skip to main content

Title: Absolute intensity calibration of flat-field space-resolved extreme ultraviolet spectrometer using radial profiles of visible and extreme ultraviolet bremsstrahlung continuum emitted from high-density plasmas in Large Helical Device

A precise absolute intensity calibration of a flat-field space-resolved extreme ultraviolet (EUV) spectrometer working in wavelength range of 60-400 A is carried out using a new calibration technique based on radial profile measurement of the bremsstrahlung continuum in Large Helical Device. A peaked vertical profile of the EUV bremsstrahlung continuum has been successfully observed in high-density plasmas (n{sub e}{>=} 10{sup 14} cm{sup -3}) with hydrogen ice pellet injection. The absolute calibration can be done by comparing the EUV bremsstrahlung profile with the visible bremsstrahlung profile of which the absolute value has been already calibrated using a standard lamp. The line-integrated profile of measured visible bremsstrahlung continuum is firstly converted into the local emissivity profile by considering a magnetic surface distortion due to the plasma pressure, and the local emissivity profile of EUV bremsstrahlung is secondly calculated by taking into account the electron temperature profile and free-free gaunt factor. The line-integrated profile of the EUV bremsstrahlung continuum is finally calculated from the local emissivity profile in order to compare with measured EUV bremsstrahlung profile. The absolute intensity calibration can be done by comparing measured and calculated EUV bremsstrahlung profiles. The calibration factor is thus obtained as a function of wavelength withmore » excellent accuracy. It is also found in the profile analysis that the grating reflectivity of EUV emissions is constant along the direction perpendicular to the wavelength dispersion. Uncertainties on the calibration factor determined with the present method are discussed including charge-coupled device operation modes.« less
Authors:
;  [1] ; ;  [1] ;  [2]
  1. Department of Fusion Science, Graduate University for Advanced Studies, Toki 509-5292, Gifu (Japan)
  2. (Japan)
Publication Date:
OSTI Identifier:
22066279
Resource Type:
Journal Article
Resource Relation:
Journal Name: Review of Scientific Instruments; Journal Volume: 82; Journal Issue: 11; Other Information: (c) 2011 American Institute of Physics; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
70 PLASMA PHYSICS AND FUSION TECHNOLOGY; ACCURACY; BREMSSTRAHLUNG; CALIBRATION; CHARGE-COUPLED DEVICES; ELECTRON TEMPERATURE; EMISSIVITY; EXTREME ULTRAVIOLET RADIATION; HYDROGEN; ICE; LHD DEVICE; LIGHT BULBS; MAGNETIC SURFACES; PELLET INJECTION; PLASMA DENSITY; PLASMA PRESSURE; REFLECTIVITY; ULTRAVIOLET SPECTROMETERS; WAVELENGTHS