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Title: Thomson scattering density calibration by Rayleigh and rotational Raman scattering on NSTX

Abstract

The multipoint Thomson scattering diagnostic measures the profiles of the electron temperature T{sub e}(R) and density n{sub e}(R) on the horizontal midplane of NSTX. Normal operation makes use of Rayleigh scattering in nitrogen or argon to derive the density profile. While the Rayleigh scattering n{sub e}(R) calibration has been validated by comparison to other density measurements and through its correlation with plasma phenomena, it does require dedicated detectors at the laser wavelength in this filter polychromator based diagnostic. The presence of dust and/or stray laser light precludes routine use of these dedicated spectral channels for Thomson scattering measurement. Hence it is of interest to investigate the use of Raman scattering in nitrogen for the purpose of density calibration since it could free up detection equipment, which could then be used for the instrumentation of additional radial channels. In this paper the viewing optics 'geometrical factor' profiles obtained from Rayleigh and Raman scattering are compared. While both techniques agree nominally, residual effects on the order of 10% remain and will be discussed.

Authors:
 [1]
  1. Princeton Plasma Physics Laboratory, Princeton, New Jersey 08543 (United States)
Publication Date:
OSTI Identifier:
21266560
Resource Type:
Journal Article
Journal Name:
Review of Scientific Instruments
Additional Journal Information:
Journal Volume: 79; Journal Issue: 10; Other Information: DOI: 10.1063/1.2956747; (c) 2008 American Institute of Physics; Country of input: International Atomic Energy Agency (IAEA); Journal ID: ISSN 0034-6748
Country of Publication:
United States
Language:
English
Subject:
70 PLASMA PHYSICS AND FUSION TECHNOLOGY; ARGON; CALIBRATION; COMPARATIVE EVALUATIONS; ELECTRON DENSITY; ELECTRON TEMPERATURE; FILTERS; NITROGEN; NSTX DEVICE; OPTICS; RAMAN EFFECT; RAMAN SPECTRA; RAYLEIGH SCATTERING; STEADY-STATE CONDITIONS; THOMSON SCATTERING

Citation Formats

LeBlanc, B P. Thomson scattering density calibration by Rayleigh and rotational Raman scattering on NSTX. United States: N. p., 2008. Web. doi:10.1063/1.2956747.
LeBlanc, B P. Thomson scattering density calibration by Rayleigh and rotational Raman scattering on NSTX. United States. doi:10.1063/1.2956747.
LeBlanc, B P. Wed . "Thomson scattering density calibration by Rayleigh and rotational Raman scattering on NSTX". United States. doi:10.1063/1.2956747.
@article{osti_21266560,
title = {Thomson scattering density calibration by Rayleigh and rotational Raman scattering on NSTX},
author = {LeBlanc, B P},
abstractNote = {The multipoint Thomson scattering diagnostic measures the profiles of the electron temperature T{sub e}(R) and density n{sub e}(R) on the horizontal midplane of NSTX. Normal operation makes use of Rayleigh scattering in nitrogen or argon to derive the density profile. While the Rayleigh scattering n{sub e}(R) calibration has been validated by comparison to other density measurements and through its correlation with plasma phenomena, it does require dedicated detectors at the laser wavelength in this filter polychromator based diagnostic. The presence of dust and/or stray laser light precludes routine use of these dedicated spectral channels for Thomson scattering measurement. Hence it is of interest to investigate the use of Raman scattering in nitrogen for the purpose of density calibration since it could free up detection equipment, which could then be used for the instrumentation of additional radial channels. In this paper the viewing optics 'geometrical factor' profiles obtained from Rayleigh and Raman scattering are compared. While both techniques agree nominally, residual effects on the order of 10% remain and will be discussed.},
doi = {10.1063/1.2956747},
journal = {Review of Scientific Instruments},
issn = {0034-6748},
number = 10,
volume = 79,
place = {United States},
year = {2008},
month = {10}
}