The ambipolar electric field and neoclassical heat and particle flows in nonaxisymmetric toroidal multispecies plasmas with sources

Coronado, M.; Wobig, H.

doi:10.1063/1.866492

Cited by 18 publications

(9 citation statements)

References 17 publications

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“…This is one of the merits often cited when comparing stellarators and tokamaks as thermonuclear fusion reactors. However, bootstrap current exists in stellarators as well due to finite plasma gradients [53,54]. It has to be taken into account in MHD equilibrium calculations [55].…”

Section: Equilibrium Parallel Current Densitymentioning

confidence: 99%

Neoclassical plasma viscosity and transport processes in non-axisymmetric tori

2015

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Neoclassical transport processes are important to the understanding of plasma confinement physics in doubly periodic magnetized toroidal plasmas, especially, after the impact of the momentum confinement on the particle and energy confinement is recognized. Real doubly periodic tori in general are non-axisymmetric, with symmetric tori as a special case. An eight-moment approach to transport theory with plasma density N, plasma pressure p, mass flow velocity V and heat flow q as independent variables is adopted. Transport processes are dictated by the solutions of the momentum and heat flux balance equations. For toroidal plasma confinement devices, the first order (in the gyro-radius ordering) plasma flows are on the magnetic surface to guarantee good plasma confinement and are thus two-dimensional. Two linearly independent components of the momentum equation are required to determine the flows completely. Once this two-dimensional flow is relaxed, i.e. the momentum equation reaches a steady state, plasmas become ambipolar, and all the transport fluxes are determined through the flux-force relation. The flux-force relation is derived both from the kinetic definitions for the transport fluxes and from the manipulation of the momentum and heat flux balance equations to illustrate the nature of the transport fluxes by examining their corresponding driven forces and their roles in the momentum and heat flux balance equations. Steady-state plasma flows are determined by the components of the stress and heat stress tensors in the momentum and heat flux balance equations. This approach emphasizes the pivotal role of the momentum equation in the transport processes and is particularly useful in modelling plasma flows in experiments. The methodology for neoclassical transport theory is applied to fluctuation-driven transport fluxes in the quasilinear theory to unify these two theories. Experimental observations in tokamaks and stellarators for the physics discussed are presented.

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Section: Equilibrium Parallel Current Densitymentioning

confidence: 99%

Neoclassical plasma viscosity and transport processes in non-axisymmetric tori

2015

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“…Note that inclusion of temperature gradient effects in the viscosities would modify this expression, 8,35,42 allowing for flow with no external radial current. It is not anticipated that these corrections are important for the low density ECH plasmas described in this article, where cool ions and small ion temperature gradients are inferred from Doppler spectroscopy.…”

Section: A the Steady State Radial Conductivity And Flow Directionmentioning

confidence: 99%

Measurements and modeling of plasma flow damping in the Helically Symmetric eXperiment

et al. 2005

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Fusion Technology 27, 273 ͑1995͔͒ using a biased electrode to impulsively spin the plasma and Mach probes to measure the rotation. There is a distinct asymmetry between the spin-up when the bias is initiated and relaxation when the electrode current is broken. In each case, two time-scales are observed in the evolution of the plasma flow. These observations motivate the development of new neoclassical modeling techniques, including a new model where the fast increment of the electric field initiates the spin-up process. The flow in the quasisymmetric configuration rises more slowly and to a higher value than in a configuration with the quasisymmetry broken, and the rise time-scale is in reasonable agreement with the neoclassical spin-up model. The flows decay more slowly in the quasisymmetry configuration than in the configuration with the quasisymmetry broken, although the decay rates are significantly faster than the neoclassical prediction.

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“…Stellartor impurity transport has been considered in the literature before, mainly in the framework of the Hirshman-Sigmar moment formalism [2,3]. The present calculation, which is based on the direct expansion of the drift kinetic equation by Hazeltine and Hinton [4], retains some terms of geometrical nature that are otherwise neglected, see, e.g.…”

Section: Introductionmentioning

confidence: 99%

Pfirsch–Schlüter impurity transport in stellarators

Braun

Helander

2010

Physics of Plasmas

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The Pfirsch-Schlüter transport of impurities is calculated for stellarator geometry. Contrary to the tokamak case, where the only contribution to the particle flux arises from friction between different species, in a stellarator there is another source of impurity transport due to pressure anisotropy. However, the pressure anisotropy term is usually smaller than the friction term, so that the impurity particle flux is comparable to that in a tokamak. The pressure anisotropy is nonetheless important as it causes the transport to be non-ambipolar and thereby determines the radial electric field. The presence of impurities therefore affects the radial electric field in a stellarator. The heat flux is also affected qualitatively by impurities.

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The ambipolar electric field and neoclassical heat and particle flows in nonaxisymmetric toroidal multispecies plasmas with sources

Cited by 18 publications

References 17 publications

Neoclassical plasma viscosity and transport processes in non-axisymmetric tori

Neoclassical plasma viscosity and transport processes in non-axisymmetric tori

Measurements and modeling of plasma flow damping in the Helically Symmetric eXperiment

Pfirsch–Schlüter impurity transport in stellarators

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