title: A fast-time-response extreme ultraviolet spectrometer for measurement of impurity line emissions in the Experimental Advanced Superconducting Tokamak.
abstract: A flat-field extreme ultraviolet (EUV) spectrometer working in the 20-500 Å wavelength range with fast time response has been newly developed to measure line emissions from highly ionized tungsten in the Experimental Advanced Superconducting Tokamak (EAST) with a tungsten divertor, while the monitoring of light and medium impurities is also an aim in the present development. A flat-field focal plane for spectral image detection is made by a laminar-type varied-line-spacing concave holographic grating with an angle of incidence of 87°. A back-illuminated charge-coupled device (CCD) with a total size of 26.6 × 6.6 mm(2) and pixel numbers of 1024 × 255 (26 × 26 μm(2)/pixel) is used for recording the focal image of spectral lines. An excellent spectral resolution of Δλ0 = 3-4 pixels, where Δλ0 is defined as full width at the foot position of a spectral line, is obtained at the 80-400 Å wavelength range after careful adjustment of the grating and CCD positions. The high signal readout rate of the CCD can improve the temporal resolution of time-resolved spectra when the CCD is operated in the full vertical binning mode. It is usually operated at 5 ms per frame. If the vertical size of the CCD is reduced with a narrow slit, the time response becomes faster. The high-time response in the spectral measurement therefore makes possible a variety of spectroscopic studies, e.g., impurity behavior in long pulse discharges with edge-localized mode bursts. An absolute intensity calibration of the EUV spectrometer is also carried out with a technique using the EUV bremsstrahlung continuum at 20-150 Å for quantitative data analysis. Thus, the high-time resolution tungsten spectra have been successfully observed with good spectral resolution using the present EUV spectrometer system. Typical tungsten spectra in the EUV wavelength range observed from EAST discharges are presented with absolute intensity and spectral identification.
authors.affiliation: Institute of Plasma Physics Chinese Academy of Sciences, Hefei 230026, Anhui, China.
authors.forename: Ling
authors.initials: L
authors.lastname: Zhang
authors.affiliation: National Institute for Fusion Science, Toki 509-5292, Gifu, Japan.
authors.forename: Shigeru
authors.initials: S
authors.lastname: Morita
authors.affiliation: Institute of Plasma Physics Chinese Academy of Sciences, Hefei 230026, Anhui, China.
authors.forename: Zong
authors.initials: Z
authors.lastname: Xu
authors.affiliation: Institute of Plasma Physics Chinese Academy of Sciences, Hefei 230026, Anhui, China.
authors.forename: Zhenwei
authors.initials: Z
authors.lastname: Wu
authors.affiliation: Institute of Plasma Physics Chinese Academy of Sciences, Hefei 230026, Anhui, China.
authors.forename: Pengfei
authors.initials: P
authors.lastname: Zhang
authors.affiliation: Institute of Plasma Physics Chinese Academy of Sciences, Hefei 230026, Anhui, China.
authors.forename: Chengrui
authors.initials: C
authors.lastname: Wu
authors.affiliation: Institute of Plasma Physics Chinese Academy of Sciences, Hefei 230026, Anhui, China.
authors.forename: Wei
authors.initials: W
authors.lastname: Gao
authors.affiliation: National Institute for Fusion Science, Toki 509-5292, Gifu, Japan.
authors.forename: Tetsutarou
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authors.lastname: Ohishi
authors.affiliation: National Institute for Fusion Science, Toki 509-5292, Gifu, Japan.
authors.forename: Motoshi
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authors.affiliation: Institute of Plasma Physics Chinese Academy of Sciences, Hefei 230026, Anhui, China.
authors.forename: Junsong
authors.initials: J
authors.lastname: Shen
authors.affiliation: Institute of Plasma Physics Chinese Academy of Sciences, Hefei 230026, Anhui, China.
authors.forename: Yingjie
authors.initials: Y
authors.lastname: Chen
authors.affiliation: Institute of Plasma Physics Chinese Academy of Sciences, Hefei 230026, Anhui, China.
authors.forename: Xiang
authors.initials: X
authors.lastname: Liu
authors.affiliation: Institute of Plasma Physics Chinese Academy of Sciences, Hefei 230026, Anhui, China.
authors.forename: Yumin
authors.initials: Y
authors.lastname: Wang
authors.affiliation: Southwestern Institute of Physics, Chengdu 610041, Sichuan, China.
authors.forename: Chunfeng
authors.initials: C
authors.lastname: Dong
authors.affiliation: Department of Fusion Science, Graduate University for Advanced Studies, Toki 509-5292, Gifu, Japan.
authors.forename: Hongmin
authors.initials: H
authors.lastname: Zhang
authors.affiliation: Department of Fusion Science, Graduate University for Advanced Studies, Toki 509-5292, Gifu, Japan.
authors.forename: Xianli
authors.initials: X
authors.lastname: Huang
authors.affiliation: Institute of Plasma Physics Chinese Academy of Sciences, Hefei 230026, Anhui, China.
authors.forename: Xianzu
authors.initials: X
authors.lastname: Gong
authors.affiliation: Institute of Plasma Physics Chinese Academy of Sciences, Hefei 230026, Anhui, China.
authors.forename: Liqun
authors.initials: L
authors.lastname: Hu
authors.affiliation: Institute of Plasma Physics Chinese Academy of Sciences, Hefei 230026, Anhui, China.
authors.forename: Junlin
authors.initials: J
authors.lastname: Chen
authors.affiliation: Institute of Plasma Physics Chinese Academy of Sciences, Hefei 230026, Anhui, China.
authors.forename: Xiaodong
authors.initials: X
authors.lastname: Zhang
authors.affiliation: Institute of Plasma Physics Chinese Academy of Sciences, Hefei 230026, Anhui, China.
authors.forename: Baonian
authors.initials: B
authors.lastname: Wan
authors.affiliation: Institute of Plasma Physics Chinese Academy of Sciences, Hefei 230026, Anhui, China.
authors.forename: Jiangang
authors.initials: J
authors.lastname: Li