skip to main content
OSTI.GOV title logo U.S. Department of Energy
Office of Scientific and Technical Information

Title: Transport in the tokamak plasma edge

Abstract

Experimental observations characterize the edge plasma or boundary layer in magnetically confined plasmas as a region of great complexity. Evidence suggests the edge physics plays a key role in plasma confinement although the mechanism remains unresolved. This study focuses on issues in two areas: observed poloidal asymmetries in the Scrape Off Layer (SOL) edge plasma and the physical nature of the plasma-neutral recycling. A computational model solves the coupled two dimensional partial differential equations governing the plasma fluid density, parallel and radial velocities, electron and ion temperatures and neutral density under assumptions of toroidal symmetry, ambipolarity, anomalous diffusive radial flux, and neutral-ion thermal equilibrium. Drift flow and plasma potential are calculated as dependent quantities. Computational results are compared to experimental data for the CCT and TEXTOR:ALT-II tokamak limiter cases. Comparisons show drift flux is a major component of the poloidal flow in the SOL along the tangency/separatrix. Plasma-neutral recycling is characterized in several tokamak divertors, including the C-MOD device using magnetic flux surface coordinates. Recycling is characterized by time constant, {tau}{sub rc}, on the order of tens of milliseconds. Heat flux transients from the core into the edge on shorter time scales significantly increase the plasma temperatures at the targetmore » and may increase sputtering. Recycling conditions in divertors vary considerably depending on recycled flux to the core. The high density, low temperature solution requires that the neutral mean free path be small compared to the divertor target to x-point distance. The simulations and analysis support H-mode confinement and transition models based on the recycling divertor solution bifurcation.« less

Authors:
Publication Date:
Research Org.:
California Univ., Los Angeles, CA (USA)
OSTI Identifier:
5829371
Resource Type:
Miscellaneous
Resource Relation:
Other Information: Thesis (Ph. D.)
Country of Publication:
United States
Language:
English
Subject:
70 PLASMA PHYSICS AND FUSION TECHNOLOGY; H-MODE PLASMA CONFINEMENT; PLASMA SIMULATION; ASYMMETRY; COMPARATIVE EVALUATIONS; EDGE LOCALIZED MODES; ELECTRON TEMPERATURE; GEOMETRY; HEAT FLUX; ION TEMPERATURE; LIMITERS; MAGNETIC CONFINEMENT; PLASMA CONFINEMENT; PLASMA DENSITY; PLASMA DRIFT; PLASMA SCRAPE-OFF LAYER; POLOIDAL FIELD DIVERTORS; SPUTTERING; TEXTOR TOKAMAK; BOUNDARY LAYERS; CLOSED PLASMA DEVICES; CONFINEMENT; DIVERTORS; INSTABILITY; LAYERS; MATHEMATICS; PLASMA INSTABILITY; PLASMA MACROINSTABILITIES; SIMULATION; THERMONUCLEAR DEVICES; TOKAMAK DEVICES; 700101* - Fusion Energy- Plasma Research- Confinement, Heating, & Production

Citation Formats

Vold, E L. Transport in the tokamak plasma edge. United States: N. p., 1989. Web.
Vold, E L. Transport in the tokamak plasma edge. United States.
Vold, E L. 1989. "Transport in the tokamak plasma edge". United States.
@article{osti_5829371,
title = {Transport in the tokamak plasma edge},
author = {Vold, E L},
abstractNote = {Experimental observations characterize the edge plasma or boundary layer in magnetically confined plasmas as a region of great complexity. Evidence suggests the edge physics plays a key role in plasma confinement although the mechanism remains unresolved. This study focuses on issues in two areas: observed poloidal asymmetries in the Scrape Off Layer (SOL) edge plasma and the physical nature of the plasma-neutral recycling. A computational model solves the coupled two dimensional partial differential equations governing the plasma fluid density, parallel and radial velocities, electron and ion temperatures and neutral density under assumptions of toroidal symmetry, ambipolarity, anomalous diffusive radial flux, and neutral-ion thermal equilibrium. Drift flow and plasma potential are calculated as dependent quantities. Computational results are compared to experimental data for the CCT and TEXTOR:ALT-II tokamak limiter cases. Comparisons show drift flux is a major component of the poloidal flow in the SOL along the tangency/separatrix. Plasma-neutral recycling is characterized in several tokamak divertors, including the C-MOD device using magnetic flux surface coordinates. Recycling is characterized by time constant, {tau}{sub rc}, on the order of tens of milliseconds. Heat flux transients from the core into the edge on shorter time scales significantly increase the plasma temperatures at the target and may increase sputtering. Recycling conditions in divertors vary considerably depending on recycled flux to the core. The high density, low temperature solution requires that the neutral mean free path be small compared to the divertor target to x-point distance. The simulations and analysis support H-mode confinement and transition models based on the recycling divertor solution bifurcation.},
doi = {},
url = {https://www.osti.gov/biblio/5829371}, journal = {},
number = ,
volume = ,
place = {United States},
year = {Sun Jan 01 00:00:00 EST 1989},
month = {Sun Jan 01 00:00:00 EST 1989}
}

Miscellaneous:
Other availability
Please see Document Availability for additional information on obtaining the full-text document. Library patrons may search WorldCat to identify libraries that may hold this item.

Save / Share: