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We report what is to our knowledge the first demonstration of spatial filtering of a high-order harmonic beam into a soft-x-ray laser plasma amplifier at 32.8 nm. After amplification the seed energy is enhanced by a factor of 50, and the beam profile of the amplified beam exhibits an Airy-like shape due to the spatial filtering by the optical field ionized plasma. Moreover, the transverse coherence of the spatially filtered amplified beam is strongly enhanced, resulting in the generation of a peak coherent power of 0.9 x 10(5) to 1.8 x 10(5) W.

International audienceThe evolution with time of the ion temperature of a xenon gas during and after the irradiation with a high intensity laser beam is determined. The processes taken into account are (i) direct interaction with the laser beam, (ii) binary collisions with hot electrons, (iii) contribution with the electrostatic wakefield, (iv) hydrodynamic expansion and (v) transfer of potential to kinetic energy among the plasma ions. It is shown that, because the ions are strongly coupled, the last process is by far the most efficient one. Using the One Component Plasma (OCP) model, a simple analytical formula for the ion temperature at equilibrium is obtained. Application of this work to the development of soft x-ray laser sources is stressed out