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Title: Collisional diffusion in toroidal plasmas with elongation and triangularity

Abstract

Collisional diffusion is analyzed for plasma tokamaks with different ellipticities and triangularities. Improved nonlinear equations for the families of magnetic surfaces are used here. Dimensionless average velocities are calculated as a function of the inductive electric field, elongation, triangularity, and Shafranov shift. Confinement has been found to depend significantly on triangularity.

Authors:
; ;  [1];  [2]
  1. Departamento de Fisica, Universidad Simon Bolivar, Apartado. 89000, Caracas 1080A (Venezuela)
  2. (United Kingdom)
Publication Date:
OSTI Identifier:
20974983
Resource Type:
Journal Article
Resource Relation:
Journal Name: Physics of Plasmas; Journal Volume: 14; Journal Issue: 5; Other Information: DOI: 10.1063/1.2727455; (c) 2007 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; COLLISIONS; DIFFUSION; ELECTRIC FIELDS; ELONGATION; EQUATIONS; MAGNETIC SURFACES; NONLINEAR PROBLEMS; PLASMA; PLASMA CONFINEMENT; TOKAMAK DEVICES

Citation Formats

Martin, P., Castro, E., Haines, M. G., and Blackett Laboratory, Imperial College, London SW7 2BZ, England. Collisional diffusion in toroidal plasmas with elongation and triangularity. United States: N. p., 2007. Web. doi:10.1063/1.2727455.
Martin, P., Castro, E., Haines, M. G., & Blackett Laboratory, Imperial College, London SW7 2BZ, England. Collisional diffusion in toroidal plasmas with elongation and triangularity. United States. doi:10.1063/1.2727455.
Martin, P., Castro, E., Haines, M. G., and Blackett Laboratory, Imperial College, London SW7 2BZ, England. Tue . "Collisional diffusion in toroidal plasmas with elongation and triangularity". United States. doi:10.1063/1.2727455.
@article{osti_20974983,
title = {Collisional diffusion in toroidal plasmas with elongation and triangularity},
author = {Martin, P. and Castro, E. and Haines, M. G. and Blackett Laboratory, Imperial College, London SW7 2BZ, England},
abstractNote = {Collisional diffusion is analyzed for plasma tokamaks with different ellipticities and triangularities. Improved nonlinear equations for the families of magnetic surfaces are used here. Dimensionless average velocities are calculated as a function of the inductive electric field, elongation, triangularity, and Shafranov shift. Confinement has been found to depend significantly on triangularity.},
doi = {10.1063/1.2727455},
journal = {Physics of Plasmas},
number = 5,
volume = 14,
place = {United States},
year = {Tue May 15 00:00:00 EDT 2007},
month = {Tue May 15 00:00:00 EDT 2007}
}
  • Non-linear plasma diffusion effects due to hole currents in tokamaks is analyzed in this work. Since the recent discovery of hole currents in tokamaks, this matter has become very important in confinement and instabilities in tokamaks plasmas. The analysis here presented includes non-linear flows as well as hole currents. In the case of low vorticity plasmas our treatment is performed using MHD equations, an it is more suitable for plasmas with very low levels of turbulence, as in the H-mode. The present treatment follows the lines of previous works, and some of the equations and results look like those obtainedmore » on these papers. However, the form of the family of the magnetic surfaces is very different to previous treatment, since the hole current modifies those families in a very important way. Elliptic plasmas with triangularity are considered. Pfirsch-Schlueter type currents are obtained for these generalized cases. Diffusion with and without holes are calculated and compared for several values of ellipticity and triangularity. Negative and positive triangularities are considered. In most of the calculations triangularity improves confinement, but the results are different for the positive than for the negative case.« less
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  • Quasianalytic formulas are calculated for the elongation {kappa} and triangularity {delta} of the plasma surface of a free-boundary tokamak equilibrium. The final results give {kappa} and {delta} as functions of five quantities: the inverse aspect ratio {epsilon}, the poloidal beta {beta}{sub {ital p}}, the internal inductance {ital l}{sub {ital i}}, and the quadrupole and hexapole moments of the externally applied field. The agreement with numerically computed equilibria is found to be quite good when {ital A}{ge}3, {kappa}{le}1.5, and {delta}{le}0.2 and when the plasma is limited by the vacuum vessel wall and not diverted by the presence of a separatrix onmore » the plasma surface.« less
  • Lower-hybrid (LH) wave propagation is studied for a general magnetic-field configuration. The ray-tracing equations in the geometric optics approximation are analytically and numerically solved in flux surface coordinates by using asymptotic techniques. In particular, the effects of elongation, triangularity, and the Shafranov shift on wave penetration are pointed out. Numerical applications devoted to the study of current drive generation for the International Thermonuclear Experimental Reactor (ITER) [Nucl. Fusion [bold 31], 1135 (1991)] plasma parameters will also be presented.
  • An expression for the pressure anisotropy and thus for the viscous stress in the plateau regime is derived for arbitrary toroidal magnetic configurations without assuming incompressibility or the existence of flux surfaces, without neglecting the flow components perpendicular to the magnetic surface, and without restricting the flow velocity to be a constant on the flux surface. It can be employed to study low-frequency instabilities in the long mean-free-path regime. A smoothly connected formula for the pressure anisotropy, valid in both the collisional fluid regime and the plateau regime, is given to facilitate the numerical computation. An alternative interpretation of themore » neoclassical transport theory is also obtained. It is found that if the effects of the temperature gradient are neglected, neoclassical transport fluxes can be interpreted as driven by the velocity stress.« less