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@ARTICLE{vanderMeiden:902608,
      author       = {van der Meiden, H. J. and Almaviva, S. and Butikova, J. and
                      Dwivedi, V. and Gasior, P. and Gromelski, W. and Hakola, A.
                      and Jiang, XI and Jõgi, I. and Karhunen, J. and Kubkowska,
                      M. and Laan, M. and Maddaluno, G. and Marín-Roldán, A. and
                      Paris, P. and Piip, K. and Pisarčík, M. and Sergienko, G.
                      and Veis, M. and Veis, P. and Brezinsek, S.},
      title        = {{M}onitoring of tritium and impurities in the first wall of
                      fusion devices using a {LIBS} based diagnostic},
      journal      = {Nuclear fusion},
      volume       = {61},
      number       = {12},
      issn         = {0029-5515},
      address      = {Vienna},
      publisher    = {IAEA},
      reportid     = {FZJ-2021-04403},
      pages        = {125001 -},
      year         = {2021},
      abstract     = {Laser-induced breakdown spectroscopy (LIBS) is one of the
                      most promising methods for quantitative in-situ
                      determination of fuel retention in plasma-facing components
                      (PFCs) of magnetically confined fusion devices like ITER and
                      JET. In this article, the current state of understanding in
                      LIBS development for fusion applications will be presented,
                      based on a complete review of existing results and
                      complemented with newly obtained data. The work has been
                      performed as part of a research programme, set up in the
                      EUROfusion Consortium, to address the main requirements for
                      ITER: (a) quantification of fuel from relevant surfaces with
                      high sensitivity, (b) the technical demonstration to perform
                      LIBS with a remote handling system and (c) accurate
                      detection of fuel at ambient pressures relevant for ITER.
                      For the first goal, the elemental composition of ITER-like
                      deposits and proxies to them, including deuterium (D) or
                      helium (He) containing W–Be, W, W–Al and Be–O–C
                      coatings, was successfully determined with a typical depth
                      resolution ranging from 50 up to 250 nm per laser pulse.
                      Deuterium was used as a substitute for tritium (T) and in
                      the LIBS experiments deuterium surface densities below 1016
                      D/cm2 could be measured with an accuracy of $∼30\%,$
                      confirming the required high sensitivity for fuel-retention
                      investigations. The performance of different LIBS
                      configurations was explored, comprising LIBS systems based
                      on single pulse (pulse durations: ps–ns) and double pulse
                      lasers with different pulse durations. For the second goal,
                      a remote handling application was demonstrated inside the
                      Frascati-Tokamak-Upgrade (FTU), where a compact, remotely
                      controlled LIBS system was mounted on a multipurpose
                      deployer providing an in-vessel retention monitor system.
                      During a shutdown phase, LIBS was performed at atmospheric
                      pressure, for measuring the composition and fuel content of
                      different area of the stainless-steel FTU first wall, and
                      the titanium zirconium molybdenum alloy tiles of the
                      toroidal limiter. These achievements underline the
                      capability of a LIBS-based retention monitor, which complies
                      with the requirements for JET and ITER operating in DT with
                      a beryllium wall and a tungsten divertor. Concerning the
                      capabilities of LIBS at pressure conditions relevant for
                      ITER, quantitative determination of the composition of PFC
                      materials at ambient pressures up to 100 mbar of N2, the D
                      content could be determined with an accuracy of $25\%,$
                      while for atmospheric pressure conditions, an accuracy of
                      about $50\%$ was found when using single-pulse lasers. To
                      improve the LIBS performance in atmospheric pressure
                      conditions, a novel approach is proposed for quantitative
                      determination of the retained T and the D/T ratio. This
                      scenario is based on measuring the LIBS plume emission at
                      two different time delays after each laser pulse. On virtue
                      of application of a double pulse LIBS system, for LIBS
                      application at N2 atmospheric pressure the
                      distinguishability of the spectra from H isotopes could be
                      significantly improved, but further systematic research is
                      required.},
      cin          = {IEK-4},
      ddc          = {620},
      cid          = {I:(DE-Juel1)IEK-4-20101013},
      pnm          = {134 - Plasma-Wand-Wechselwirkung (POF4-134)},
      pid          = {G:(DE-HGF)POF4-134},
      typ          = {PUB:(DE-HGF)16},
      UT           = {WOS:000718605000001},
      doi          = {10.1088/1741-4326/ac31d6},
      url          = {https://juser.fz-juelich.de/record/902608},
}