Hermann Joerg

We investigate the laser generated plasma in argon using Thomson scattering (TS) and optical emission spectroscopy (OES) techniques. The experiment is performed with two nanosecond Nd:YAG lasers. One generates the plasma while the second one probes the formed spark. The main objective of this work is to validate results of plasma diagnostics carried out with these two methods. Moreover, the existence of local thermodynamic equilibrium is studied by comparing the rates of the collisional to radiative processes (the McWhirter criterion), as well as relaxation times and diffusion lengths of argon neutrals and ions. Our results show satisfactory agreement between electron densities obtained with these two methods while we find very big discrepancy between electron temperature determined from the TS spectra and the excitation temperature from OES data.