Enhanced hot electron generation at relativistic interaction of femtosecond pulses with nanoscale structured targetsтезисы доклада Тезисы

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[1] Enhanced hot electron generation at relativistic interaction of femtosecond pulses with nanoscale structured targets / K. A. Ivanov, I. Mordvintsev, P. Danilov et al. // Book of abstracts of the 34-th European Conference on Laser Interaction with Matter (ECLIM2016). — Москва, 2016. In this work we present our new experimental and numerical findings on high intensity (over 1018 W/m2) femtosecond interaction with nanostructured targets. We demonstrate, that the hot electron production and X-ray generation may be significantly enhanced when a nanostructured silicon, metal or carbon targets are utilized compared to the initially flat substrate. The modification of the target surface was made by electrochemical etching in case of silicon and by laser ablation for metal. Varying the parameters the structures with different shape and size (subwavelength nanograss, nanopores, bubbles, cones) could be obtained. The advantage of these methods is that it allows formation of large area samples with high repetitively suitable for laser-plasma experiments with high repetition rate. We also used thick layer of carbon nanotubes as target. The targets were irradiated by a Ti:Sa laser pulses (=50 fs, E>10 mJ, 10 Hz, Ipeak>1018 W/cm2) with the contrast additionally cleaned by the XPW technique to avoid the structures damage by the prepulses (ASE pedestal ratio of the pulse exceeds 109). We found that the temperature of the hot electron temperature in plasma increases several times (from ∼150 keV for flat metal and silicon substrate to a maximum of almost 700 keV for the nanostructured material). It is worth mention, that the hot electron temperature is very sensitive to the shape of the structures. The energy growth effect is higher for nanograss target obtained with longer etching time (i.e. longer silicon wires) and less pronounced for porous target. For the metal target the size of the nanostructures is found to play a significant role. The PIC simulation of laser-plasma interaction revealed that the electron energy increase may be explained by the enhanced absorption and acceleration of particles in the complex field formed onto the structures. This work was supported by the RFBR grant #15-02-08113-a and by RSF grant #14-12-00194.

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