Analysis of deposited layers on plasma facing components by laser-induced breakdown spectroscopy: Towards ITER tritium inventory diagnostics

Because of the necessity of tritium inventory diagnostics in the framework of ITER, laser-induced breakdown spectroscopy (LIBS) is under development to analyse the deposited layers on plasma facing components. By means of a fast imaging technique, the time evolutions of the plume intensity and size are investigated. Time- and space-resolved optical emission spectroscopy is applied to characterize the expansion dynamics of ionized and neutral species within the ablation plume. A parametric study (laser fluence and pulse duration, gas pressure) is performed to determine the optimized operational conditions for LIBS analyses with samples from the Tore Supra reactor. To overcome the difficulties of quantitative LIBS measurements, an analysis procedure based on the calculation of the spectral radiance of the plasma in local thermodynamic equilibrium is applied.