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Title: A new, explicitly collisional contribution to the gyroviscosity and the radial electric field in a collisional tokamak

Abstract

An additional contribution to the ion viscosity for a collisional plasma is evaluated and found to be the same order as other temperature gradient terms in the collisional perpendicular viscosity. The new contribution arises because of an explicitly collisional portion of the ion distribution function. The evaluation of the Pfirsch-Schlueter radial electric field in a collisional tokamak of arbitrary cross section is extended to retain the new contribution. In a spherical tokamak this new contribution must be retained in determining the radial electric field, while in a conventional tokamak it is small by 1/q{sup 2}, where q is the safety factor.

Authors:
;  [1];  [2]
  1. MIT Plasma Science and Fusion Center, Cambridge, Massachusetts 02139 (United States)
  2. (United States)
Publication Date:
OSTI Identifier:
20782369
Resource Type:
Journal Article
Resource Relation:
Journal Name: Physics of Plasmas; Journal Volume: 12; Journal Issue: 11; Other Information: DOI: 10.1063/1.2136355; (c) 2005 American Institute of Physics; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
70 PLASMA PHYSICS AND FUSION TECHNOLOGY; CHARGED-PARTICLE TRANSPORT; COLLISIONAL PLASMA; DISTRIBUTION FUNCTIONS; ELECTRIC FIELDS; ELECTRON COLLISIONS; ELECTRON TEMPERATURE; ION COLLISIONS; ION TEMPERATURE; IONS; PLASMA CONFINEMENT; SPHERICAL CONFIGURATION; TEMPERATURE GRADIENTS; TOKAMAK DEVICES; VISCOSITY

Citation Formats

Catto, P.J., Simakov, A.N., and Los Alamos National Laboratory, Los Alamos, New Mexico 87545. A new, explicitly collisional contribution to the gyroviscosity and the radial electric field in a collisional tokamak. United States: N. p., 2005. Web. doi:10.1063/1.2136355.
Catto, P.J., Simakov, A.N., & Los Alamos National Laboratory, Los Alamos, New Mexico 87545. A new, explicitly collisional contribution to the gyroviscosity and the radial electric field in a collisional tokamak. United States. doi:10.1063/1.2136355.
Catto, P.J., Simakov, A.N., and Los Alamos National Laboratory, Los Alamos, New Mexico 87545. Tue . "A new, explicitly collisional contribution to the gyroviscosity and the radial electric field in a collisional tokamak". United States. doi:10.1063/1.2136355.
@article{osti_20782369,
title = {A new, explicitly collisional contribution to the gyroviscosity and the radial electric field in a collisional tokamak},
author = {Catto, P.J. and Simakov, A.N. and Los Alamos National Laboratory, Los Alamos, New Mexico 87545},
abstractNote = {An additional contribution to the ion viscosity for a collisional plasma is evaluated and found to be the same order as other temperature gradient terms in the collisional perpendicular viscosity. The new contribution arises because of an explicitly collisional portion of the ion distribution function. The evaluation of the Pfirsch-Schlueter radial electric field in a collisional tokamak of arbitrary cross section is extended to retain the new contribution. In a spherical tokamak this new contribution must be retained in determining the radial electric field, while in a conventional tokamak it is small by 1/q{sup 2}, where q is the safety factor.},
doi = {10.1063/1.2136355},
journal = {Physics of Plasmas},
number = 11,
volume = 12,
place = {United States},
year = {Tue Nov 15 00:00:00 EST 2005},
month = {Tue Nov 15 00:00:00 EST 2005}
}
  • No abstract prepared.
  • The neoclassical electric field in a tokamak is determined by the conservation of toroidal angular momentum. In the steady state in the absence of momentum sources and sinks it is explicitly evaluated by the condition that radial flux of toroidal angular momentum vanishes. For a collisional or Pfirsch-Schlueter short mean-free path ordering with subsonic plasma flows we find that there are two limiting cases of interest. The first is the simpler case of a strongly up-down asymmetric tokamak for which the lowest order gyroviscosity does not vanish and must be balanced by the leading order collisional viscosity in order tomore » determine the radial electric field. The second case is the more complicated case of an up-down symmetric tokamak for which the gyroviscosity must be evaluated to higher order and again balanced by the lowest order collisional viscosity to determine the radial electric field. In general, both the lowest and the next order contributions from the gyroviscosity must be retained.« less
  • Collisional plasma confined by magnetic fields in a screw-pinch and any axisymmetric, up-down symmetric closed magnetic field line configuration (such as a dipole or a field reversed configuration) is considered, and equations governing the evolution of the self-consistent radial electric field and flow are derived for each case, provided that effects of plasma fluctuations are negligible.
  • The low-frequency instability of a cylindrical poorly magnetized plasma with an inward-directed radial electric field is studied changing the gas pressure and the ion cyclotron frequency. The unstable frequency always decreases when the gas pressure is increased indicating collisional effects. At a fixed pressure, the unstable frequency increases with the magnetic field when the B-field is low and decreases at larger magnetic field strength. We find that the transition between these two regimes is obtained when the ion cyclotron frequency equals the ion-neutrals collision frequency. This is in agreement with the theory of the slow-ion drift instability induced by themore » collisional slowing of the electric ion drift [A. Simon, Phys. Fluids 6, 382 (1963)].« less
  • The Electric Tokamak (ET), currently under construction at the University of California{endash}Los Angeles, is designed to rotate poloidally via a radial current induced by fast wave rf heating fast enough to bifurcate the plasma into a global {open_quotes}{ital H} mode{close_quotes} ({open_quotes}high confinement mode{close_quotes}). A global gyrokinetic code is used to explore and illustrate some of the effects on ion temperature gradient turbulence. The realistic radial electric field required to completely suppress these modes for ET parameters is demonstrated to be {lt}{minus}30 V/cm at its maximum near the half radius. The effects of {ital both} a poloidally supersonic bulk rotation thresholdmore » and the shear in this rotation near that supersonic threshold were shown to be important in reducing these modes. {copyright} {ital 1999 American Institute of Physics.}« less