Soft X-ray laser source development and applications experiments at Lawrence Livermore National Laboratory

Abstract

Recent progress in experimental laboratory soft x-ray laser research at Lawrence Livermore National Laboratory (LLNL) is reviewed. Research at LLNL in this area has concentrated on further characterising and understanding neon-like x-ray laser plasmas, investigating soft x-ray amplification at shorter wavelengths, and demonstrating examples of x-ray laser applications. For the standard 200 8, neon-like selenium collisional excitation laser, the output source size as well as the beam time history, divergence, energy and spatial profile have been measured. Gain has been,demonstrated at wavelengths as short as 50.3 8, in nickel-like ytterbium. Several recombination x-ray laser schemes have also been investigated. X-ray laser holography, cavity operation of an x-ray laser, and the capability to point and focus the output laser beam have been demonstrated.

ELECTRON–ION COLLISIONAL IONIZATION CROSS SECTIONS AND RATES FOR THE Ne ISOELECTRONIC SEQUENCE

“…Electron impact ionization cross sections, as well as collision strengths, are important data in modeling the structure and dynamics of high-temperature plasmas occurring both naturally in space and artificially in fusion devices [1,2]. In recent years, the study of soft x-ray lasers, especially for Li-like ions and Ne-like ions, has made rapid progress [3][4][5][6]. Electron impact ionization cross sections and rates for highly charged ions are very important atomic parameters for the above studies.…”

Development of small scale soft x-ray lasers

“…However in view of the above results it is clear that while this may be an encouraging sign of gain it is by no means sufficient proof that gain is present. As was done in some earlier works (for example Matthews 1985, Jamelot 1988, Keane 1989, and Kim 1989a, it is critical to monitor the emission from nearby spontaneous emission lines in the same ion, preferably lines with the same lower level as the lasing line, to be assured that one is viewing a homogeneous plasma and that the comparison of plasmas of differing lengths is a valid. Checking that the spontaneous emission lines have a linear length dependence is particularly important fcr measurements of low gain-lengths, GL < 4, where the output intensities are not so different to spontaneous emission levels.…”

High ionization states observed in soft x-ray spectra from plasmas of second row transition elements produced by femtosecond laser pulses

“…Laser-produced plasmas (LPPs) formed by high intensity laser pulse irradiation of solid targets are good emitters of extreme ultraviolet (XUV) and soft x-ray (SXR) emission arising from discrete transitions, radiative recombination and bremsstrahlung. Such radiation sources have found use in various applications such as inertial-confinement fusion studies [2], x-ray laser development [3], water window sources [4,5], emission and absorption spectroscopy [6,7] and applications requiring XUV radiation of particular wavelengths and/or intensity [8,9]. While XUV and SXR emission from plasmas generated by nanosecond and picosecond lasers have been studied extensively (e.g.…”