Alfven cascade modes at high {beta} in the National Spherical Torus Experiment

Journal Article · Wed Oct 15 00:00:00 EDT 2008 · Physics of Plasmas

DOI:https://doi.org/10.1063/1.2993182· OSTI ID:21254537

Crocker, N A; Kubota, S ^[1]; Fredrickson, E D; Gorelenkov, N N; Kramer, G J; Darrow, D S; Menard, J E; LeBlanc, B P; Bell, R E ^[2]; Heidbrink, W W ^[3]; Levinton, F M; Yuh, H ^[4]

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1. University of California, Los Angeles, California 90095 (United States)
2. Princeton Plasma Physics Laboratory, Princeton, New Jersey 08543 (United States)
3. University of California, Irvine, California 92697 (United States)
4. Nova Photonics, Princeton, New Jersey 08543 (United States)

Alfven cascade (AC) modes are observed in the National Spherical Torus Experiment [M. Ono et al., Nucl. Fusion 40, 557 (2000)] reversed shear plasmas over a wide range (up to {approx}25% on axis, or {approx}11% at minimum q) of {beta} (ratio of kinetic pressure to magnetic pressure). At low {beta}, the AC mode spectrum shows characteristics similar to conventional tokamaks. At higher {beta}, distinct {beta} and {nabla}{beta} effects are observed in the spectrum, including a significant reduction in the relative size of the frequency sweep and a toroidal mode number dependence in the minimum mode frequency. AC mode structure is obtained using reflectometry. Fast-ion loss associated with AC mode activity is observed. AC mode polarization at the plasma edge is consistent with expectation. Magnetohydrodynamic (MHD) spectroscopy is shown to be usable to determine q{sub min} at both low {beta} and high {beta}. Observed AC mode structure and frequency are found to be consistent with calculations for the same plasma conditions and geometry using the linear, ideal MHD hybrid kinetic code NOVA-K[C. Z. Cheng, Phys. Rep. 211, 1 (1992)].

• OSTI ID: 21254537
• Journal Information: Physics of Plasmas, Vol. 15, Issue 10; Other Information: DOI: 10.1063/1.2993182; (c) 2008 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
ALFVEN WAVES
HIGH-BETA PLASMA
MAGNETOHYDRODYNAMICS
PLASMA CONFINEMENT
PLASMA DIAGNOSTICS
REVERSED SHEAR
SPECTROSCOPY
SPHERICAL CONFIGURATION
TOKAMAK DEVICES