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Modelling of minority ion cyclotron current drive during the activated phase of ITER
KTH, School of Electrical Engineering (EES), Centres, Alfvén Laboratory Centre for Space and Fusion Plasma Physics.
KTH, School of Electrical Engineering (EES), Centres, Alfvén Laboratory Centre for Space and Fusion Plasma Physics.
2005 (English)In: Nuclear Fusion, ISSN 0029-5515, E-ISSN 1741-4326, Vol. 45, no 12, 1510-1523 p.Article in journal (Refereed) Published
Abstract [en]

Neoclassical tearing modes, triggered by the long-period sawteeth expected in tokamaks with large non-thermal α-particle populations, may impose a severe β limit on experiments with large fusion yields and on reactors. Sawtooth destabilization by localized current drive could relax the β limit and improve plasma performance. 3He minority ion cyclotron current drive around the sawtooth inversion radius has been planned for ITER. Several ion species, including beam injected D ions and fusion born α particles, are however also resonant in the plasma and may represent a parasitic absorption of RF power. Modelling of minority ion cyclotron current drive in an ITER-FEAT-like plasma is presented, including the effects of ion trapping, finite ion drift orbit widths, wave-induced radial transport and the coupled evolution of wave fields and resonant ion distributions. The parasitic absorption of RF power by the other resonant species is concluded to be relatively small, but the 3He minority current drive is nevertheless negligible due to the strong collisionality of the 3He ions and the drag current by toroidally counter-rotating background ions and co-rotating electrons. H minority current drive is found to be a significantly more effective alternative.

Place, publisher, year, edition, pages
2005. Vol. 45, no 12, 1510-1523 p.
Keyword [en]
Absorption, Electric currents, Electrons, Plasmas, Co-rotating electrons, Localized current drive, Minority ion cyclotron currents, Resonant ion drive, Tokamak devices
National Category
Engineering and Technology
Identifiers
URN: urn:nbn:se:kth:diva-12714DOI: 10.1088/0029-5515/45/12/006ISI: 000234452300009Scopus ID: 2-s2.0-28844470775OAI: oai:DiVA.org:kth-12714DiVA: diva2:318262
Note
QC 20100507Available from: 2010-05-07 Created: 2010-05-07 Last updated: 2017-12-12Bibliographically approved
In thesis
1. Fast wave heating and current drive in tokamaks
Open this publication in new window or tab >>Fast wave heating and current drive in tokamaks
2005 (English)Doctoral thesis, comprehensive summary (Other scientific)
Abstract [en]

This thesis concerns heating and current drive in tokamak plasmas using the fast magnetosonic wave in the ion cyclotron range of frequencies. Fast wave heating is a versatile heating method for thermonuclear fusion plasmas and can provide both ion and electron heating and non-inductive current drive. Predicting and interpreting realistic heating scenarios is however difficult due to the coupled evolution of the cyclotron resonant ion velocity distributions and the wave field. The SELFO code, which solves the coupled wave equation and Fokker-Planck equation for cyclotron resonant ion species in a self-consistent manner, has been upgraded to allow the study of more advanced fast wave heating and current drive scenarios in present day experiments and in preparation for the ITER tokamak.

Theoretical and experimental studies related to fast wave heating and current drive with emphasis on fast ion effects are presented. Analysis of minority ion cyclotron current drive in ITER indicates that the use of a hydrogen minority rather than the proposed helium-3 minority results in substantially more efficient current drive. The parasitic losses of power to fusion born alpha particles and beam injected ions are concluded to be acceptably low. Experiments performed at the JET tokamak on polychromatic ion cyclotron resonance heating and on fast wave electron current drive are presented and analysed. Polychromatic heating is demonstrated to increase the bulk plasma ion to electron heating ratio, in line with theoretical expectations, but the fast wave electron current drive is found to be severely degraded by parasitic power losses outside of the plasma. A theoretical analysis of parasitic power losses at radio frequency antennas indicates that the losses can be significantly increased in scenarios with low wave damping and with narrow antenna spectra, such as in electron current drive scenarios.

Place, publisher, year, edition, pages
Stockholm: KTH, 2005. xiv, 42 p.
Keyword
Tokamak, JET, ITER, thermonuclear fusion, fast wave, heating, current drive, ion cyclotron resonance, polychromatic, finite orbit widths, RF-induced transport, neutral beam injection, fusion born alpha particles, magnetosonic eigenmodes, parasitic absorption, modelling, weighted Monte Carlo scheme, Fysik
National Category
Physical Sciences
Identifiers
urn:nbn:se:kth:diva-118 (URN)91-7283-954-6 (ISBN)
Public defence
2005-02-08, Kollegiesalen, Valhallavägen 79, Stockholm, 10:00 (English)
Opponent
Supervisors
Note
QC 20100506Available from: 2005-02-04 Created: 2005-02-04 Last updated: 2011-02-24Bibliographically approved

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