Recombination XUV Lasers Driven by Low Energy Picosecond Pulses from a High Brightness KrF Raman Laser

Abstract

There is great interest in the development of XUV lasers with driver energies of a few joules rather than a few kilojoules. One of the most promising ways to accomplish this is based upon the use of fast adiabatic cooling to produce population inversion in recombination to hydrogenic ions(l). Theoretical modelling(2) indicates that the optimum driver for this scheme should produce pulses of duration < 10 ps, ultraviolet wavelength and focusability to sub 10 µm line foci with length of the order 1 cm. Under these conditions saturated laser action at wavelengths below 20 nm is predicted in plasmas created from fibre targets of < 10 µm radius with driver energy < 10 J (see eg Fig 1). Preliminary experimental studies have been carried out using a high brightness 5 J, 10 ps KrF pumped Raman laser beam(3) with observations of fluorescence and possible amplification on the Balmer-α transitions of C VI, O VIII(4). In a current experiment these phenomena are being studied in detail. Our paper will review the theoretical basis for the X-ray laser scheme, describe the experimental and diagnostic system, review previous preliminary results and report on the results of the current more detailed experiment.