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Title: EFFECT OF ION B DRIFT DIRECTION ON TURBULENCE FLOW AND FLOW SHEAR

Abstract

The divertor magnetic geometry has a significant effect on the poloidal flow and resulting flow shear of turbulence in the outer region of L-mode tokamak plasmas, as determined via two-dimensional measurements of density fluctuations with Beam Emission Spectroscopy on DIII-D. Plasmas with similar parameters, except that in one case the ion {del}B drift points towards the divertor X-point (lower single-null, LSN), and in the other case, the ion {del}B drift points away from the divertor X-point (upper single-null, USN), are compared. Inside of r/a=0.9, the turbulence characteristics (amplitude, flow direction, correlation lengths) are similar in both cases, while near r/a=0.92, a dramatic reversal of the poloidal flow of turbulence relative to the core flow direction is observed in plasmas with the ion {del}B drift pointing towards the divertor X-point. No such flow reversal is observed in plasmas with the ion {del}B drift pointing away from the divertor X-point. This poloidal flow reversal results in a significantly larger local shear in the poloidal turbulence flow velocity in plasmas with the ion {del}B drift pointing towards the divertor X-point. Additionally, these plasmas locally exhibit significant dispersion, with two distinct and counter-propagating turbulence modes. Likewise, the radial correlation length of the turbulence ismore » reduced in these plasmas, consistent with biorthogonal decomposition measurements of dominant turbulence structures. The naturally occurring turbulence flow shear in these LSN plasmas may facilitate the LH transition that occurs at an input power of roughly one-half to one-third that of corresponding plasmas with the ion {del}B drift pointing away from the X-point.« less

Authors:
; ; ; ; ;
Publication Date:
Research Org.:
GENERAL ATOMICS
Sponsoring Org.:
USDOE
OSTI Identifier:
837212
Report Number(s):
GA-A24409
TRN: US0701844
DOE Contract Number:  
AC03-99ER54463
Resource Type:
Journal Article
Country of Publication:
United States
Language:
English
Subject:
70 PLASMA PHYSICS AND FUSION TECHNOLOGY; DIVERTORS; EMISSION SPECTROSCOPY; FLUCTUATIONS; GEOMETRY; SHEAR; TURBULENCE; VELOCITY

Citation Formats

FENZI,C, McKEE,G.R, BURRELL,K.H, CARLSTROM,T.N, FONCK,R.J, and GROEBNER,R.J. EFFECT OF ION B DRIFT DIRECTION ON TURBULENCE FLOW AND FLOW SHEAR. United States: N. p., 2003. Web.
FENZI,C, McKEE,G.R, BURRELL,K.H, CARLSTROM,T.N, FONCK,R.J, & GROEBNER,R.J. EFFECT OF ION B DRIFT DIRECTION ON TURBULENCE FLOW AND FLOW SHEAR. United States.
FENZI,C, McKEE,G.R, BURRELL,K.H, CARLSTROM,T.N, FONCK,R.J, and GROEBNER,R.J. Tue . "EFFECT OF ION B DRIFT DIRECTION ON TURBULENCE FLOW AND FLOW SHEAR". United States. https://www.osti.gov/servlets/purl/837212.
@article{osti_837212,
title = {EFFECT OF ION B DRIFT DIRECTION ON TURBULENCE FLOW AND FLOW SHEAR},
author = {FENZI,C and McKEE,G.R and BURRELL,K.H and CARLSTROM,T.N and FONCK,R.J and GROEBNER,R.J},
abstractNote = {The divertor magnetic geometry has a significant effect on the poloidal flow and resulting flow shear of turbulence in the outer region of L-mode tokamak plasmas, as determined via two-dimensional measurements of density fluctuations with Beam Emission Spectroscopy on DIII-D. Plasmas with similar parameters, except that in one case the ion {del}B drift points towards the divertor X-point (lower single-null, LSN), and in the other case, the ion {del}B drift points away from the divertor X-point (upper single-null, USN), are compared. Inside of r/a=0.9, the turbulence characteristics (amplitude, flow direction, correlation lengths) are similar in both cases, while near r/a=0.92, a dramatic reversal of the poloidal flow of turbulence relative to the core flow direction is observed in plasmas with the ion {del}B drift pointing towards the divertor X-point. No such flow reversal is observed in plasmas with the ion {del}B drift pointing away from the divertor X-point. This poloidal flow reversal results in a significantly larger local shear in the poloidal turbulence flow velocity in plasmas with the ion {del}B drift pointing towards the divertor X-point. Additionally, these plasmas locally exhibit significant dispersion, with two distinct and counter-propagating turbulence modes. Likewise, the radial correlation length of the turbulence is reduced in these plasmas, consistent with biorthogonal decomposition measurements of dominant turbulence structures. The naturally occurring turbulence flow shear in these LSN plasmas may facilitate the LH transition that occurs at an input power of roughly one-half to one-third that of corresponding plasmas with the ion {del}B drift pointing away from the X-point.},
doi = {},
journal = {},
number = ,
volume = ,
place = {United States},
year = {2003},
month = {7}
}