthermore, the optimal trajectories are shown to vary depending on the precise timing of the L–H transition.







Alternate TitlePlasma Phys. Control. Fusion

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