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Hot electron and x-ray production from solid targets coated with polystyrene-spheres which are irradiated with high-contrast, 100fs, 400nm light pulses at intensity up to 2×1017W∕cm2 have been studied. The peak hard x-ray signal from uncoated fused silica targets is an order of magnitude smaller than the signal from targets coated with submicron sized spheres. The temperature of the x-rays in the case of sphere-coated targets is twice as hot as that of uncoated glass. A sphere-size scan of the x-ray yield and observation of a peak in both the x-ray production and temperature at a sphere diameter of 0.26μm, indicate that these results are consistent with Mie enhancements of the laser field at the sphere surface and multipass stochastic heating of the hot electrons in the oscillating laser field. These results also match well with particle-in-cell simulations of the interaction.

Inverse problems in laser spectroscopy are reported to be successfully solved by application of artificial neural networks, a powerful data processing technique that performs better than traditional variation algorithms of solving inverse problems.Keywords: laser spectroscopy, inverse problems, artificial neural networks 157 Downloaded From: http://proceedings.spiedigitallibrary.org/ on 06/22/2016 Terms of Use: http://spiedigitallibrary.org/ss/TermsOfUse.aspx Proc. SPIE Vol. 4749 158 Downloaded From: http://proceedings.spiedigitallibrary.org/ on 06/22/2016 Terms of Use: http://spiedigitallibrary.org/ss/TermsOfUse.aspx

, "Generation of Mie size microdroplet aerosols with applications in laser-driven fusion experiments," Rev Sci. Instrum., 80, (2009 We have developed a tunable source of Mie scale microdroplet aerosols that can be used for the generation of energetic ions. To demonstrate this potential, a terawatt Ti: Al 2 O 3 laser focused to 2 ϫ 10 19 W / cm 2 was used to irradiate heavy water ͑D 2 O͒ aerosols composed of micron-scale droplets. Energetic deuterium ions, which were generated in the laser-droplet interaction, produced deuterium-deuterium fusion with approximately 2 ϫ 10 3 fusion neutrons measured per joule of incident laser energy.

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The optical conductivity of a dense femtosecond laser-heated aluminum plasma heated to 0.1-1.5 eV was measured using frequency-domain interferometry with chirped pulses, permitting simultaneous observation of optical probe reflectivity and probe pulse phase shift. Coupled with published models of bound-electron contributions to the conductivity, these two independent experimental data yielded a direct measurement of both real and imaginary components of the plasma conductivity.

X-ray yield measurements from targets coated with wavelength-scale spheres are compared with measurements from polished targets. Evidence for a hotter resonant electron temperature due to field enhancements from Mie resonances in the spheres is investigated.