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High-field side scrape-off layer investigation: Plasma profiles and impurity screening behavior in near-double-null configurations

Journal Article · · Nuclear Materials and Energy
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  1. Massachusetts Inst. of Technology (MIT), Cambridge, MA (United States). Plasma Science and Fusion Center; OSTI
  2. Massachusetts Inst. of Technology (MIT), Cambridge, MA (United States). Plasma Science and Fusion Center
  3. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
+ Show Author Affiliations
New experiments on Alcator C-Mod reveal that the favorable impurity screening characteristics of the high-field side (HFS) scrape-off layer (SOL), previously reported for single null geometries, is retained in double null configurations, despite the formation of an extremely thin SOL. In balanced double-null, nitrogen injected locally into the HFS SOL is better screened by a factor of 2.5 compared to the same injection into the low field side (LFS) SOL. This result is insensitive to plasma current and Greenwald fraction. Nitrogen injected into the HFS SOL is not as well screened (only a factor of 1.5 improvement over LFS) in unbalanced double-null discharges, when the primary divertor is in the direction of B×∇B. In this configuration, impurity ‘plume’ emission patterns indicate that an opposing E × B drift competes with the parallel impurity flow to the divertor. In balanced double-null plasmas, the dispersal pattern exhibits a dominant E × B motion. Unbalanced discharges with the primary divertor opposite the direction of B×∇B exhibit excellent HFS screening characteristics – a factor of 5 enhancement compared to LFS. These data support the idea that future tokamaks should locate all RF actuators and close-fitting wall structures on the HFS and employ near-double-null magnetic topologies, both to precisely control plasma conditions at the antenna/plasma interface and to maximally mitigate the impact of local impurity sources arising from plasma-material interactions.
Research Organization:
Massachusetts Inst. of Technology (MIT), Cambridge, MA (United States). Plasma Science and Fusion Center
Sponsoring Organization:
USDOE Office of Science (SC), Fusion Energy Sciences (FES)
Grant/Contract Number:
FC02-99ER54512
OSTI ID:
1894461
Alternate ID(s):
OSTI ID: 22834650
Journal Information:
Nuclear Materials and Energy, Journal Name: Nuclear Materials and Energy Vol. 12; ISSN 2352-1791
Publisher:
ElsevierCopyright Statement
Country of Publication:
United States
Language:
English

References (19)

Local impurity puffing as a scrape-off layer diagnostic on the Alcator C-Mod tokamak journal February 1997
The lower hybrid current drive system for steady-state operation of the Vulcan tokamak conceptual design journal March 2012
ARC: A compact, high-field, fusion nuclear science facility and demonstration power plant with demountable magnets journal November 2015
Plasma profiles and flows in the high-field side scrape-off layer in Alcator C-Mod journal March 2005
Mirror Langmuir probe: A technique for real-time measurement of magnetized plasma conditions using a single Langmuir electrode journal July 2007
Time-resolved x-ray and extreme ultraviolate spectrometer for use on the National Spherical Torus Experiment journal October 2008
Wall scanning probe for high-field side plasma measurements on Alcator C-Mod journal February 2009
High confinement/high radiated power H-mode experiments in Alcator C-Mod and consequences for International Thermonuclear Experimental Reactor (ITER) Q DT  = 10 operation journal May 2011
New insights on boundary plasma turbulence and the quasi-coherent mode in Alcator C-Mod using a Mirror Langmuir Probe journal May 2014
First results from Alcator‐C‐MOD* journal May 1994
Impurity screening in Ohmic and high confinement (H-mode) plasmas in the Alcator C-Mod tokamak journal May 1997
Transport-driven Scrape-Off-Layer flows and the boundary conditions imposed at the magnetic separatrix in a tokamak plasma journal September 2004
Heuristic drift-based model of the power scrape-off width in low-gas-puff H-mode tokamaks journal December 2011
Transport and drift-driven plasma flow components in the Alcator C-Mod boundary plasma journal January 2013
Scaling of the tokamak near the scrape-off layer H-mode power width and implications for ITER journal August 2013
ADX: a high field, high power density, advanced divertor and RF tokamak journal April 2015
Density limits in toroidal plasmas journal July 2002
Impurity plume experiments in the edge plasma of the Alcator C-Mod tokamak journal September 2004
Interpretation of the D   emission from the high field side of Alcator C-Mod journal June 2004

Cited By (3)

Poloidal asymmetry in the narrow heat flux feature in the TCV scrape-off layer journal June 2017
Blob velocity scaling in diverted tokamaks: A comparison between theory and simulation journal March 2019
High field side lower hybrid wave launch for steady state plasma sustainment journal November 2018

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Related Subjects

70 PLASMA PHYSICS AND FUSION TECHNOLOGY
Alcator C-Mod
Double null
High field side scrape-off layer
Impurity screening