<title>Effect of acoustic dampers on the excimer laser flow</title>

Abstract

It is well-known that to obtain a good quality laser beam in high repetitive rate excimer lasers, the acoustic waves due to a non uniform energy deposition between the electrodes, must be strongly damped. The unsteady two dimensional flow in eximer laser cavity has been described previously 1 by a numerical approach. The aim of this paper is to include in the numerical code a modelization of the sidewall mufflers in order to study the influence of the porous material on the behaviour of transverse and longitudinal waves in the excimer laser cavity. In the muffler, the flow is assumed one dimensional (y direction) and is coupled to the laser cavity flow. These flows are described by Euler equations and the numerical method is based on an explicit difference scheme assiociated with a corrected transport algorithm (Shasta method)2. The results show the propagation and the damping of longitudinal shock-waves and acoustic waves for different kind of mufflers. Different shapes of laser cavity are also investigated to study the influence of the electrode raduis curvature on the transverse waves. These results are compared to experimental results obtained from the L.U.X. laser of Institut de Mecanique des Fluides de Marseille.