Nanostructure array plasmas generated by femtosecond pulses at highly relativistic intensities
ORAL
Abstract
The irradiation of high aspect ratio ordered nanostructure arrays with ultra-high contrast femtosecond laser pulses of relativistic intensity provides a unique combination of nearly complete optical absorption and drastically enhanced light penetration into near-solid density targets. This allows the material to be volumetrically heated deep into the ultra-high energy density regime$^{\mathrm{1}}$. In previous experiments we have shown that irradiation of Ni and Au nanostructures with femtosecond pulses focused to an intensity of 5x10$^{\mathrm{18}}$ Wcm$^{\mathrm{-2}}$ generate multi-KeV near solid density plasmas in which atoms are ionized to the Ni$^{\mathrm{+26}}$ and Au$^{\mathrm{+52}}$ charge states$^{\mathrm{2}}$. Here we present the first results of the irradiation of nanostructure arrays with highly relativistic pulses of intensities up to 5x10$^{\mathrm{21}}$Wcm$^{\mathrm{-2}}$. Silver and Rhodium nanowire arrays were irradiated with frequency-doubled pulses of 30 fs duration from a petawatt-class Ti:Sa laser. Time integrated x-ray spectra show the presence of He-like and Li-like emission. Results of experiments conducted with a variety of different nanowires diameters with a range of interwire spacings will be presented and compared to the result of 3D particle-in-cell-simulations. $^{\mathrm{1}}$Bargsten et al Sci. Advances Vol.3 No.1 (2017) $^{\mathrm{2}}$Purvis et al Nature Photonics 7, 769 (2013).
*This work was supported by the Fusion Energy Program, Office of Science of the U.S Department of Energy
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