C J Ham et al 2009 Plasma Phys. Control. Fusion 51 115010 doi:10.1088/0741-3335/51/11/115010
C J Ham, C G Gimblett and R J Hastie
Show affiliationsFusion power from a tokamak increases as β2 (β is the ratio of the plasma and magnetic field pressures) and so the mitigation of instabilities such as the resistive wall mode (RWM), that can prevent high β operation, is important. Stabilization of the RWM with a plasma rotation frequency of below 1% ΩA, where ΩA is the Alfvénic rotation frequency, has been observed in a number of tokamaks. An analytical model for this stabilization, in a cylindrical plasma with a resonant layer, is discussed here. The layer theory of Porcelli (1987 Phys. Fluids 30 1734) is used to provide a model of the physics within the resonant layer. A dispersion relation connecting the plasma equilibrium to the layer physics in a rotating plasma is developed. Two mechanisms for RWM stabilization are investigated. The first includes viscosity in the resonant layer. The second assumes that stabilization occurs in the transition from one layer response to another. These models indicate a priori that there is a large parameter space where stabilization of the RWM by rotation is possible. However, if experimentally realistic timescales and rotation, namely O(1)% ΩA, are considered then only a small window for stabilization exists. It is therefore unlikely that these mechanisms explain the observed experimental RWM stabilization. It seems that other physical effects, such as toroidal mode coupling in the outer equilibrium or pressure gradients in a toroidal geometry, will be responsible for stabilization.
52.55.Fa Tokamaks, spherical tokamaks
52.30.Cv Magnetohydrodynamics (including electron magnetohydrodynamics)
52.40.Hf Plasma-material interactions; boundary layer effects
Issue 11 (November 2009)
Received 2 June 2009, in final form 17 September 2009
Published 28 October 2009
C J Ham et al 2009 Plasma Phys. Control. Fusion 51 115010
Liu-Gang Si et al 2009 J. Phys. B: At. Mol. Opt. Phys. 42 225405
Huang Lingxiong et al 2009 J. Phys. D: Appl. Phys. 42 225109
Olga Russina et al 2009 J. Phys.: Condens. Matter 21 424121
Fèlix Casanova et al 2008 Nanotechnology 19 315709
Ning Wu et al 2009 J. Phys.: Condens. Matter 21 474222
G Sreekumar et al 2009 J. Opt. A: Pure Appl. Opt. 11 125204
Yong Jiang et al 2009 J. Phys.: Conf. Ser. 190 012106
Ana-Maria Popa et al 2009 Nanotechnology 20 485303
Christian F Ihle et al 2009 Meas. Sci. Technol. 20 125402