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@ARTICLE{Dickheuer:864065,
      author       = {Dickheuer, Sven and Marchuk, Oleksandr and Ertmer, Stephan
                      and Goriaev, Andrei and Ialovega, Mykola and Göths, Beatrix
                      and Krasikov, Yury and Mertens, Philippe and Kreter, Arkadi},
      title        = {{I}n situ measurement of the spectral reflectance of
                      mirror-like metallic surfaces during plasma exposition},
      journal      = {Nuclear materials and energy},
      volume       = {17},
      issn         = {2352-1791},
      address      = {Amsterdam [u.a.]},
      publisher    = {Elsevier},
      reportid     = {FZJ-2019-03974},
      pages        = {302 - 306},
      year         = {2018},
      abstract     = {Visible spectroscopy in fusion plasmas crucially depends on
                      the optical properties of first mirrors withstanding a
                      considerable amount of radiation and particle fluxes. As a
                      result of this interaction the optical properties of the
                      mirrors could be changed so that a cleaning of the mirror is
                      regularly required. Thus the reflectance of the first mirror
                      must be monitored in situ. The newly developed
                      Doppler-Shifted Reflectance Measurement (DSRM) diagnostic
                      provides the spectral reflectance of mirrors in the absence
                      of any calibration sources. It is based on the emission of
                      fast H/D atoms in a low density Ar-H plasma by applying a
                      negative potential on the order of to the mirror surface.
                      Until now, the experimental data were restricted to measure
                      only the fast atoms emission at the Hα line. In this work
                      we prove that the new technique also provides the mirror
                      reflectance at the Hβ line (Cu) (486 nm) relevant for the
                      charge-exchange recombination spectroscopy (CXRS)
                      measurements of the He II line (468 nm) in ITER. Moreover,
                      the DSRM diagnostic remains sensitive to the polarization of
                      the reflected light of a W mirror. We present the first
                      experimental data on the time-dependent regime of operation:
                      in situ monitoring of the degradation of an Al mirror is
                      shown as a function of the mirror temperature. The passive
                      heating of the mirror was performed by the plasma itself,
                      which makes the separation between the impact of high
                      temperature and plasma erosion on the mirror reflectance for
                      the temperatures above 500 K impossible. A very good
                      agreement of the experimental and the theoretical data
                      calculated using the Drude theory for the temperature below
                      500 K is found. For the temperatures above 500 K the
                      degradation of the reflectance of the mirror is determined
                      by the erosion of Al, which is confirmed by monitoring the
                      Al I spectral lines in unison.},
      cin          = {IEK-4},
      ddc          = {624},
      cid          = {I:(DE-Juel1)IEK-4-20101013},
      pnm          = {174 - Plasma-Wall-Interaction (POF3-174)},
      pid          = {G:(DE-HGF)POF3-174},
      typ          = {PUB:(DE-HGF)16},
      UT           = {WOS:000454165000044},
      doi          = {10.1016/j.nme.2018.11.012},
      url          = {https://juser.fz-juelich.de/record/864065},
}