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Sharp-Boundary Non-Ideal Plasma Response Model with a Ferritic-Resistive Wall

Author: Dov J. Rhodes
Requested Type: Poster Only
Submitted: 2015-01-15 13:30:48

Co-authors: A.J. Cole, G.A. Navratil, R. Fitzpatrick

Contact Info:
Columbia University
500 W. 120th St.
New York, NY.   10027
United States

Abstract Text:
A fast, semi-analytical approach is presented for calculating the error-field response of a plasma surrounded by an ITER-like ferritic-resistive wall, based on a recent model by Fitzpatrick [1]. The approach is based on the sharp-boundary, high aspect-ratio model pioneered by Freidberg [2], for solving the free-boundary ideal MHD stability problem. Fitzpatrick introduced dissipative rational surfaces and strongly shaped geometry to study the mode-coupled plasma response and resultant error-field torque.
The present work extends the model to include a ferritic-resistive thin wall concentric to the plasma, and up-down asymmetric geometry (i.e. single-null diverted plasmas). Two key results are presented. First, a poloidal mode-coupled dispersion relation for the resistive wall mode (RWM) growth rate is derived. Secondly, the mode-coupled plasma response to an error-field applied outside the ferritic-resistive thin wall is presented.
The aim of the model is to facilitate a rapid exploration of the parameter space for the response of a non-ideal shaped plasma to error-fields. This will enable efficient calculations to complement larger codes such as NIMROD and PEST3. Better understanding of the multi-mode plasma response to error-fields will facilitate more effective design of feedback control systems in a tokamak. A specific future application is the toroidal extension of a recent cylindrical resistive plasma, resistive wall control theory [3]. Finally, the shaped plasma response model is formulated to provide input for the VALEN code [4], which calculates RWM stability in the presence of precise 3D wall structure. References: [1] R. Fitzpatrick, Phys. Plasmas 17, 112502 (2010). [2] J.P. Freidberg and F.A. Haas, Phys. Fluids 17, 440 (1974). [3] D. P. Brennan and J. M. Finn, Phys. Plasmas 21, 102507 (2014). [4] J. Bialek et al., Phys. Plasmas 8, 2170 (2001). Supported by U.S. DOE Grant DE-FG02-86ER53222.
R. Fitzpatrick affiliation: University of Texas at Austin

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