Robust Control of Resistive Wall Mode in DIII-D Based on Eigenmode Approach
J. Dalessio, E. Schuster, M. Walker, D. Humphreys, Y. In, J-S. Kim
Division of Plasma Physics (DPP) Annual Meeting of the American Physical Society (APS)
Orlando, Florida, November 12-16, 2007
Abstract
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Control of the resistive wall mode (RWM) is a major focus of the
DIII-D experimental program. The FAR-TECH DIII-D/RWM model represents
the plasma surface as a toroidal current sheet and represents the wall
using an eigenmode approach [1]. The magnitude and phase of the RWM
plasma deformation is determined from a set of 22 poloidal field probes
and saddle loops, and 12 in-vessel coils are used to oppose the
deformation. The resulting model is reformulated into a robust control
framework, with a parameter that maps to the growth rate of the system
modeled as an uncertain parameter. A robust controller that stabilizes
the system for a range of practical growth rates is proposed, tested
through simulations, and compared to other control techniques.
Implications for experimental implementation and use are discussed.
[1] Y. In, et al., Phys. Plasma 13, 062512 (2006).