The effect of off-axis neutral beam injection on sawtooth stability in ASDEX Upgrade and Mega-Ampere Spherical Tokamak

Journal Article · Wed Jul 15 00:00:00 EDT 2009 · Physics of Plasmas

DOI:https://doi.org/10.1063/1.3187905· OSTI ID:21277311

Chapman, I T; de Bock, M F; Pinches, S D; Turnyanskiy, M R ^[1]; Igochine, V G; Maraschek, M; Tardini, G ^[2]

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1. EURATOM/UKAEA Fusion Association, Culham Science Centre, Abingdon, Oxfordshire OX14 3DB (United Kingdom)
2. Max-Planck Institut fuer Plasmaphysik, Euratom-Association, D-85748 Garching (Germany)

Sawtooth behavior has been investigated in plasmas heated with off-axis neutral beam injection in ASDEX Upgrade [A. Herrmann and O. Gruber, Fusion Sci. Technol. 44, 569 (2003)] and the Mega-Ampere Spherical Tokamak (MAST) [A. Sykes et al., Nucl. Fusion 41, 1423 (2001)]. Provided that the fast ions are well confined, the sawtooth period is found to decrease as the neutral beam is injected further off-axis. Drift kinetic modeling of such discharges qualitatively shows that the passing fast ions born outside the q=1 rational surface can destabilize the n=1 internal kink mode, thought to be related to the sawtooth instability. This effect can be enhanced by optimizing the deposition of the off-axis beam energetic particle population with respect to the mode location.

• OSTI ID: 21277311
• Journal Information: Physics of Plasmas, Vol. 16, Issue 7; Other Information: DOI: 10.1063/1.3187905; (c) 2009 American Institute of Physics; Country of input: International Atomic Energy Agency (IAEA); ISSN 1070-664X
• Country of Publication: United States
• Language: English

Related Subjects

70 PLASMA PHYSICS AND FUSION TECHNOLOGY
ASDEX TOKAMAK
BEAM INJECTION HEATING
ELECTRIC DISCHARGES
KINK INSTABILITY
MAST TOKAMAK
SAWTOOTH OSCILLATIONS