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Title: Diagnostic options for radiative divertor feedback control on NSTX-U

Abstract

A radiative divertor technique is used in present tokamak experiments and planned for ITER to mitigate high heat loads on divertor plasma-facing components (PFCs) to prevent excessive material erosion and thermal damage. In NSTX, a large spherical tokamak with lithium-coated graphite PFCs and high divertor heat flux (qpeak ≤ 15 MW/m2), radiative divertor experiments have demonstrated a significant reduction of divertor peak heat flux simultaneously with good core H-mode confinement using pre-programmed D2 or CD4 gas injections. In this work diagnostic options for a new real-time feedback control system for active radiative divertor detachment control in NSTX-U, where steady-state peak divertor heat fluxes are projected to reach 20–30 MW/m 2, are discussed. Based on the NSTX divertor detachment measurements and analysis, the control diagnostic signals available for NSTX-U include divertor radiated power, neutral pressure, spectroscopic deuterium recombination signatures, infrared thermography of PFC surfaces, and thermoelectric scrape-off layer current. In addition, spectroscopic “security” monitoring of possible confinement or pedestal degradation is recommended. These signals would be implemented in a digital plasma control system to manage the divertor detachment process via an actuator (impurity gas seeding rate).

Authors:
; ; ; ;
Publication Date:
Research Org.:
Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
Sponsoring Org.:
USDOE
OSTI Identifier:
1089528
Report Number(s):
LLNL-JRNL-555821
Journal ID: ISSN 0034-6748
DOE Contract Number:  
W-7405-ENG-48
Resource Type:
Journal Article
Journal Name:
Review of Scientific Instruments
Additional Journal Information:
Journal Volume: 83; Journal Issue: 10; Journal ID: ISSN 0034-6748
Publisher:
American Institute of Physics (AIP)
Country of Publication:
United States
Language:
English
Subject:
74 ATOMIC AND MOLECULAR PHYSICS; 70 PLASMA PHYSICS AND FUSION

Citation Formats

Soukhanovskii, V. A., Gerhardt, S. P., Kaita, R., McLean, A. G., and Raman, R. Diagnostic options for radiative divertor feedback control on NSTX-U. United States: N. p., 2012. Web. doi:10.1063/1.4732176.
Soukhanovskii, V. A., Gerhardt, S. P., Kaita, R., McLean, A. G., & Raman, R. Diagnostic options for radiative divertor feedback control on NSTX-U. United States. doi:10.1063/1.4732176.
Soukhanovskii, V. A., Gerhardt, S. P., Kaita, R., McLean, A. G., and Raman, R. Mon . "Diagnostic options for radiative divertor feedback control on NSTX-U". United States. doi:10.1063/1.4732176. https://www.osti.gov/servlets/purl/1089528.
@article{osti_1089528,
title = {Diagnostic options for radiative divertor feedback control on NSTX-U},
author = {Soukhanovskii, V. A. and Gerhardt, S. P. and Kaita, R. and McLean, A. G. and Raman, R.},
abstractNote = {A radiative divertor technique is used in present tokamak experiments and planned for ITER to mitigate high heat loads on divertor plasma-facing components (PFCs) to prevent excessive material erosion and thermal damage. In NSTX, a large spherical tokamak with lithium-coated graphite PFCs and high divertor heat flux (qpeak ≤ 15 MW/m2), radiative divertor experiments have demonstrated a significant reduction of divertor peak heat flux simultaneously with good core H-mode confinement using pre-programmed D2 or CD4 gas injections. In this work diagnostic options for a new real-time feedback control system for active radiative divertor detachment control in NSTX-U, where steady-state peak divertor heat fluxes are projected to reach 20–30 MW/m2, are discussed. Based on the NSTX divertor detachment measurements and analysis, the control diagnostic signals available for NSTX-U include divertor radiated power, neutral pressure, spectroscopic deuterium recombination signatures, infrared thermography of PFC surfaces, and thermoelectric scrape-off layer current. In addition, spectroscopic “security” monitoring of possible confinement or pedestal degradation is recommended. These signals would be implemented in a digital plasma control system to manage the divertor detachment process via an actuator (impurity gas seeding rate).},
doi = {10.1063/1.4732176},
journal = {Review of Scientific Instruments},
issn = {0034-6748},
number = 10,
volume = 83,
place = {United States},
year = {2012},
month = {10}
}