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

Journal Article · Tue Nov 15 00:00:00 EST 2011 · Review of Scientific Instruments

DOI:https://doi.org/10.1063/1.3658050· OSTI ID:22066279

Chunfeng, Dong; Erhui, Wang ^[1]; Morita, Shigeru; Goto, Motoshi ^[1]

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1. Department of Fusion Science, Graduate University for Advanced Studies, Toki 509-5292, Gifu (Japan)

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 with 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.

• OSTI ID: 22066279
• Journal Information: Review of Scientific Instruments, Vol. 82, Issue 11; Other Information: (c) 2011 American Institute of Physics; Country of input: International Atomic Energy Agency (IAEA); ISSN 0034-6748
• Country of Publication: United States
• Language: English

Related Subjects

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