Intense picosecond x-ray pulses from laser plasmas by use of nanostructured "velvet" targets

We describe the optical, radiative, and laser-plasma physics of a new type of nanostructured surface especially promising as a very high absorption ta rget for high-peak-power subpicosecond laser-matter interaction. This orien ted-nanowire material, irradiated by 1 ps pulses at intensities up to 10(17 ) W cm(-2) produces picosecond soft x-ray pulses 50X more efficiently than do solid targets. We compare this to "smoke" or metallic clusters, and soli d nanogroove-grating surfaces; the "metal-velvet" targets combine the high yield of smoke targets with the brief emission of grating surfaces.