Fluctuation mitigation and azimuthal velocity profile regulation by extremum seeking in HELCAT

Turbulence, and turbulence-driven transport are ubiquitous in magnetically confined plasmas, where there is an intimate relationship between turbulence, transport, destabilizing mechanisms like gradients and currents, and stabilizing mechanisms like shear. Active control of fluctuations via manipulation of flow profiles is investigated in a magnetized laboratory plasma device (HELCAT). Measurements of the azimuthal velocity are assumed available at several radial points within the plasma and E × B flow profiles are controlled via biased ring electrodes. An optimal control algorithm is proposed in this work to reproduce as closely as possible a prescribed desired radial azimuthal velocity profile. The effectiveness of the controller is analyzed via numerical simulations.