Robust Control of Resistive Wall Modes in Tokamak Plasmas using \mu-synthesis

J. Dalessio, E. Schuster, D.A. Humphreys, M.L.Walker, Y. In, and J.S. Kim

IFAC World Congress on Automatic Control

Seoul, Korea, July 6-11, 2008

Abstract

In this work, \mu-synthesis is employed to stabilize a model of the resistive wall mode (RWM) instability in the DIII-D tokamak. The GA/Far-Tech DIII-D RWM model is used to derive a linear state space representation of the mode dynamics. The key term in the model characterizing the magnitude of the instability is the time-varying uncertain parameter cpp, which is related to the RWM growth rate gamma. Taking advantage of the structure of the state matrices, the model is reformulated into a robust control framework, with the growth rate of the RWM modeled as an uncertain parameter. A robust controller that stabilizes the system for a range of practical growth rates is proposed and tested through simulations.