Plasma and Fusion Research

Volume 7, 2402139 (2012)

Regular Articles

Extension of Wavelength Range in Absolute Intensity Calibration of Space-Resolved EUV Spectrometer for LHD Diagnostics
Chunfeng DONG1), Shigeru MORITA1,2), Motoshi GOTO1,2) and Erhui WANG2)
1)
National Institute for Fusion Science, Toki, Gifu 509-5292, Japan
2)
Department of Fusion Science, Graduate University for Advanced Studies, Toki, Gifu 509-5292, Japan
(Received 9 December 2011 / Accepted 25 June 2012 / Published 15 October 2012)

Abstract

A space-resolved extreme ultraviolet (EUV) spectrometer has been upgraded by extending the wavelength range to 30-650Å to explore impurity line emissions existing at shorter and longer wavelength sides. The absolute intensity calibration is implemented for measurement in the extended wavelength based on bremsstrahlung profiles simultaneously measured in EUV and visible ranges. For the purpose a wider entrance slit of 200 µm and a wider space-resolved slit of 1.0 mm are adopted to increase the number of photons to the spectrometer. As a result, the bremsstrahlung intensity can be enhanced by order of magnitude. A centrally peaked high-density discharge at ne(0) ≥ 1014 cm−3 is also used for the accurate calibration. Thus, the calibration becomes possible, even in longer wavelength side at λ ≥ 400 Å. The result at shorter wavelength range of 30-90Å shows a flat calibration factor, suggesting sudden changes of holographic grating efficiency and CCD detection efficiency, while the result at longer wavelength side of λ ≥ 400 Å shows a simple extension of the previous calibration factor.

Keywords

EUV bremsstrahlung, grating efficiency, absolute intensity calibration

DOI: 10.1585/pfr.7.2402139

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References

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This paper may be cited as follows:

Chunfeng DONG, Shigeru MORITA, Motoshi GOTO and Erhui WANG, Plasma Fusion Res. 7, 2402139 (2012).