Electron density measurements in the National Spherical Torus Experiment detached divertor region using Stark broadening of deuterium infrared Paschen emission lines

Journal Article · Sun Oct 15 00:00:00 EDT 2006 · Review of Scientific Instruments

DOI:https://doi.org/10.1063/1.2336456· OSTI ID:20861325

Soukhanovskii, V A; Johnson, D W; Kaita, R; Roquemore, A L ^[1]

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1. Lawrence Livermore National Laboratory, Livermore, California 94550 (United States)

Spatially resolved measurements of deuterium Balmer and Paschen line emission have been performed in the divertor region of the National Spherical Torus Experiment using a commercial 0.5 m Czerny-Turner spectrometer. While the Balmer emission lines, as well as the Balmer and Paschen continua in the ultraviolet and visible regions have been extensively used for tokamak divertor plasma temperature and density measurements, the diagnostic potential of infrared Paschen lines has been largely overlooked. We analyze Stark broadening of the lines corresponding to 2-n and 3-m transitions with principal quantum numbers n=7-12 and m=10-12 using recent model microfield method calculations [C. Stehle and R. Hutcheon, Astron. Astrophys., Suppl. Ser. 140, 93 (1999)]. Densities in the range (5-50)x10{sup 19} m{sup -3} are obtained in the recombining inner divertor plasma in 2-6 MW neutral beam heated H-mode discharges. The measured Paschen line profiles show good sensitivity to Stark effects and low sensitivity to instrumental and Doppler broadenings. The lines are situated in the near-infrared wavelength domain, where optical signal extraction schemes for harsh nuclear environments are practically realizable and where a recombining divertor plasma is optically thin. These properties make them an attractive recombining divertor density diagnostic for a burning plasma experiment.

• OSTI ID: 20861325
• Journal Information: Review of Scientific Instruments, Vol. 77, Issue 10; Other Information: DOI: 10.1063/1.2336456; (c) 2006 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
DEUTERIUM
DIVERTORS
DOPPLER BROADENING
ELECTRON DENSITY
ELECTRON TEMPERATURE
EMISSION
H-MODE PLASMA CONFINEMENT
ION TEMPERATURE
PASCHEN LINES
PLASMA
PLASMA BEAM INJECTION
PLASMA DENSITY
PLASMA DIAGNOSTICS
QUANTUM NUMBERS
SPECTROMETERS
STARK EFFECT
TOKAMAK DEVICES
ULTRAVIOLET RADIATION
VISIBLE RADIATION