Thesis (M.Sc.) - Cairo University - National Institute of Laser Enhanced Science - Department of Laser Application in Environmental Metrololgy Photochemistry and Agriculture

Laser induced breakdown spectroscopy (LIBS) is a well-known analytical technique that is used to determine the elemental composition of various solids, liquids and gases. LIBS analysis of metals at very low temperature is of great interest for industrial, biological and space exploration expeditions applications. In the present work, the effect of very low sample temperature on spectral emission intensity of laser-induced plasma as well as the plasma parameters under both atmospheric pressure and vacuum has been studied. For this purpose the sample has been cooled down to liquid nitrogen (LN) temperature 77K in a special vacuum chamber with a cold finger target holder in its center. Plasma has been produced on bronze alloy sample surface using fundamental wavelength of Nd:YAG laser. The optical emission from the plasma is collected by optical fiber and analyzed by an echelle spectrometer combined with an intensified CCD camera. The integrated intensities of different emission lines for different elements (Cu, Pb, Sn and Zn) have been calculated from the obtained LIBS spectra. Moreover, plasma parameters of bronze alloys (electron number density N and e plasma temperature T ) were investigated at both room and liquid e nitrogen temperatures under atmospheric pressure and vacuum conditions. The results suggest that reducing the sample temperature leads to decrease in the emission line intensities under both environments. Plasma parameters were found to decrease at atmospheric pressure but increased under vacuum conditions

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