Effect of toroidal plasma flow and flow shear on global magnetohydrodynamic MHD modes

Chu, M. S.; Greene, J. M.; Jensen, T. H.; Miller, Robert L.; Bondeson, A.; Johnson, Robert W.; Mauel, M. E.

doi:10.1063/1.871247

Cited by 213 publications

(250 citation statements)

References 12 publications

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“…In contrast to previous studies [3,4], this complete stabilization is obtained without adding parallel damping to the ideal magnetohydrodynamic (MHD) model. Our approach couples the plasma, which has an equilibrium flow, to the resistive wall by using a Green's function, so that the vacuum region is not discretized.…”

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confidence: 90%

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Numerical calculations demonstrating complete stabilization of the ideal magnetohydrodynamic resistive wall mode by longitudinal flow

et al. 2009

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The cylindrical ideal magnetohydrodynamic (MHD) stability problem, including flow and a resistive wall, is cast in the standard mathematical form, ωA⋅x=B⋅x, without discretizing the vacuum regions surrounding the plasma. This is accomplished by means of a finite element expansion for the plasma perturbations, by coupling the plasma surface perturbations to the resistive wall using a Green’s function approach, and by expanding the unknown vector, x, to include the perturbed current in the resistive wall as an additional degree of freedom. The ideal MHD resistive wall mode (RWM) can be stabilized when the plasma has a uniform equilibrium flow such that the RWM frequency resonates with the plasma’s Doppler-shifted sound continuum modes. The resonance induces a singularity in the parallel component of the plasma perturbations, which must be adequately resolved. Complete stabilization within the ideal MHD model (i.e., without parallel damping being added) is achieved as the grid spacing in the region of the resonance is extrapolated to 0 step size.

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confidence: 90%

“…A proven method to stabilize the RWM is for the plasma to have equilibrium flow [1]. This method has also been explored theoretically [2] and numerically [3,4].…”

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confidence: 99%

Numerical calculations demonstrating complete stabilization of the ideal magnetohydrodynamic resistive wall mode by longitudinal flow

et al. 2009

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“…These discharges are calculated to be unstable to a resistive interchange and are also unstable to a double tearing mode in the absence of plasma rotation. The strong rotational shear stabilizes the double tearing, but bursts of MHD, localized in the negative shear region and possibly a resistive interchange reduces the rotational shear and may drive the double tearing unstable (Chu 1995(Chu , 1996Strait 1997).…”

Section: Ts Taylormentioning

confidence: 99%

Physics of advanced tokamaks

Taylor¹

1997

Plasma Phys. Control. Fusion

208

153

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Significant reductions in the size and cost of a fusion power plant core can be realized if simultaneous improvements in the energy replacement time, τ E , and the plasma pressure or beta, β T = 2 µ 0 P /B 2 can be achieved in steady-state conditions with high selfdriven, bootstrap current fraction. Significant recent progress has been made in experimentally achieving these high performance regimes and in developing a theoretical understanding of the underlying physics. Three operational scenarios have demonstrated potential for steadystate high performance, the radiative improved mode, the high internal inductance or high i scenario, and the negative central magnetic shear, NCS (or reversed shear) scenario. In a large number of tokamaks, reduced ion thermal transport to near neoclassical values, and reduced particle transport have been observed in the region of negative or very low magnetic shear: the transport reduction is consistent with stabilization of microturbulence by sheared E × B flow. There is strong temporal and spatial correlation between the increased sheared E × B flow, the reduction in the measured turbulence, and the reduction in transport. The DIII-D tokamak, the JET tokamak and the JT-60U tokamak have all observed significant increases in plasma performance in the NCS operational regime. Strong plasma shaping and broad pressure profiles, provided by the H-mode edge, allow high beta operation, consistent with theoretical predictions; and normalized beta values up to β T /(I /aB) ≡ β N ∼ 4.5% m T MA −1 simultaneously with confinement enhancement over L-mode scaling, H = τ/τ ITER-89P ∼ 4, have been achieved in the DIII-D tokamak. In the JT-60U tokamak, deuterium discharges with negative central magnetic shear have reached equivalent breakeven conditions, Q DT (equiv) = 1.

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“…In these experiments, there is a rapid toroidal rotation due to unbalanced neutral beam injection. Theoretically, it is shown that the combination of plasma rotation and some dissipation model can stabilize RWMs [4][5][6][7]. When the RWMs are destabilized, the RWM results in major collapse.…”

Section: Introductionmentioning

confidence: 99%

Nonlinear three-dimensional simulations of resistive wall modes

Sato

Nakajima

2006

J. Plasma Phys.

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Abstract. Nonlinear behavior of the resistive wall modes (RWMs) has been studied using nonlinear three-dimensional simulation code based on the reduced magnetohydrodynamic equations in a cylindrical tokamak. The vacuum is replaced by a highly resistive plasma using the pseudo-vacuum model. For the case that the RWM with (m, n) = (3, 1) mode and the internal (m, n) = (5, 2) mode are unstable, the RWM with (m, n) = (3, 1) mode enhances the growth rate of the internal (m, n) = (5, 2) mode in the nonlinear phase. The magnetic field line stochastization is obtained around the plasma edge due to the overlapping of the magnetic islands of the (m, n) = (3, 1) mode and the (m, n) = (5, 2) mode.

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Effect of toroidal plasma flow and flow shear on global magnetohydrodynamic MHD modes

Cited by 213 publications

References 12 publications

Numerical calculations demonstrating complete stabilization of the ideal magnetohydrodynamic resistive wall mode by longitudinal flow

Numerical calculations demonstrating complete stabilization of the ideal magnetohydrodynamic resistive wall mode by longitudinal flow

Physics of advanced tokamaks

Nonlinear three-dimensional simulations of resistive wall modes

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