Efficient discharge pumping of an XeCl laser using a high-voltage prepulse

Long, W. H.; Plummer, M. J.; Stappaerts, E. A.

doi:10.1063/1.94478

Cited by 132 publications

(23 citation statements)

References 7 publications

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“…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.…”

Section: Introductionmentioning

confidence: 99%

“…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.…”

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

1992

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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.

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Section: Introductionmentioning

confidence: 99%

mentioning

confidence: 99%

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

1992

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“…The efficiency of high-pressure, self-sustained, gas-discharge excited lasers, like excimers, can be improved by separating the electrical circuit in a high-impedance, high-voltage spiker circuit and a low impedance sustainer circuit which deposits the main part of the stored energy into the discharge [1]. The spiker circuit provides a fast rising voltage pulse to increase the electron density from its preionization value to its quasi steady state value.…”

Section: Pacs: 4255gpmentioning

confidence: 99%

“…To separate the two circuits from each other at least one low inductance switch is needed to prevent the spiker energy from flowing into the low impedance sustainer circuit. Use can be made of a rail-gap switch [1] or an array of switches like thyratrons [2]. Very promising is the application of fast saturable inductors enabling high repetition rate operation.…”

Section: Pacs: 4255gpmentioning

confidence: 99%

A new mode to excite a gas-discharge XeCl laser

Timmermans¹,

Goor

Witteman

1993

Appl. Phys. B

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Abstract.The charge mode is a new mode to excite a discharge XeC1 laser based on the dynamics of a spikersustainer circuit with a magnetic pulse compressor. The breakdown voltage is higher than in any other mode, due to a very fast rise time. The higher breakdown voltage provides a wider discharge and we found that more energy can be deposited before discharge instabilities terminate the optical output. PACS: 42.55.GpThe efficiency of high-pressure, self-sustained, gas-discharge excited lasers, like excimers, can be improved by separating the electrical circuit in a high-impedance, high-voltage spiker circuit and a low impedance sustainer circuit which deposits the main part of the stored energy into the discharge [1]. The spiker circuit provides a fast rising voltage pulse to increase the electron density from its preionization value to its quasi steady state value. Once the discharge has been excited, the sustainer circuit can deposit the stored energy efficiently into the discharge because impedance matching is achieved by charging a Pulse Forming Network (PFN) to twice the dc-breakdown voltage of the gas. To separate the two circuits from each other at least one low inductance switch is needed to prevent the spiker energy from flowing into the low impedance sustainer circuit. Use can be made of a rail-gap switch [1] or an array of switches like thyratrons [2]. Very promising is the application of fast saturable inductors enabling high repetition rate operation. Several circuits have been proposed in which low-loss, high-frequency ferrites are applied to operate the spiker-sustainer circuit in a variety of modes [3][4][5]. Also saturable inductors made of glassy alloys have been used, however, these appear to have higher losses [3].There is a number of reasons why the rise time of the spiker voltage should be as short as possible. Firstly, besides making an electron avalanche, the spiker circuit must also bring the saturable inductor into saturation when a magnetic switch is used. A short rise time lowers the amount of magnetic core material needed and therefore decreases the loss in the saturable inductor.Secondly, a short rise time increases the breakdown voltage of the gas and this provides longer stability. Dyer [6] showed for a TEA CO 2 laser, that small perturbations in the electrical field during the avalanche phase cause fluctuations in the electron density which in case of an excimer laser can initiate long term instabilities like the halogen depletion instability [7].Thirdly, a short rise time prevents preionisation electrons from drifting away from the cathode during the preavalanche phase, which can cause a region with insufficient overlap of the avalanche heads that leads to the onset of streamers [8].Finally, a high breakdown voltage ignites a larger part of the preionized volume as will be shown in this paper. The width of the discharge also depends on the curvature of the electrodes and on the spatial distribution of the preionization electron density.In this paper we describe the performance ...

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“…Spiker-sustainer circuits [5] comprise of two electrical circuits. A highimpedance, high-voltage spiker circuit and a low impedance sustainer circuit which deposits the main part of the stored energy into the discharge.…”

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Optimisation of the pulse duration of a discharge-pumped XeF(B?X) excimer laser

et al. 1995

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Abstract.In an x-ray preionised XeF(B~X) dischargeexcited laser driven by a magnetic-spiker sustainer circuit with a magnetic pulse compressor the influence of the various parameters on the optical pulse duration was experimentally investigated. Laser pulses at 2= 351 nm with a duration of 212 ns (FWHM) have been achieved in a NF3/Xe/Ne mixture by using very low (0.25 mbar) NF3 partial pressures in a total gas pressure of 2.5 bar and with a high-reflecting output coupling mirror. 42.55.Gp; 42.60.By; 52.80 In recent years long optical pulse discharge excited excimer lasers became of practical and scientific interest. The low peak power associated with long-pulse operation permits greater laser energy transfer through fused silica fibers, making these lasers attractive sources for medical applications. In addition, the increased number of cavity round-trips times provided by long-pulse operation permits the control of the laser divergence, line width, polarisation, and level of amplified spontaneous emission. There are a number of factors such as the electrical circuit, halogen concentration, total pressure, output coupling mirror transmission and electrical energy deposition which influence the rare-gas halide laserpulse duration. Recently, the use of magnetic-spiker sustainer excitation circuits for XeC1 rare-gas halide lasers has resulted in a higher efficiency, longer optical pulse durations and higher beam quality compared to conventional electrical discharge excitation circuits [1][2][3]. PACS:The magnetic-spiker sustainer technology also has been used to achieve long optical pulse KrF (170 ns) [1] and KrC1 (185 ns) [4] laser operation. Spiker-sustainer circuits [5] comprise of two electrical circuits. A highimpedance, high-voltage spiker circuit and a low impedance sustainer circuit which deposits the main part of

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Efficient discharge pumping of an XeCl laser using a high-voltage prepulse

Cited by 132 publications

References 7 publications

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

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

A new mode to excite a gas-discharge XeCl laser

Optimisation of the pulse duration of a discharge-pumped XeF(B?X) excimer laser

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