NBI fast ion confinement in the helical core of MAST hybrid-like plasmas

D. Pfefferlé, J. P. Graves, W. A. Cooper, C. Misev, I. T. Chapman, M. Turnyanskiy, S. Sangaroon

Research output: Contribution to journalArticle

20 Citations (Scopus)

Abstract

Energetic ions are found to be transported strongly from the core of MAST hybrid-like plasmas during long-lived mode (LLM) magnetohydrodynamic activity. The resulting impact on the neutral beam ion deposition and concurrent current drive is modelled using the guiding-centre approximation in the internal kinked magnetic topology. General coordinate guiding-centre equations are extended for this purpose. It is found that the kinked core spirals around the position of strongest ionization, which remains geometrically centred, so that a large fraction of the population is deposited in the high shear external region where the plasma is almost axisymmetric. Those particles ionized in the low shear region exhibit exotic drift motion due to the strongly non-axisymmetric equilibrium, periodically passing near the magnetic axis and then reflected by the boundary of the kinked equilibrium, which in this respect acts as a confining pinch. Broad agreement is found against experimental measurement of fast ion particle confinement degradation as the MAST LLM amplitude varies.

Original languageEnglish
Article number064020
JournalNuclear Fusion
Volume54
Issue number6
DOIs
Publication statusPublished - 1 Jan 2014
Externally publishedYes

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shear
ions
neutral beams
confining
magnetohydrodynamics
topology
degradation
ionization
approximation

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Pfefferlé, D., Graves, J. P., Cooper, W. A., Misev, C., Chapman, I. T., Turnyanskiy, M., & Sangaroon, S. (2014). NBI fast ion confinement in the helical core of MAST hybrid-like plasmas. Nuclear Fusion, 54(6), [064020]. https://doi.org/10.1088/0029-5515/54/6/064020
Pfefferlé, D. ; Graves, J. P. ; Cooper, W. A. ; Misev, C. ; Chapman, I. T. ; Turnyanskiy, M. ; Sangaroon, S. / NBI fast ion confinement in the helical core of MAST hybrid-like plasmas. In: Nuclear Fusion. 2014 ; Vol. 54, No. 6.
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Pfefferlé, D, Graves, JP, Cooper, WA, Misev, C, Chapman, IT, Turnyanskiy, M & Sangaroon, S 2014, 'NBI fast ion confinement in the helical core of MAST hybrid-like plasmas' Nuclear Fusion, vol. 54, no. 6, 064020. https://doi.org/10.1088/0029-5515/54/6/064020

NBI fast ion confinement in the helical core of MAST hybrid-like plasmas. / Pfefferlé, D.; Graves, J. P.; Cooper, W. A.; Misev, C.; Chapman, I. T.; Turnyanskiy, M.; Sangaroon, S.

In: Nuclear Fusion, Vol. 54, No. 6, 064020, 01.01.2014.

Research output: Contribution to journalArticle

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T1 - NBI fast ion confinement in the helical core of MAST hybrid-like plasmas

AU - Pfefferlé, D.

AU - Graves, J. P.

AU - Cooper, W. A.

AU - Misev, C.

AU - Chapman, I. T.

AU - Turnyanskiy, M.

AU - Sangaroon, S.

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N2 - Energetic ions are found to be transported strongly from the core of MAST hybrid-like plasmas during long-lived mode (LLM) magnetohydrodynamic activity. The resulting impact on the neutral beam ion deposition and concurrent current drive is modelled using the guiding-centre approximation in the internal kinked magnetic topology. General coordinate guiding-centre equations are extended for this purpose. It is found that the kinked core spirals around the position of strongest ionization, which remains geometrically centred, so that a large fraction of the population is deposited in the high shear external region where the plasma is almost axisymmetric. Those particles ionized in the low shear region exhibit exotic drift motion due to the strongly non-axisymmetric equilibrium, periodically passing near the magnetic axis and then reflected by the boundary of the kinked equilibrium, which in this respect acts as a confining pinch. Broad agreement is found against experimental measurement of fast ion particle confinement degradation as the MAST LLM amplitude varies.

AB - Energetic ions are found to be transported strongly from the core of MAST hybrid-like plasmas during long-lived mode (LLM) magnetohydrodynamic activity. The resulting impact on the neutral beam ion deposition and concurrent current drive is modelled using the guiding-centre approximation in the internal kinked magnetic topology. General coordinate guiding-centre equations are extended for this purpose. It is found that the kinked core spirals around the position of strongest ionization, which remains geometrically centred, so that a large fraction of the population is deposited in the high shear external region where the plasma is almost axisymmetric. Those particles ionized in the low shear region exhibit exotic drift motion due to the strongly non-axisymmetric equilibrium, periodically passing near the magnetic axis and then reflected by the boundary of the kinked equilibrium, which in this respect acts as a confining pinch. Broad agreement is found against experimental measurement of fast ion particle confinement degradation as the MAST LLM amplitude varies.

KW - current drive

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Pfefferlé D, Graves JP, Cooper WA, Misev C, Chapman IT, Turnyanskiy M et al. NBI fast ion confinement in the helical core of MAST hybrid-like plasmas. Nuclear Fusion. 2014 Jan 1;54(6). 064020. https://doi.org/10.1088/0029-5515/54/6/064020