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Title: Space-resolved extreme ultraviolet spectrometer for impurity emission profile measurement in Large Helical Device

Abstract

A space-resolved extreme ultraviolet (EUV) spectrometer working in 60-400 A range has been developed to observe impurity emission profiles in core and edge plasmas of Large Helical Device (LHD). A flat focus is made for plane surface detector by using a varied line spacing holographic grating with an angle of incidence of 87 deg. An excellent spectral resolution of 0.22 A at 200 A is then obtained after careful adjustment of the optical components. In the profile measurement of the LHD plasmas, the toroidal resolution is important as well as the radial resolution because the magnetic surfaces of LHD quickly change when the observation chord is tilted at a slightly different toroidal location. Horizontal dispersion is therefore selected for the present spectrometer. As a result, the toroidal resolution of 75 mm is achieved at the plasma position. An enough radial resolution of 10 mm is also obtained at spatial-resolution slit width of 0.2 mm. In order to measure the full radial profile of LHD plasmas the spectrometer is placed at a distance of {approx}9200 mm away from the plasma center and a backilluminated charge-coupled device with a size of 6.6x26.6 mm{sup 2} is set vertical to the horizontal dispersion. Halfmore » of the LHD plasma, i.e., {approx}50 cm, can be measured along the vertical direction at horizontally elongated plasma cross section. A full vertical profile can be obtained by changing the vertical angle of the EUV spectrometer. As an example the full vertical profile of edge C IV (312.4 A) emission is presented. A wavelength interval of 35-65 A can be simultaneously observed, which varies according to the wavelength to be measured. A local emission profile of Fe XX (132.67 A) is also presented after Abel inversion as a typical example of the core EUV emission. Finally, the EUV spectrometer is absolutely calibrated using EUV bremsstrahlung continuum profile in comparison with absolute values of visible bremsstrahlung continuum profile because the bremsstrahlung continuum can be easily detected in high-density discharges of LHD.« less

Authors:
;  [1]; ;  [2]
  1. Department of Fusion Science, Graduate University for Advanced Studies, Toki, Gifu 509-5292 (Japan)
  2. National Institute for Fusion Science, Toki, Gifu 509-5292 (Japan)
Publication Date:
OSTI Identifier:
22053939
Resource Type:
Journal Article
Journal Name:
Review of Scientific Instruments
Additional Journal Information:
Journal Volume: 81; Journal Issue: 3; Other Information: (c) 2010 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:
46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND TECHNOLOGY; 70 PLASMA PHYSICS AND FUSION TECHNOLOGY; BREMSSTRAHLUNG; CHARGE-COUPLED DEVICES; EXTREME ULTRAVIOLET RADIATION; GRATINGS; HOLOGRAPHY; INCIDENCE ANGLE; LHD DEVICE; MAGNETIC SURFACES; PLASMA; SPATIAL RESOLUTION; ULTRAVIOLET SPECTROMETERS; VISIBLE RADIATION; WAVELENGTHS

Citation Formats

Chunfeng, Dong, Hangyu, Zhou, Morita, Shigeru, and Goto, Motoshi. Space-resolved extreme ultraviolet spectrometer for impurity emission profile measurement in Large Helical Device. United States: N. p., 2010. Web. doi:10.1063/1.3299060.
Chunfeng, Dong, Hangyu, Zhou, Morita, Shigeru, & Goto, Motoshi. Space-resolved extreme ultraviolet spectrometer for impurity emission profile measurement in Large Helical Device. United States. https://doi.org/10.1063/1.3299060
Chunfeng, Dong, Hangyu, Zhou, Morita, Shigeru, and Goto, Motoshi. 2010. "Space-resolved extreme ultraviolet spectrometer for impurity emission profile measurement in Large Helical Device". United States. https://doi.org/10.1063/1.3299060.
@article{osti_22053939,
title = {Space-resolved extreme ultraviolet spectrometer for impurity emission profile measurement in Large Helical Device},
author = {Chunfeng, Dong and Hangyu, Zhou and Morita, Shigeru and Goto, Motoshi},
abstractNote = {A space-resolved extreme ultraviolet (EUV) spectrometer working in 60-400 A range has been developed to observe impurity emission profiles in core and edge plasmas of Large Helical Device (LHD). A flat focus is made for plane surface detector by using a varied line spacing holographic grating with an angle of incidence of 87 deg. An excellent spectral resolution of 0.22 A at 200 A is then obtained after careful adjustment of the optical components. In the profile measurement of the LHD plasmas, the toroidal resolution is important as well as the radial resolution because the magnetic surfaces of LHD quickly change when the observation chord is tilted at a slightly different toroidal location. Horizontal dispersion is therefore selected for the present spectrometer. As a result, the toroidal resolution of 75 mm is achieved at the plasma position. An enough radial resolution of 10 mm is also obtained at spatial-resolution slit width of 0.2 mm. In order to measure the full radial profile of LHD plasmas the spectrometer is placed at a distance of {approx}9200 mm away from the plasma center and a backilluminated charge-coupled device with a size of 6.6x26.6 mm{sup 2} is set vertical to the horizontal dispersion. Half of the LHD plasma, i.e., {approx}50 cm, can be measured along the vertical direction at horizontally elongated plasma cross section. A full vertical profile can be obtained by changing the vertical angle of the EUV spectrometer. As an example the full vertical profile of edge C IV (312.4 A) emission is presented. A wavelength interval of 35-65 A can be simultaneously observed, which varies according to the wavelength to be measured. A local emission profile of Fe XX (132.67 A) is also presented after Abel inversion as a typical example of the core EUV emission. Finally, the EUV spectrometer is absolutely calibrated using EUV bremsstrahlung continuum profile in comparison with absolute values of visible bremsstrahlung continuum profile because the bremsstrahlung continuum can be easily detected in high-density discharges of LHD.},
doi = {10.1063/1.3299060},
url = {https://www.osti.gov/biblio/22053939}, journal = {Review of Scientific Instruments},
issn = {0034-6748},
number = 3,
volume = 81,
place = {United States},
year = {Mon Mar 15 00:00:00 EDT 2010},
month = {Mon Mar 15 00:00:00 EDT 2010}
}