HBT-EP Active MHD Mode Control Research
Author: David A. Maurer
Submitted: 2005-12-21 15:51:05
Co-authors: J. HANSON, A. KLEIN, Y. LIU, M.E. MAUEL, G.A. NAVRATIL, T.S. PEDERSEN, N. STILLITS, J. BIALEK, A.H. BOOZER, O. KATSURO-HOPKINS, D. MASLOVSKY, S.F. PAUL, R. JAMES
500 W120th St Rm. 201
New York, NY 10027
The HBT-EP active MHD mode control program is studying advanced feedback control algorithms, ITER relevant internal feedback control coil configurations, and simultaneous control of internal and external MHD modes relevant to innovative magnetic confinement concepts . The HBT-EP approach incorporates a segmented adjustable conducting wall, internal modular feedback control coils driven by a high-speed (10 microsec delay) MIMO digital control system for resistive wall modes (RWM), and edge rotation control using a biased electrode with supersonic nozzle fueling and lithium wall coating. Primary research thrusts are: (i) systematically study required feedback system gain as a function of control coil modularity and toroidal angle coverage compared with VALEN model predictions testing possible breakdown in basic rigid mode model; (ii) test advanced feedback control techniques of adaptive filtering and equilibrium state estimation; (iii) study physics of RWM rotation stabilization by controlled variation of critical parameters (rotation, dissipation, and growth rate) using biased electrode ExB flow and control of ion charge exchange viscosity; (iv) use improved understanding and control capability to suppress tearing and kink type MHD modes simultaneously near the ideal wall limit. We present results from discharges near the ideal wall limit involving poloidal sensors and control coils that directly face the plasma. Clear suppression of the external 3/1 kink mode has been achieved [1,2]. The effects of transfer function phase shift, loop latency, and control coil coverage have been investigated. Using both new internal Hall magnetic field measurements and external pick-up coil measurements we are able to derive the RWM and plasma mode eigenvectors describing the perturbed external fluxes. In discharges with RWM activity, the measured mode structure in the vacuum region is compared to model predictions using VALEN calculations of the effect of the passive wall and found consistent with Hall sensor array measurements. To aid in optimized feedback design and data analysis interpretation a method has been developed to extract the single circuit theory coupling constants directly from the VALEN inductance formalism. Comparison of these low dimensional models of kink mode dynamics will be discussed and compared to VALEN predictions and HBT-EP feedback and biased probe experiments.
 M. E. Mauel, et al., Nuc. Fusion, 45, 285 (2005).
 A. Klein, et al., Phys. Plasmas, 12, 40703 (2005).
 Y. Liu, et al., Rev. Sci. Inst. 76, 93501 (2005).
1 Supported by U. S. DOE Grant DE-FG02-86ER53222
Please place with other MHD control topical posters if possible.