Bright X-ray Sources from Ultra-high Density Matter in Volumetrically Heated Nanowire Arrays*

Trapping femtosecond laser pulses of relativistic intensity within ordered nanowire arrays results in the volumetric heating of matter to multi-KeV, near solid density plasmas. Using high contrast pulses of 60fs FWHM duration from a frequency doubled Ti:Saph laser, we irradiated arrays of 55nm and 80nm diameter Au and Ni targets with 12{\%} of solid density at intensities of 5x10$^{18}$ Wcm$^{-2}$. We observed strong He-like line emission that surpassed the characteristic K-a emission by an order of magnitude. The Au nanowire spectrum displayed strong Au M-shell emission with unresolved 4-3 lines from ions ranging from Co-like to Ga-like Au. Filtered photodiode measurements show a $\sim$ 100x emission increase with respect to smooth solid targets for photon energies \textgreater 9keV.