Pedestal density fluctuation dynamics during the inter-ELM cycle in DIII-D
- University of Wisconsin-Madison, 1500 Engineering Dr., Madison, Wisconsin 53706 (United States)
- General Atomics, PO Box 85608, San Diego, California 92186-5608 (United States)
- EURATOM/CCFE Fusion Association, Culham Science Centre, Abingdon OX 14 3DB (United Kingdom)
Detailed 2D measurements of long-wavelength density fluctuations in the pedestal region with beam emission spectroscopy during the period between edge localized modes (ELMs) indicate two distinct bands of fluctuations propagating in opposite poloidal directions in the plasma frame: one lower frequency band (50-150 kHz) advects in the ion-diamagnetic drift direction (ion mode) and a higher frequency band (200-400 kHz) advects in the electron diamagnetic drift direction (electron mode). The ion mode amplitude is modulated with the ELM cycle: it increases rapidly after an ELM and then saturates, similar to the evolution of the pedestal electron pressure and density gradients. The electron mode, in contrast, has no significant time evolution between ELMs. The decorrelation time of the ion mode is <5 {mu}s[{tau}{sub c}(c{sub s}/c{sub s}aa){<=}1], the radial correlation length is of order 10 {rho}{sub i} and has poloidal wave-number k{sub {theta}{rho}i{approx}}0.1, and the mode advects at near the ion diamagnetic velocity in the plasma frame. These spatiotemporal dynamics are qualitatively similar to features predicted for kinetic ballooning modes.
- OSTI ID:
- 21537880
- Journal Information:
- Physics of Plasmas, Vol. 18, Issue 5; Other Information: DOI: 10.1063/1.3590936; (c) 2011 American Institute of Physics; ISSN 1070-664X
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
BALLOONING INSTABILITY
BEAM-PLASMA SYSTEMS
DOUBLET-3 DEVICE
EDGE LOCALIZED MODES
EMISSION SPECTROSCOPY
FLUCTUATIONS
PLASMA DENSITY
CLOSED PLASMA DEVICES
INSTABILITY
PLASMA INSTABILITY
PLASMA MACROINSTABILITIES
SPECTROSCOPY
THERMONUCLEAR DEVICES
TOKAMAK DEVICES
VARIATIONS