Short-pulse KrF amplifier using spatially tunable x-ray preionization.

S Szatmári

doi:10.1063/1.5143202

Abstract

The small saturation energy density of excimers requires amplifiers of large cross sections for amplification of short pulses of already medium power. Homogeneous excitation of large volumes of fluorine-based gas mixtures by discharge pumping is a critical interplay of the properties of both pumping and preionization, generally necessitating an intense spatially and temporally controlled x-ray preionization. In the present realization, the stringent intensity requirements of preionization are fulfilled by reducing the pulse duration of the x-ray flash to ∼16 ns and by positioning the x-ray source in the near vicinity of the active volume. It is proven both theoretically and experimentally that by proper choice of the positions of two cylindrical x-ray guns, the spatial distribution of preionization can be tuned to (and around) the optimum distribution. In this way, the spatial distribution of the discharge can also be controlled, giving a practical method to compensate for eventual inhomogenities of the E-field of excitation and to tune the discharge to the desired geometry. In this paper, design considerations and experimental realization of a KrF excimer amplifier of ∼5 × 4 cm2 cross section and a spatially tunable x-ray preionization are presented.

Highlights

In view of the recent progress of IR solid-state laser systems, high-brightness ultraviolet (UV) excimer lasers can be regarded as complementary sources
Three different x-ray tube positions were considered; arrangement I represents preionization of a single source from above
As a part of this activity, a short-pulse, twin, cylindrical x-ray gun is realized, which fulfills the needs of an efficient preionization of fluorine-based gas mixtures, with regard to its temporal, spatial, and intensity requirements

Summary

Introduction

In view of the recent progress of IR solid-state laser systems, high-brightness ultraviolet (UV) excimer lasers can be regarded as complementary sources. Their main advantage occurs in those experiments where high photon energy, optimum spatial concentration, and/or efficient conversion of the pulse energy to radiation of even shorter wavelength are needed.. The performance of short-pulse UV systems is definitely below that of the IR solidstate systems as the maximum peak power is concerned.3–6 This is primarily due to the difficulties associated with the construction of short-pulse UV amplifiers and with the inherently limited energy extraction from excimer amplifiers of short energy storage time..

Objectives

Results

Conclusion