Diagnostic options for radiative divertor feedback control on NSTX-U

Journal Article · Mon Oct 15 00:00:00 EDT 2012 · Review of Scientific Instruments

DOI:https://doi.org/10.1063/1.4732176· OSTI ID:22093858

Soukhanovskii, V. A.; McLean, A. G. ^[1]; Gerhardt, S. P.; Kaita, R. ^[2]; Raman, R. ^[3]

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1. Lawrence Livermore National Laboratory, Livermore, California, 94550 (United States)
2. Princeton Plasma Physics Laboratory, Princeton, New Jersey 08540 (United States)
3. University of Washington, Seattle, Washington 98195 (United States)

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 (q{sub peak} Less-Than-Or-Slanted-Equal-To 15 MW/m{sup 2}), radiative divertor experiments have demonstrated a significant reduction of divertor peak heat flux simultaneously with good core H-mode confinement using pre-programmed D{sub 2} or CD{sub 4} 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{sup 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).

• OSTI ID: 22093858
• Journal Information: Review of Scientific Instruments, Vol. 83, Issue 10; Other Information: (c) 2012 American Institute of Physics; Country of input: International Atomic Energy Agency (IAEA); ISSN 0034-6748
• Country of Publication: United States
• Language: English

Related Subjects

70 PLASMA PHYSICS AND FUSION TECHNOLOGY
46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND TECHNOLOGY
CONTROL SYSTEMS
DAMAGE
DEUTERIUM
DIVERTORS
FEEDBACK
FIRST WALL
GAS INJECTION
GRAPHITE
HEAT FLUX
HEATING LOAD
H-MODE PLASMA CONFINEMENT
IMPURITIES
INFRARED THERMOGRAPHY
ITER TOKAMAK
NSTX DEVICE
PLASMA
PLASMA DIAGNOSTICS
PLASMA SCRAPE-OFF LAYER
RECOMBINATION
SPHERICAL CONFIGURATION
STEADY-STATE CONDITIONS
SURFACES