DENSITIES AND LIFE TIME OF ELECTRONS IN KRF-ASTERISK LASER GAS-MIXTURES DURING THE X-RAY PREIONIZATION

The homogeneity and stability of TEA-Excimer laser discharges strongly depend on the preionization. A homogeneous discharge can only develop e if it is ensured that the electron density exceeds a certain level a t the moment of the ignition. The kinetic of these electrons during th e preionization is analyzed theoretically by the use of the Boltzmann equation for x-ray preionized KrF laser systems. The time dependent v elocity distribution of the electrons is calculated for different buff er gases and gas mixtures. The resulting electron densities and life t imes are discussed and compared with experimental investigations. It i s quantitatively shown at the first time that the kind of the buffer g as has a decisive influence on the velocity distribution, density and life time of the preionization electrons.