PIC simulation geometry for sinusoidal surface features. The laser (polarized along the z-axis) is normally incident propagating from left to right where LA (TN) is the Laser-Axis (target-normal). The laser focal plane and (mean) surface interface is located at . Sinusoidal surface perturbations have spatial periodicity and peak-to-trough height H.
Temporal evolution perfectly flat interface, surface (a) with (i) the electron density (log10), (ii) By (linear) and (iii) angular distributions (normalized) resolved by energy. The first column is a snapshot in time at the rising half peak, the middle column at the peak of the pulse, and the third the falling half peak. Vertical solid (dashed) black curves in (i) and (ii) are relativistic (original) surface and the horizontal dashed white lines in (iii) indicate (lower) and (upper).
Hot-electron phase space calculations of the point source test particles accelerated from solid density by standing-wave EM fields as a function of final kinetic energy and angle (colored by initial kinetic energy) for (ia) a perfect conductor and (ib) plasma with the skin effect included. (ii) Initially electrons from different density interfaces (relative to initial solid density at ). The horizontal dashed white lines indicate (lower) and (upper).
Same as Fig. 2 but for surface (b).
Typical hot electron trajectories, colored by instantaneous kinetic energy, from the (ia) perfectly flat interface, (ib) optically flat interface, and (ii) total travel distances in vacuum as a function of maximum kinetic energy gained. The vertical dashed black lines indicate (left) and (right).
(i) Energy distribution of electrons that pass plane inside solid density on a log-linear scale for surfaces (a) through (d). The solid black line is a Boltzmann distribution with temperature equal to (arbitrary normalization). (ii) Same distributions but with single temperature Boltzmann fit to hot-tail subtracted. The vertical dashed black lines indicate (left) and (right).
Same as Fig. 2 but for surface (c). The solid white curves in (iii) indicate the classical ejection angle.
Same as Fig. 2 but for surface (d).
Conversion efficiency of surface features addressed in this study.
Estimated conversion efficiency contributions from sharp interface standing-wave accelerations (SW) and under-dense traveling wave accelerations (TW).
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