Open AccessMagnetohydodynamics stability of compact stellarators
Author(s) -
G. Y. Fu,
L.P. Ku,
W.A. Cooper,
Steven Hirshman
Publication year - 2000
Publication title -
osti oai (u.s. department of energy office of scientific and technical information)
Language(s) - English
Resource type - Reports
DOI - 10.2172/750055
Subject(s) - rotational symmetry , curvature , physics , aspect ratio (aeronautics) , flux (metallurgy) , limit (mathematics) , pressure gradient , current (fluid) , beta (programming language) , mechanics , shear (geology) , stability (learning theory) , bootstrap current , constant (computer programming) , tokamak , plasma , geometry , mathematical analysis , materials science , mathematics , quantum mechanics , thermodynamics , computer science , optoelectronics , machine learning , metallurgy , composite material , programming language
Recent stability results of external kink modes and vertical modes in compact stellarators are presented. The vertical mode is found to be stabilized by externally generated poloidal flux. A simple stability criterion is derived in the limit of large aspect ratio and constant current density. For a wall at infinite distance from the plasma, the amount of external flux needed for stabilization is given by Fi = (k2 {minus} k)=(k2 + 1), where k is the axisymmetric elongation and Fi is the fraction of the external rotational transform. A systematic parameter study shows that the external kink mode in QAS can be stabilized at high beta ({approximately} 5%) without a conducting wall by magnetic shear via 3D shaping. It is found that external kinks are driven by both parallel current and pressure gradient. The pressure contributes significantly to the overall drive through the curvature term and the Pfirsch-Schluter current
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