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Title: Roles of effective helical ripple rates in nonlinear stability of externally induced magnetic islands

Magnetic islands are externally produced by resonant magnetic perturbations (RMPs) in toroidal plasmas. Spontaneous annihilation of RMP-induced magnetic islands called self-healing has been observed in helical systems. A possible mechanism of the self-healing is shielding of RMP penetration by helical ripple-induced neoclassical flows, which give rise to neoclassical viscous torques. In this study, effective helical ripple rates in multi-helicity helical systems are revisited, and a multi-helicity effect on the self-healing is investigated, based on a theoretical model of rotating magnetic islands. It is confirmed that effective helical ripple rates are sensitive to magnetic axis positions. It is newly found that self-healing thresholds also strongly depend on magnetic axis positions, which is due to dependence of neoclassical viscous torques on effective helical ripple rates.
Authors:
 [1]
  1. Kobe City College of Technology, Kobe, Hyogo 651-2194 (Japan)
Publication Date:
OSTI Identifier:
22408116
Resource Type:
Journal Article
Resource Relation:
Journal Name: Physics of Plasmas; Journal Volume: 22; Journal Issue: 2; Other Information: (c) 2015 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; ANNIHILATION; DISTURBANCES; HEATING; HELICITY; MAGNETIC ISLANDS; NEOCLASSICAL TRANSPORT THEORY; NONLINEAR PROBLEMS; PLASMA; SHIELDING; STABILITY; TOROIDAL CONFIGURATION; TORQUE