Effective laser-induced removal of co-deposited layers from plasma-facing components in a tokamak

Abstract

An experimental set-up and spectroscopy diagnostic method for laser-induced fuel removal and decomposition of co-deposited layers on plasma-facing components from tokamaks are described. For irradiation of a graphite limiter tile from the TEXTOR tokamak Nd:YAG 3.5-ns pulse laser with a repetition rate of 10 Hz and single pulse energy of up to 0,8 J at 1,06 µm has been used. The spectroscopy system allowed recording of spectra in the visible wavelength range including CII and Dα spectral lines . The evolution of CII and Dα spectral lines was observed pulse-by-pulse during the co-deposit removal. The efficient ablation of the 45 µm thick co-deposit occured after approximately 50 laser pulses.

In situ and remote laser diagnostics for material characterization from plasma facing components to Cultural Heritage surfaces

“…The LIBS technique was previously used for the post-mortem investigation of elements of plasmafacing components from tokamaks [11] or fusion relevant mixed material samples [12,13].…”

One-point calibration laser-induced breakdown spectroscopy for the quantitative analysis of EAST-like plasma-facing materials

“…In 2006, the co-deposited layer characterization and removal control by optical spectroscopy coupled to laser ablation were implemented in the laboratory. 4,5 By recording the spectral emission lines of laser-induced plasma shot by shot, it is possible to follow in the real-time co-deposited layer removal and to evaluate the co-deposited layer thickness. Laser-induced breakdown spectrometry (LIBS) was explored as a potential candidate to in situ monitor the layer composition and fuel retention on tokamak devices such as TEXTOR, EAST, FTU and other various laboratory experiments.…”

Preliminary results ofin situlaser-induced breakdown spectroscopy for the first wall diagnostics on EAST

“…A number of investigations have been conducted on LIBS in the laboratory for impurity deposition composition and fuel retention in deposition layer analysis toward ITER application [8,9]. In 2011, Huber et al studied the feasibility of applying LIBS for in situ characterization of deposited layers in TEXTOR [10].…”