Control of Trapped Electron Instability by Modulated Neutral Beams.
Abstract
Feedback control of the Dissipative Trapped Electron Instability in tokamaks is investigated using a modulated neutral beam as a remote suppressor. Particle input from the beam is found to be the most effective control variable. Oblique injection is found to be the most suitable and the best angle of injection has been estimated from the control point of view. The evolution of control source ion distribution function in velocity and configuration space due to pitch angle scattering by collisions with plasma ions is determined by using a FokkerPlanck collision operator. This distribution function is used to find the density profile of the control source in plasma, also coupling of the modulated neutral beam to the instability. Modal decomposition of the instability is used in order to obtain a lumped parameter representation of the multimode instability. Optimal control theory is then applied to stabilize the instability by minimizing a performance index which is chosen to be the sum of residual fluctuation energy (from the instability) and control energy. As sensor signal is corrupted by noise, a Kalman filter is designed to estimate the states which are the complex modal amplitudes of the instability. The estimated states are then used in a state feedback scheme for optimal control. The level of control signal is estimated and is found to be easily obtainable from present day neutral beams.
 Publication:

Ph.D. Thesis
 Pub Date:
 1980
 Bibcode:
 1980PhDT........32G
 Keywords:

 Physics: Fluid and Plasma;
 Beam Injection;
 Feedback Control;
 Magnetohydrodynamic Stability;
 Neutral Beams;
 FokkerPlanck Equation;
 Ion Distribution;
 Kalman Filters;
 Optimal Control;
 Tokamak Devices;
 Trapped Particles;
 Plasma Physics