Identification and mitigation of stray laser light in the Thomson scattering system on the Madison Symmetric Torus (MST)
- Department of Physics, University of Wisconsin–Madison, 1150 University Avenue, Madison, Wisconsin 53706 (United States)
The Thomson scattering diagnostic on the Madison Symmetric Torus (MST) records excessive levels of stray Nd:YAG laser light. Stray light saturates the 1064 nm spectral channel in all polychromators, which prevents absolute electron density measurements via Rayleigh scattering calibration. Furthermore, stray light contaminates adjacent spectral channels for r/a ≥ 0.75, which renders the diagnostic unable to make electron temperature measurements at these radii. In situ measurements of stray light levels during a vacuum vessel vent are used to identify stray light sources and strategies for reduction of stray light levels. Numerical modeling using Zemax OpticStudio supports these measurements. The model of the vacuum vessel and diagnostic includes synthetic collection optics to enable direct comparison of measured and simulated stray light levels. Modeling produces qualitatively similar stray light distributions to MST measurements, and quantifies the mitigation effects of stray light mitigation strategies prior to implementation.
- OSTI ID:
- 22596583
- Journal Information:
- Review of Scientific Instruments, Vol. 87, Issue 11; Other Information: (c) 2016 Author(s); Country of input: International Atomic Energy Agency (IAEA); ISSN 0034-6748
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
CALIBRATION
COMPARATIVE EVALUATIONS
DISTRIBUTION
ELECTRON DENSITY
ELECTRON TEMPERATURE
ELECTRONS
IMPLEMENTATION
LIGHT SOURCES
MITIGATION
NEODYMIUM LASERS
OPTICS
RAYLEIGH SCATTERING
REDUCTION
SIMULATION
SYMMETRY
TEMPERATURE MEASUREMENT
THOMSON SCATTERING