Increased x-ray conversion efficiency from ultra high contrast, relativistic laser pulse irradiation of large aspect ratio, vertically aligned nanowires
ORAL
Abstract
Recent experiments at Colorado State University have shown that the effective trapping of clean, Joule-level fs laser pulses of relativistic intensity in arrays of high aspect ratio aligned nanowire creates multi-kev, near solid density, large scale (\textgreater 4um deep) plasmas. The drastically decreased radiative life time and increased hydrodynamic cooling time from these plasmas increases the x-ray conversion efficiency. We measured a record conversion efficiency of \textasciitilde 10{\%} into hv\textgreater 1KeV photons (2pi steradians), and of 0.3{\%} for hv\textgreater 6KeV. The experiments used Au and Ni nanowires of 55nm, 80nm and 100nm in diameter with 12{\%} of solid density irradiated by high contrast (\textgreater 10$^{\mathrm{12}})$ pulses of 60fs FWHM duration from a frequency doubled Ti:Sa laser at intensities of I$=$5x10$^{\mathrm{19}}$Wcm$^{\mathrm{-2.\thinspace }}$We also present preliminary results on x-ray emission from Rhodium nanowires in the 19-22KeV range and demonstrate the potential of this picosecond X-ray source in flash radiography.
*This work was supported by the Fusion Energy Program, Office of Science of the U.S Department of Energy, and by the Defense Threat Reduction Agency grant HDTRA-1-10-1-0079.
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