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Title: A model for ideal {ital m}=1 internal kink stabilization by minority ion cyclotron resonant heating

Abstract

A generalized energy principle is used to determine the effect of ion cyclotron resonant heating (ICRH) on the stability of {ital m}=1 internal kink displacements in the low-frequency limit: such displacements are associated with sawtooth oscillations. An integral expression is obtained for the contribution to the plasma energy of an ICRH-heated minority ion population with strong temperature anisotropy, which relates the former to the ICRH power input and its deposition profile. The link is provided by a realistic, but analytically tractable, new model for the distribution function of the heated ions, which is based on the approach of Stix [Nucl. Fusion {bold 15}, 737 (1975)]. Numerical evaluation of the integral expression is carried out using parameters inferred from ICRH experiments in the Joint European Torus (JET) [Campbell {ital et} {ital al}., Phys. Rev. Lett. {bold 60}, 2148 (1988)]. It is shown that the ideal {ital m}=1 internal kink is stable at values of the poloidal plasma beta {beta}{sub {ital p}} which typically lie in the range 0.4--1, depending on the radio-frequency power input and the radius {ital r}{sub 1} of the {ital q}=1 surface. Stability is thus possible at values of {beta}{sub {ital p}} lying significantly above the magnetohydrodynamic instabilitymore » threshold ({congruent}0.3). If the perpendicular temperature {ital T}{sub {perpendicular}} of the hot ions exceeds the parallel temperature by a factor of 10 or more, and {ital r}{sub 1} is greater than about one-third of the plasma minor radius, trapped ions have a greater stabilizing effect than passing ions. Stabilization is most easily achieved, however, if {ital r}{sub 1} is small. The hot-ion plasma energy depends strongly on the value of {ital T}{sub {perpendicular}}, but for fixed {ital T}{sub {perpendicular}} is insensitive to the degree of anisotropy.« less

Authors:
; ; ;  [1]
  1. UKAEA Government Division, Fusion, Culham Laboratory (Euratom/UKAEA Fusion Association), Abingdon, Oxfordshire, OX14 3DB (United Kingdom)
Publication Date:
OSTI Identifier:
165182
Resource Type:
Journal Article
Journal Name:
Physics of Plasmas
Additional Journal Information:
Journal Volume: 2; Journal Issue: 5; Other Information: PBD: May 1995
Country of Publication:
United States
Language:
English
Subject:
70 PLASMA PHYSICS AND FUSION; KINK INSTABILITY; ICR HEATING; JET TOKAMAK; MEDIUM-BETA PLASMA; STABILIZATION; MAGNETOHYDRODYNAMICS

Citation Formats

Dendy, R O, Hastie, R J, McClements, K G, and Martin, T J. A model for ideal {ital m}=1 internal kink stabilization by minority ion cyclotron resonant heating. United States: N. p., 1995. Web. doi:10.1063/1.871457.
Dendy, R O, Hastie, R J, McClements, K G, & Martin, T J. A model for ideal {ital m}=1 internal kink stabilization by minority ion cyclotron resonant heating. United States. https://doi.org/10.1063/1.871457
Dendy, R O, Hastie, R J, McClements, K G, and Martin, T J. Mon . "A model for ideal {ital m}=1 internal kink stabilization by minority ion cyclotron resonant heating". United States. https://doi.org/10.1063/1.871457.
@article{osti_165182,
title = {A model for ideal {ital m}=1 internal kink stabilization by minority ion cyclotron resonant heating},
author = {Dendy, R O and Hastie, R J and McClements, K G and Martin, T J},
abstractNote = {A generalized energy principle is used to determine the effect of ion cyclotron resonant heating (ICRH) on the stability of {ital m}=1 internal kink displacements in the low-frequency limit: such displacements are associated with sawtooth oscillations. An integral expression is obtained for the contribution to the plasma energy of an ICRH-heated minority ion population with strong temperature anisotropy, which relates the former to the ICRH power input and its deposition profile. The link is provided by a realistic, but analytically tractable, new model for the distribution function of the heated ions, which is based on the approach of Stix [Nucl. Fusion {bold 15}, 737 (1975)]. Numerical evaluation of the integral expression is carried out using parameters inferred from ICRH experiments in the Joint European Torus (JET) [Campbell {ital et} {ital al}., Phys. Rev. Lett. {bold 60}, 2148 (1988)]. It is shown that the ideal {ital m}=1 internal kink is stable at values of the poloidal plasma beta {beta}{sub {ital p}} which typically lie in the range 0.4--1, depending on the radio-frequency power input and the radius {ital r}{sub 1} of the {ital q}=1 surface. Stability is thus possible at values of {beta}{sub {ital p}} lying significantly above the magnetohydrodynamic instability threshold ({congruent}0.3). If the perpendicular temperature {ital T}{sub {perpendicular}} of the hot ions exceeds the parallel temperature by a factor of 10 or more, and {ital r}{sub 1} is greater than about one-third of the plasma minor radius, trapped ions have a greater stabilizing effect than passing ions. Stabilization is most easily achieved, however, if {ital r}{sub 1} is small. The hot-ion plasma energy depends strongly on the value of {ital T}{sub {perpendicular}}, but for fixed {ital T}{sub {perpendicular}} is insensitive to the degree of anisotropy.},
doi = {10.1063/1.871457},
url = {https://www.osti.gov/biblio/165182}, journal = {Physics of Plasmas},
number = 5,
volume = 2,
place = {United States},
year = {1995},
month = {5}
}