Active Feedback Control of Global Turbulence with Multiple Localized Controllers

The CTX device is a laboratory magnetosphere confining low density, interchange unstable plasmas which exhibit fully developed turbulent dynamics. A feedback system designed to measure potential fluctuations and apply a variably phase shifted response has been found to amplify or suppress this turbulence. Through multiple azimuthal measurements of floating potential, we see that the influence of the feedback system is localized, amplifying feedback having a larger spatial extend than suppressive. By installing another identical and independent feedback system 180 degrees from the first, we have significantly enhanced global suppression of turbulence. We also discuss the adaptations to previous work on a high performance simulation which evolves the coupled nonlinear PDEs that model (i) the gyro-kinetic electrons, (ii) cold fluid ions and, (iii) the time rate of change of the potential associated with interchange fluctuations. By including a representation of the feedback system in this simulation we hope to see a response similar to that measured experimentally.