Nonresonant suppression of the sawtooth instability by passing ions in tokamaks

Authors
Citation
A. Lazaros, Nonresonant suppression of the sawtooth instability by passing ions in tokamaks, PHYS PLASMA, 8(8), 2001, pp. 3695-3701
Citations number
9
Language
INGLESE
art.tipo
Article
Categorie Soggetti
Physics
Journal title
PHYSICS OF PLASMAS
ISSN journal
1070-664X → ACNP
Volume
8
Issue
8
Year of publication
2001
Pages
3695 - 3701
Database
ISI
SICI code
1070-664X(200108)8:8<3695:NSOTSI>2.0.ZU;2-4
Abstract
A new interpretation is presented for the well-known observation of sawteet h stabilization, during ion cyclotron resonant heating, in the Joint Europe an Tokamak [Campbell , Phys. Rev. Lett. 60, 2148 (1988)] and the Tokamak Fu sion Test Reactor [Phillips , Phys. Fluids B 4, 2155 (1992)]. It is shown t hat the radial fluxes of superthermal and thermal ions exchange a finite am ount of power with the m=1 mode (associated with the sawtooth instability) which is suppressed. The dominant contribution to this effect is provided b y the passing ions, which experience in the presence of the mode a much fas ter (than the trapped ions) radial diffusion. This is a nonresonant electro static interaction between the passing ions and the finite parallel electri c field (along the perturbed magnetic field line), which takes place at any mode frequency. For the requirements of the present theory, the concepts o f the finite parallel electric field, and the diffusion of passing ions, in the presence of a magnetic mode are also developed. The present work also provides the interpretation for the suppression of the sawtooth instability by passing ions, during tangential neutral beam injection, in the Japan At omic Energy Research Institute Tokamak Upgrade (JT-60U) [Kramer , Nucl. Fus ion 40, 1383 (2000)]. (C) 2001 American Institute of Physics.