A high-power spatial filter for Thomson scattering stray light reduction

Journal Article · Tue Mar 15 04:00:00 EDT 2011 · Review of Scientific Instruments

DOI:https://doi.org/10.1063/1.3549142· OSTI ID:22062271

Levesque, J P; Litzner, K D; Mauel, M E; Maurer, D A; Navratil, G A; Pedersen, T S ^[1]

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1. Department of Applied Physics and Applied Mathematics, Columbia University, 500 W. 120th Street, New York, New York 10027 (United States)

The Thomson scattering diagnostic on the High Beta Tokamak-Extended Pulse (HBT-EP) is routinely used to measure electron temperature and density during plasma discharges. Avalanche photodiodes in a five-channel interference filter polychromator measure scattered light from a 6 ns, 800 mJ, 1064 nm Nd:YAG laser pulse. A low cost, high-power spatial filter was designed, tested, and added to the laser beamline in order to reduce stray laser light to levels which are acceptable for accurate Rayleigh calibration. A detailed analysis of the spatial filter design and performance is given. The spatial filter can be easily implemented in an existing Thomson scattering system without the need to disturb the vacuum chamber or significantly change the beamline. Although apertures in the spatial filter suffer substantial damage from the focused beam, with proper design they can last long enough to permit absolute calibration.

• OSTI ID: 22062271
• Journal Information: Review of Scientific Instruments, Journal Name: Review of Scientific Instruments Journal Issue: 3 Vol. 82; ISSN 0034-6748; ISSN RSINAK
• Country of Publication: United States
• Language: English

Related Subjects

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND TECHNOLOGY
70 PLASMA PHYSICS AND FUSION TECHNOLOGY
BEAMS
CALIBRATION
COLUMBIA HIGH-BETA TOKAMAK
ELECTRIC DISCHARGES
ELECTRON DENSITY
ELECTRON TEMPERATURE
HIGH-BETA PLASMA
INTERFERENCE
LIGHT TRANSMISSION
NEODYMIUM LASERS
PERFORMANCE
PHOTODIODES
THOMSON SCATTERING
VISIBLE RADIATION