Effective laser–induced removal of co–deposited layers from plasma–facing components in a tokamak P. Gasior, A. Czarnecka, P. Parys, M. Rosinski, J. Wolowski Institute of Plasma Physics and Laser Microfusion, Association EURATOM, 01–497 Warsaw, Poland e-mail: gasior@ifpilm.waw.pl J. Hoffman, Z. Szymanski Institute of Fundamental Technological Research, Swietokrzyska St. 21, 00–049 Warsaw Poland V. Philipps Institute of Plasma Physics, Forschungszentrum J¨ ulich, Association EURATOM – FZJ, D–52425 J¨ ulich, Germany M. Rubel Alfv´ en Laboratory, KTH, Royal Institute of Technology, Association EURATOM – VR, SE–100 44 Stockholm, Sweden Received 28 April 2006 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 . The evolution of CII and Dα spectral lines was observed pulse–by–pulse during the co–deposite removal. The efficient ablation of the 45 μm thick co–deposit occured after approximately 50 laser pulses. PACS : 52.38.-r, 52.38.Mf, 52.70.Nc, 81.05.Uw, 82.50.Bc, 52.40.Hf, 07.60.Rd 42.62.Fi Key words : tokamaks, laser ablation, spectroscopy, co–deposit removal 1 Introduction The carbon based materials, in particular CFC, due to good thermo–mechanical properties is planed to be used for the lower vertical target, i.e. for the strike point zone in ITER [1]. The main drawback of such a solution is that the presence of this element can lead to the fuel accumulation by co–deposition [2–5]. Massive fuel accumulation at the level which was observed in remote areas shadowed from the direct plasma impact at JET [6–8] would have a serious impact on the safety and economy of the ITER operation. Based on the experience gathered following the full deuterium–tritium campaigns in carbon–wall devices, e.g. TFTR [9] and JET [10], a development of reliable and efficient methods of fuel removal is indispensable. Czechoslovak Journal of Physics, Vol. 56 (2006), Suppl. D D1