First results from the Thomson scattering diagnostic on proto-MPEX

T. M. Biewer, S. Meitner, J. Rapp, H. Ray, G. Shaw

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Abstract

A Thomson scattering (TS) diagnostic has been successfully implemented on the prototype Material Plasma Exposure eXperiment (Proto-MPEX) at Oak Ridge National Laboratory. The diagnostic collects the light scattered by plasma electrons and spectroscopically resolves the Doppler shift imparted to the light by the velocity of the electrons. The spread in velocities is proportional to the electron temperature, while the total number of photons is proportional to the electron density. TS is a technique used on many devices to measure the electron temperature (Te) and electron density (ne) of the plasma. A challenging aspect of the technique is to discriminate the small number of Thomson scattered photons against the large peak of background photons from the high-power laser used to probe the plasma. A variety of methods are used to mitigate the background photons in Proto-MPEX, including Brewster angled windows, viewing dumps, and light baffles. With these methods, first results were measured from argon plasmas in Proto-MPEX, indicating Te ∼ 2 eV and ne ∼ 1 × 1019 m-3. The configuration of the Proto-MPEX TS diagnostic will be described and plans for improvement will be given.

Original languageEnglish
Article number11E518
JournalReview of Scientific Instruments
Volume87
Issue number11
DOIs
StatePublished - Nov 1 2016

Funding

This work was supported by the U.S. D.O.E Contract No. DE-AC05-00OR22725. Research sponsored by the Laboratory Directed Research and Development Program of Oak Ridge National Laboratory, managed by UT-Battelle, LLC, for the U.S. Department of Energy.

FundersFunder number
U.S. Department of Energy
Oak Ridge National Laboratory

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