| Recent laser-ion acceleration experiments performed at the DRACO laser in Dresden, Germany, have demonstrated the importance of a precise understanding of the electron dynamics in solids on an ultra-short time scale. For example, with ultra-short laser pulses a description based purely on the evolution of a thermal electron ensemble, as in standard TNSA models, is not sufficient anymore. Rather, non-thermal effects during the ultra-short intra-pulse phase of laser-electron interaction in solids become important for the acceleration of ions when the laser pulse duration is in the order of only a few 10s of femtoseconds. While the established maximum ion energy scaling in the TNSA regime goes with the square root of the laser intensity, for such ultra short pulse durations the maximum ion energy is found to scale linear with laser intensity, motivating the interest in such laser systems. We present recent advances in the description of the laser interaction with solids, focusing on the implications of intra-pulse non-thermal phenomena and the electron average energy on the ion acceleration. We present a novel approach for an analytic electron temperature scaling model which can explain experimental results especially for ultra intense laser pulses where present scaling models apparently fail. Our findings are therefore crucial for the interpretation of experimental results and to predict the expected ion maximum energies for future laser systems. |
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