Generation of picosecond hard-x-ray pulses in a femtosecond-laser-driven x-ray diode.

The temporal characteristics of ultrashort hard-x-ray pulses generated in a femtosecond-laser-driven x-ray diode are investigated for what is believed to be the first time. Copper Kalpha x-ray pulses with a duration of a few picoseconds are measured with a jitter-free x-ray streak camera.

Preplasma conditions for operation of 10-Hz subjoule femtosecond-laser-pumped nickel-likex-ray lasers.

We present measurements of electron densities of plasmas with femtosecond (fs) temporal resolution. The plasmas are generated by laser pulses with different intensities at different time delays. Such plasmas are of great interest as preplasmas for transient, collisionally excited x-ray lasers. The laser pulses producing the plasmas are generated by stretching part of a 130-fs laser pulse of the ATLAS titanium-sapphire laser of our institute and focusing this radiation to a line on molybdenum and silver slab targets. The electron density is measured as a function of distance from the target by interferometry using a Wollaston prism. Using an ultrashort probe pulse allows one to obtain data extremely close, about 10 microm, to the target surface. Experimental data are compared with simulations using the MULTI hydrocode. The results allow comparison of the ablation from a hard (Mo) and a soft (Ag) material, optimization of prepulse-main pulse delay times, and selection of the best pump geometry allowing for propagation of the pump and x-ray beams. These points are key elements for the development of a high-repetition-rate soft-x-ray laser.