DocumentCode :
1553294
Title :
Sawtooth Precursor Oscillations on DIII-D
Author :
Tobias, B.J. ; Domier, C.W. ; Luhmann, N.C. ; Boom, J.E. ; Classen, I.G.J. ; Donné, A. J H ; Yun, G. ; Park, H.K. ; Nazikian, R.M.
Author_Institution :
Dept. of Electr. & Comput. Eng., Univ. of California-Davis, Davis, CA, USA
Volume :
39
Issue :
11
fYear :
2011
Firstpage :
3022
Lastpage :
3023
Abstract :
The sawtooth oscillation, observed in tokamak plasmas with a central safety factor of less than unity, is a periodic disruptive instability characterized by a slow ramping of central plasma density and temperature, followed by a fast relaxation resulting in flattening of both profiles. Elongated neutral-beam-heated discharges on the DIII-D tokamak exhibit multiple precursor oscillations with mode number m/n = 1/1. The dominant m/n = 1/1 mode oscillates at the plasma rotation frequency. A downshifted mode also appears early in the sawtooth ramp. A normalization of electron cyclotron emission imaging data that removes the contribution of slow electron temperature profile evolution reveals that both modes are consistent with an underlying quasi-interchange plasma displacement.
Keywords :
Tokamak devices; plasma density; plasma diagnostics; plasma flow; plasma oscillations; plasma temperature; plasma toroidal confinement; plasma transport processes; radiometry; sawtooth instability; DIII-D tokamak; central plasma density; central plasma temperature; central safety factor; downshifted mode; electron cyclotron emission imaging data normalization; elongated neutral-beam-heated discharges; fast relaxation; mode number; multiple precursor oscillations; periodic disruptive instability; plasma rotation frequency; quasi-interchange plasma displacement; sawtooth precursor oscillations; sawtooth ramp; slow electron temperature profile evolution; tokamak plasmas; Approximation methods; Computer crashes; Imaging; Oscillators; Plasma temperature; Tokamaks; Millimeter-wave radiometry; plasma confinement; plasma temperature; plasma transport processes;
fLanguage :
English
Journal_Title :
Plasma Science, IEEE Transactions on
Publisher :
ieee
ISSN :
0093-3813
Type :
jour
DOI :
10.1109/TPS.2011.2157535
Filename :
5875900
Link To Document :
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