D. A. Whelan

Demonstration of X-ray Holography with an X-ray Laser

An x-ray hologram was made by means of an x-ray laser and a laser-quality near normal incidence x-ray mirror. The high brightness and large coherence lengths of x-ray lasers now offer the potential for in vitro three-dimensional high-resolution holographic images of dynamically varying biological microstructures.

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

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 AA 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 AA 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.

Soft-x-ray amplification at 50.3 Å in nickellike ytterbium

Nickellike ions of ytterbium (Yb42+) have been produced in long exploding foil plasmas. The plasmas were formed by short-pulse laser irradiation of thin foils of ytterbium with line-focused high-intensity 0.53-μm light. Soft-x-ray line emissions at 50.26 and 56.09 A are identified as 4d–4p, J = 0−1 transitions in the nickellike ionization stage of ytterbium. The energy emitted in the line at 50.26 A along the axis of the plasma is observed to increase nonlinearly with plasma length, consistent with a small-signal gain of 1.2 ± 0.4 cm−1.

Lawrence Livermore National Laboratory X-Ray Laser Research: Recent Results

Since the successful demonstration of gain in neon-like selenium using an exploding foil amplifier, the x-ray laser group at Lawrence Livermore National Laboratory has investigated further the exploding foil amplifier concept for use in XUV lasers. Results are reported of the characteristics of selenium amplifiers up to 50 mm in length. Observation of at least 16 gain lengths for the 206 Å line of selenium is reported. Output powers in excess of 1 MW have been measured in pulses of approximately 200 picoseconds. The effects of refraction on the performance of long amplifiers have been studied. The occurrence time of the x-ray laser output relative to the input heating pulse has been measured and found to be in disagreement with a recent model that suggests three-body recombination driven by rapid radiative cooling as the inversion process in the selenium plasma.

No pain—no gain: The complex art of soft x‐ray laser target design and analysis

We review our methodologies in the design and analysis of soft x‐ray laser experiments. We convolve large scale 2‐D hydro code output with detailed atomic data bases in a kinetics code with 1‐D or 2‐D line transfer. The time and space dependent level population data is then post processed further with a beam transport code, including refraction, to predict actual experimental results. While mysteries do remain, we present many examples that show how this complex modeling procedure is crucial in explaining experimental results.