Simulation studies of the prepulse-main-pulse XeCl discharge lasers with magnetic switching

Abstract

Abstract.A self-consistent model of a self-sustained discharge XeC1 laser (Ne/Xe/HCI mixture) with prepulse-mainpulse excitation and magnetic switching which leads to high efficiency operation is described. The validity of the model is confirmed by comparing the results of the calculations with the measured time dependences of discharge voltage, current and lasing pulse for different operation modes as well as by comparing the results with the dependences of the laser output energy and efficiency on the charging voltage and capacitance of the pulse forming network for two different laser heads. The numerical evaluation has shown that our developed laser system operates under optimum conditions. PACS: 42.55.Gp Potential applications of excimer lasers as sources of UV radiation in industries, especially in photochemistry and materials processing require very high average power lasers. Commercially available excimer lasers produce hundreds of watts of average power at an efficiency of up to 2.5% in some cases 3% (e.g., LPX240i or LAMBDA4000). A number of laboratories are working on the development of excimer lasers with 1 kW average power by means of a fast flowing gas circulation system. A breakthrough in this development was obtained by the introduction of the so-called prepulse-main-pulse technique in which the prepulse is used for the avalanche ionization process during the breakdown phase whereas the main pulse is applied under quasi-steady-state conditions [1][2][3][4]. The introduction of passive magnetic switches for isolation of low-impedance sustainer and high-impedance spiker circuits instead of railgap switches enables long-life operation capability of the laser at high repetition rates [2][3][4] Computer modeling is a useful tool for investigating the physical processes occurring in the active media of excimer lasers and the influence of the large number of parameters that are involved. It supplements the experiments and will be used to optimize the development of various laser designs.In this paper we present a theoretical model of a high efficient discharge XeC1 laser with prepulse-main-pulse and the magnetic switching technique. The results of the computer simulations are compared with the experimental ones of the lasers developed at the Twente University of Technology [4]. The model is based on the standard excitation schemes of He [6] and Ne [7] based mixtures, which are in good agreement with the experimental data, including time dependences of the densities of discharge species. Although computer simulations were mentioned in [1,3] and shortly described in [8] (not including the Boltzmann equation for the electron distribution), we shall describe the complete model of a discharge XeC1 laser with the advanced excitation circuit and improved kinetics. We shall discuss and compare the results of the simulations with the experiments for different modes of laser operation and for different laser heads.

Experimental verification of a zero-dimensional model of the ionization kinetics of XeCl discharges

“…In agreement with [12,76] and in contrast to [9,77], our investigations show that NeXe + (as well as Xe +) is of minor importance in discharges containing HCl. In HCl-free discharges the ionization is balanced by electron recombination with these molecular ions.…”

Excimer Lasers – The powerful light source in the UV and VUV

“…For the most important formation channel at least one Xe + is needed to create a XeCl* molecule. The formation of XeCl* is described in the following reaction equations [3]: …”