<title>Gas lifetime restriction in ArF and KrF avalanche discharge lasers</title>

The results of gas lifetime experiments in ArF and KrF avalanche discharge lasers utilizing different laser chamber materials are presented. Utilization of aluminum ceramics protecting laser chamber polymeric walls from UV gas discharge radiation give us the possibility to increase significantly gas lifetime. Two different physical mechanisms restricting gas lifetime were considered. The first one is connected with interaction between fluoride and organic molecules. The second one (unremovable in avalanche discharge lasers) is connected with electrode erosion processes. The numerical evaluations of the gas lifetime limitation value in ArF and KrF lasers are presented. The different ways of further increasing gas lifetime are discussed.