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Title: Divertor Heat Flux Mitigation in High-Performance H-mode Discharges in the National Spherical Torus Experiment.

Abstract

Experiments conducted in high-performance 1.0 MA and 1.2 MA 6 MW NBI-heated H-mode discharges with a high magnetic flux expansion radiative divertor in NSTX demonstrate that significant divertor peak heat flux reduction and access to detachment may be facilitated naturally in a highly-shaped spherical torus (ST) configuration. Improved plasma performance with high {beta}{sub t} = 15-25%, a high bootstrap current fraction f{sub BS} = 45-50%, longer plasma pulses, and an H-mode regime with smaller ELMs has been achieved in the strongly-shaped lower single null configuration with elongation {kappa} = 2.2-2.4 and triangularity {delta} = 0.6-0.8. Divertor peak heat fluxes were reduced from 6-12 MW/m{sup 2} to 0.5-2 MW/m{sup 2} in ELMy H-mode discharges using the inherently high magnetic flux expansion f{sub m} = 16-25 and the partial detachment of the outer strike point at several D{sub 2} injection rates. A good core confinement and pedestal characteristics were maintained, while the core carbon concentration and the associated Z{sub eff} were reduced. The partially detached divertor regime was characterized by an increase in divertor radiated power, a reduction of ion flux to the plate, and a large neutral compression ratio. Spectroscopic measurements indicated a formation of a high-density, low temperature region adjacentmore » to the outer strike point, where substantial increases in the volume recombination rate and CII, CIII emission rates was measured.« less

Authors:
; ; ;
Publication Date:
Research Org.:
Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
Sponsoring Org.:
USDOE
OSTI Identifier:
965081
Report Number(s):
LLNL-JRNL-409668
Journal ID: ISSN 0029-5515; TRN: US0903575
DOE Contract Number:  
W-7405-ENG-48
Resource Type:
Journal Article
Journal Name:
Nuclear Fusion
Additional Journal Information:
Journal Volume: 49; Journal ID: ISSN 0029-5515
Country of Publication:
United States
Language:
English
Subject:
70 PLASMA PHYSICS AND FUSION; BOOTSTRAP CURRENT; CARBON; COMPRESSION RATIO; CONFIGURATION; CONFINEMENT; DIVERTORS; ELONGATION; HEAT FLUX; MAGNETIC FLUX; MITIGATION; PERFORMANCE; PLASMA; RECOMBINATION

Citation Formats

Soukhanovskii, V A, Maingi, R, Gates, D, and Menard, J. Divertor Heat Flux Mitigation in High-Performance H-mode Discharges in the National Spherical Torus Experiment.. United States: N. p., 2008. Web.
Soukhanovskii, V A, Maingi, R, Gates, D, & Menard, J. Divertor Heat Flux Mitigation in High-Performance H-mode Discharges in the National Spherical Torus Experiment.. United States.
Soukhanovskii, V A, Maingi, R, Gates, D, and Menard, J. Wed . "Divertor Heat Flux Mitigation in High-Performance H-mode Discharges in the National Spherical Torus Experiment.". United States. https://www.osti.gov/servlets/purl/965081.
@article{osti_965081,
title = {Divertor Heat Flux Mitigation in High-Performance H-mode Discharges in the National Spherical Torus Experiment.},
author = {Soukhanovskii, V A and Maingi, R and Gates, D and Menard, J},
abstractNote = {Experiments conducted in high-performance 1.0 MA and 1.2 MA 6 MW NBI-heated H-mode discharges with a high magnetic flux expansion radiative divertor in NSTX demonstrate that significant divertor peak heat flux reduction and access to detachment may be facilitated naturally in a highly-shaped spherical torus (ST) configuration. Improved plasma performance with high {beta}{sub t} = 15-25%, a high bootstrap current fraction f{sub BS} = 45-50%, longer plasma pulses, and an H-mode regime with smaller ELMs has been achieved in the strongly-shaped lower single null configuration with elongation {kappa} = 2.2-2.4 and triangularity {delta} = 0.6-0.8. Divertor peak heat fluxes were reduced from 6-12 MW/m{sup 2} to 0.5-2 MW/m{sup 2} in ELMy H-mode discharges using the inherently high magnetic flux expansion f{sub m} = 16-25 and the partial detachment of the outer strike point at several D{sub 2} injection rates. A good core confinement and pedestal characteristics were maintained, while the core carbon concentration and the associated Z{sub eff} were reduced. The partially detached divertor regime was characterized by an increase in divertor radiated power, a reduction of ion flux to the plate, and a large neutral compression ratio. Spectroscopic measurements indicated a formation of a high-density, low temperature region adjacent to the outer strike point, where substantial increases in the volume recombination rate and CII, CIII emission rates was measured.},
doi = {},
url = {https://www.osti.gov/biblio/965081}, journal = {Nuclear Fusion},
issn = {0029-5515},
number = ,
volume = 49,
place = {United States},
year = {2008},
month = {12}
}