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Title: Axisymmetric curvature-driven instability in a model divertor geometry

A model problem is presented which qualitatively describes a pressure-driven instability which can occur near the null-point in the divertor region of a tokamak where the poloidal field becomes small. The model problem is described by a horizontal slot with a vertical magnetic field which plays the role of the poloidal field. Line-tying boundary conditions are applied at the planes defining the slot. A toroidal field lying parallel to the planes is assumed to be very strong, thereby constraining the possible structure of the perturbations. Axisymmetric perturbations which leave the toroidal field unperturbed are analyzed. Ideal magnetohydrodynamics is used, and the instability threshold is determined by the energy principle. Because of the boundary conditions, the Euler equation is, in general, non-separable except at marginal stability. This problem may be useful in understanding the source of heat transport into the private flux region in a snowflake divertor which possesses a large region of small poloidal field, and for code benchmarking as it yields simple analytic results in an interesting geometry.
Authors:
 [1] ;  [2] ;  [3]
  1. Physics and Astronomy Department, University of California Los Angeles, Los Angeles, California 90095 (United States)
  2. (United States)
  3. Lawrence Livermore National Laboratory, 7000 East Ave., Livermore, California 94550 (United States)
Publication Date:
OSTI Identifier:
22220584
Resource Type:
Journal Article
Resource Relation:
Journal Name: Physics of Plasmas; Journal Volume: 20; Journal Issue: 9; Other Information: (c) 2013 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
70 PLASMA PHYSICS AND FUSION TECHNOLOGY; AXIAL SYMMETRY; BENCHMARKS; BOUNDARY CONDITIONS; DIVERTORS; GEOMETRY; HEAT TRANSFER; MAGNETIC FIELDS; MAGNETOHYDRODYNAMICS; PERTURBATION THEORY; PLASMA; PLASMA CONFINEMENT; PLASMA INSTABILITY; THERMONUCLEAR REACTORS; TOKAMAK DEVICES