A two photon absorption laser induced fluorescence diagnostic for fusion plasmas

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

DOI:https://doi.org/10.1063/1.4728092· OSTI ID:22093847

Magee, R. M.; Galante, M. E.; McCarren, D.; Scime, E. E. ^[1]; Boivin, R. L.; Brooks, N. H.; Groebner, R. J.; Hill, D. N. ^[2]; Porter, G. D. ^[3]

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1. Physics Department, West Virginia University, Morgantown, West Virginia 26506 (United States)
2. General Atomics, San Diego, California 92121 (United States)
3. Lawrence Livermore National Laboratory, Livermore, California 94550 (United States)

The quality of plasma produced in a magnetic confinement fusion device is influenced to a large extent by the neutral gas surrounding the plasma. The plasma is fueled by the ionization of neutrals, and charge exchange interactions between edge neutrals and plasma ions are a sink of energy and momentum. Here we describe a diagnostic capable of measuring the spatial distribution of neutral gas in a magnetically confined fusion plasma. A high intensity (5 MW/cm{sup 2}), narrow bandwidth (0.1 cm{sup -1}) laser is injected into a hydrogen plasma to excite the Lyman {beta} transition via the simultaneous absorption of two 205 nm photons. The absorption rate, determined by measurement of subsequent Balmer {alpha} emission, is proportional to the number of particles with a given velocity. Calibration is performed in situ by filling the chamber to a known pressure of neutral krypton and exciting a transition close in wavelength to that used in hydrogen. We present details of the calibration procedure, including a technique for identifying saturation broadening, measurements of the neutral density profile in a hydrogen helicon plasma, and discuss the application of the diagnostic to plasmas in the DIII-D tokamak.

• OSTI ID: 22093847
• 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
ABSORPTION
CALIBRATION
CHARGE-EXCHANGE INTERACTIONS
DENSITY
DOUBLET-3 DEVICE
FLUORESCENCE
IONS
KRYPTON
LASER RADIATION
MAGNETIC CONFINEMENT
MULTI-PHOTON PROCESSES
PHOTONS
PLASMA
PLASMA BEAM INJECTION
PLASMA DENSITY
PLASMA DIAGNOSTICS
SPATIAL DISTRIBUTION
TOKAMAK DEVICES
VELOCITY
WAVELENGTHS