•Clemens Walther¹ und Gerhard Geipel^2
1Forschungszentrum Karlsruhe, Institut für nukleare Entsorgung, Postfach 3640, 76021 Karlsruhe
²Institut für Radiochemie, Forschungszentrum Rossendorf e.V., Postfach 510119, 01314 Dresden

Laser induced breakdown spectroscopy is being used for particle detection in aqueous environments for more then ten years now [1]. While plasma creation in pure media is well understood, there are contradictory results in literature for description of the evolution of the plasma plume after ignition. Also the influence of particles for the plasma buildup is a subject to further investigations. In the present work the plasma is created by lasers of different pulse lengths (100 ps - 10 ns) and the optical emission is observed time resolved using a picosecond CCD camera. By means of a microscope lens the spatial expansion is measured and with a Czerny Turner spectrometer spectral resolution is achieved. In addition transmission and extinction of a weak second laserpulse through the plasma is measured at different times of the plasma evolution. Hence temperature and electron density of the plasma can be estimated.