B. Fontaine

HIGH REPETITION RATE SPIKER-SUSTAINER XECL LASER

An X-ray preionized spiker-sustainer XeCl-excimer laser operating at high repetition frequency (1000 Hz) and 220 W of average laser power is demonstrated. The pulse energy and the pulse duration (160 ns) are virtually independent of the repetition frequency. Comparison with aC-L-C circuit shows superior properties of spiker-sustainer excitation for high-frequency operation. Furthermore, a variation of the overshoot mode is proposed.

High-Pulse Repetition Rate Limitations in a High Average Power XeCl Laser

Potential applications of high average power ultraviolet lasers are numerous in fields as different as semiconductor processing, photochemistry, long-range communications, laser-matter interactions… These applications stimulate a large amount of studies in U.S.A, U.S.S.R. and Europe(1),(2),(3),(4),(5).The scaling of ultraviolet and visible lasers to high output pulse energy and high pulse repetition frequency (prf) to achieve average powers in the range of 0.1 to 1 kW is under investigation at l’Institut de Mecanique des Fluides de Marseille in a closed cycle loop to conserve the expansive gas mixture typical of excimer lasers.

Kr2+Cs: a new class of triatomic excimer molecules

Alkali rare gas triatomic ionic excimers have been observed for the first time. These molecules have been produced by electron beam excitation of rare gas alkali mixtures at high pressure and high temperature. Emission spectra centered at approximately 159 nm have been observed and attributed to Kr2+Cs ions. Lifetimes and binding energies of the lowest excited states have been estimated. Simple kinetic considerations allowed us to propose two formation processes of these ions and to estimate their rate constant.

Influence of electrode roughness on the discharge quality of a high-PRF long-pulse XeCl laser

The uniformity and stability of discharge process in a high pulse repetition frequency (PRF) long pulse XeCl laser are investigated for three different copper electrode roughnesses versus PRF (f less than or equal to 500 Hz; 10 shots). The discharge quality evolution is experimentally analyzed from discharge photographs obtained with a CCD video camera and pressure perturbation measurements achieved with a piezoelectric pressure probe placed very close to the discharge volume.

Parametric study of small-volume long-pulse x-ray preionized XeCl laser with double-discharge and fast magnetic switch

An experimental parametric study of a small volume x-ray preionized XeCl laser which uses the double discharge (spiker-sustainer) principle and a new fast ferrite magnetic switch is presented. This high-efficiency discharge excitation system, with a Ne/Xe/HCI mixture at relatively low pressure (P equals 2.5 atm.), in a 50 cm3 active volume (25(DOT)2(DOT)1 cm3), has made possible an efficiency of 3.2% in energy and 4% in power at maximum with up to 140 mJ of extracted optical energy in a 130 ns (FWHM) laser pulse in switch mode. The authors discuss laser characteristics dependence with magnetic switch and electrical circuit parameters, for switch mode. Future studies of the present advanced excitation system for conditions of very high PRF, in the frame of Eureka EU205 Eurolaser program, are presented. The experimental part of these planned studies will be made with LUX very high PRF high average power IMFM test-bed

Modeling of a long-pulse high-efficiency XeCl laser with double discharge and fast magnetic switch

A complete model of a long-pulse x-ray preionized self-sustained discharge XeCl excimer laser has been established for the case of excitation by an advanced electrical circuit associating a double discharge (spiker/sustainer) and a fast low-loss ferrite magnetic switch with pulsed reset. This model allows simulation of the potential working conditions of the IMFM high average power, very high repetition rate LUX test-bed. The model, which considers Ne as buffer gas and HCl as halogen donor, includes a rate equation for species with the most recent available rate constant values, circuit equations with time-dependent ferrite inductance and plasma impedance and rate equation for laser emission taking into account absorbtions. Modeling takes into account time delay between spiker and sustainer, low value of sustainer field and dynamics of magnetic switch. The model has been validated with a long- pulse x-ray preionized XeCl laser, with double discharge and magnetic switching, developed at IMFM, which has already obtained over 3% efficiency and 140 mJ extracted energy in 150 ns (FWHM) from a 50 cm3 active volume at 2.5 atm. pressure. Numerical results are in good agreement (within 30%) with IMFM experimental results. A parametric study of the XeCl laser with double discharge and fast magnetic switch is presented as well as a comparison with both experiments and numerical results of excitation by a C-L-C classical circuit for the same geometric and gas conditions and the same input energy.© (1991) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Fast-flow gas-dynamic effects in high-pulse repetition-rate excimer lasers

The use of a high pulse repetition rate in a high average power excimer laser radicalizes the role of acoustic and aerodynamic phenomena. Accounts are presently given of the current understanding of interferometric wave analysis results, the damping of acoustic or shock waves, and the correlation between pressure perturbation level and energy in laser pulses

Kinetics and electrical modeling of a long-pulse high-efficiency XeCl laser with double discharge and fast magnetic switch

A complete model of the long pulse XeCI excimer laser excited by a double discharge with fast magnetic switch has been established for an Ne/Xe/HCI active medium. This model simulate one of the potential working conditions of the IMFM high average power LUX test-bed. Model includes rate equations for species with most recent availiable rate constant values, circuit equations with time dependant ferite switch inductance and plasma impedance and rate equation for laser emission taking into account absorptions. The model allows to simulate very long laser pulses (150-200 ns) and numerical results are in good agreement (within 30 %) with experimental results obtained at IMFM.

Modelling of the X-Ray Preionised XeCl Self-Sustained Discharge Laser

A complete model of the long pulse X-ray preionised self-sustained discharge XeCl laser has been established for transfer capacitor and PFN circuits and Ne/Xe/HCl active medium. This model simulates the I.M.F.M. high average power Lux laser test-bed. The model includes rate equations for species with most recent rate constant values, rate equation for laser emission taking into account absorptions, and circuit equations with time dependant plasma impedance. The model shows the dominant effects of electron quenching and Xe2Cl absorption on laser output and efficiency. Results of the model are in good agreement (within 30%) with experimental results obtained with LUX device.

Performance Characteristics Of A Long Pulse And High Average Power Xec1 Discharge Laser

Performance of an advanced XeC1 discharge pumped laser (X=308 nm) using a wire ion plasma X-Ray gun (W.I.P.) for preionisation is presented. This excimer laser optimized both for long use (100 ns), high prf (1 KHz), high average power (200 Watts) and high efficiency is described in details as well as spatial and temporal characteristics of the UV laser beam.