Absorption of Fast Waves at Moderate to High Ion Cyclotron Harmonics on DIII-D

The absorption of fast Alfven waves (FW) by ion cyclotron harmonic damping in the range of harmonics from fourth to eighth is studied theoretically and with experiments in the DIII-D tokamak. A formula for linear ion cyclotron absorption on Maxwellian ion species is used to estimate the single-pass...

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Bibliographic Details
Published in:AIP conference proceedings 2005-09, Vol.787 (1)
Main Authors: Pinsker, R.I., Petty, C.C., Prater, R., Choi, M., Porkolab, M., Heidbrink, W.W., Luo, Y., Baity, F.W., Murakami, M., Fredd, E., Hosea, J.C., Harvey, R.W., Smirnov, A.P., Van Zeeland, M.A.
Format: Article
Language:English
Subjects:
70 PLASMA PHYSICS AND FUSION TECHNOLOGY
ABSORPTION
ALFVEN WAVES
BEAM INJECTION HEATING
CYCLOTRON HARMONICS
DAMPING
DOUBLET-3 DEVICE
ELECTROMAGNETIC RADIATION
IONS
L-MODE PLASMA CONFINEMENT
MHZ RANGE
NEUTRAL ATOM BEAM INJECTION
PLASMA
PLASMA DENSITY
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Summary:The absorption of fast Alfven waves (FW) by ion cyclotron harmonic damping in the range of harmonics from fourth to eighth is studied theoretically and with experiments in the DIII-D tokamak. A formula for linear ion cyclotron absorption on Maxwellian ion species is used to estimate the single-pass damping for various cases of experimental interest. It is found that damping on fast ions from neutral beam injection can be significant even at the eighth harmonic if the fast ion beta and the background plasma density are both high enough. The predictions are tested in several L-mode experiments in DIII-D with FW power at 60 MHz and at 116 MHz. It is found that 4th and 5th harmonic absorption of the 60 MHz power on the beam ions can be quite strong, but 8th harmonic absorption of the 116 MHz power appears to be weaker than expected. Possible explanations of the discrepancy are discussed.
ISSN:0094-243X
1551-7616
DOI:10.1063/1.2098199