Development of Calibration-Free Laser-Induced-Breakdown-Spectroscopy based techniques for deposited layers diagnostics on ITER-like tiles

• LIBS system “in situ” and remote for new generation fusion machines
• Atomic composition of plasma facing component samples in fusion machines
• Calibration free method for a qualitative/quantitative analysis is discussed.
• Description of a new simplified calibration free method (partial calibration free)
• LIBS for screening erosion/redeposition during operation of fusion machines

High temperature plasma in hydrogen isotopes is peculiar of thermonuclear fusion devices. The study of plasma–wall interaction is of paramount importance for avoiding both damage of plasma facing components (PFCs) and pollution of the plasma. To assure continuous and fault-free operation a strict control must be exerted on the amount of impurities deposited on, and of the fuel retained in the PFCs. This requirement makes Laser-Induced-Breakdown-Spectroscopy (LIBS) an ideal candidate for on-line quantitative monitoring of the walls of the current as well as of the next generation fusion devices like the International Thermonuclear Experimental Reactor (ITER).An experimental setup has been designed and realized in order to optimize the characteristics of a LIBS system working at low pressure and remotely, and it has been utilized in combination with calibration free procedures for quantitative analysis. In this work, a partial calibration free method has been developed for single shot analysis of hydrogen isotopes retention at the PFCs-like surfaces, based on the acquisition of high resolution spectra in a narrow wavelength range. Results of calibration free and partial calibration free have been obtained on suitably deuterated samples; preliminary spectroscopic considerations on tritium detection are also presented.