We present the results of a benchmark experiment aimed at validating recent calculation techniques for the emission properties of medium and high-Z multicharged ions in hot plasmas. We use space- and time-resolved M-shell x-ray spectroscopy of a laser-produced gas jet xenon plasma as a primary diagnostic of the ionization balance dynamics. We perform measurements of the electron temperature, electron density, and average charge state by recording simultaneous spectra of ion acoustic and electron plasma wave Thomson scattering. A comparison of the experimental x-ray spectra with calculations performed ab initio with a non-local-thermodynamic-equilibrium collisional-radiative model based on the superconfiguration formalism, using the measured plasma parameters, is presented and discussed.

We have used point-projection K-shell absorption spectroscopy to infer the ionization and recombination dynamics of transient aluminum plasmas. Two femtosecond beams of the 100 TW laser at the LULI facility were used to produce an aluminum plasma on a thin aluminum foil (83 or 50 nm), and a picosecond x-ray backlighter source. The short-pulse backlighter probed the aluminum plasma at different times by adjusting the delay between the two femtosecond driving beams. Absorption x-ray spectra at early times are characteristic of a dense and rather homogeneous plasma. Collisional-radiative atomic physics coupled with hydrodynamic simulations reproduce fairly well the measured average ionization as a function of time.

A cryogenically cooled Ti:sapphire regenerative ring amplifier was developed as a laser for generating a laser-produced plasma light source. With a 10 kHz 180 W pump laser, the amplifier output is 40 W before compression and 26 W after compression. We believe it to be the current highest average-power output from a single stage Ti:sapphire amplifier. The effective focal length of the thermal lens is measured to be 2.2 m at 100 K for 180 W of pump power. With a 1 m focal length lens placed in the resonator, the effect of a thermal lens on the resonator mode is suppressed. High conversion efficiency is achieved for the whole pumping power range without any additional measures for thermal compensation.

The experiments of flyer acceleration by the irradiation of a high power laser are carried out using the ASHURA system at the Electrotechnical Laboratory, in which the laser has a short wavelength (∼249 nm) and a long pulse duration (∼30 ns). Three-layered targets (aluminum–polyimide–tantalum) are irradiated. The laser ablates the aluminum and polyimide layers and the rear layer (tantalum) is accelerated as a flyer. It is suggested that the tantalum flyer is in a condensed state for the duration of flight. The flyer velocity estimated from the acceleration profile is at least 8 km/s. One-dimensional numerical simulation indicates that the terminal flyer velocity becomes higher than 15 km/s. The energy conversion from laser energy to flyer kinetic energy is more efficient than that in the previous experiments using the three-layered targets with a longer wavelength and a shorter pulse duration (1–2 ns). Thus, it is found that a facility with a long pulse duration and a short wavelength is suitable for the realization of a fast flyer keeping its state in a condensed phase.

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