Absorption of Ultrashort Laser Pulses and Particle Transport in Dense Targets

The interaction of short laser pulses with solid density targets has been studied in numerous experiments and by theoretical and computational modelling. The absorption of laser energy and transport of heat into dense plasmas is central to the understanding of such interactions. For moderate laser intensities, I..2<1017 W m2/cm2, hydrodynamic simulations [1,2] have properly reproduced experimental results. At higher laser fluxes collisionless absorption mechanisms and the generation and transport of relativistic electrons become important and therefore kinetic models have to be used to describe laser plasma coupling. We report in this paper on the test case study of laser pulse absorption by a steep density profile plasma using the new kinetic code, KALOS [3]. We have modelled absorption and electron transport at normal laser incidence and maximum intensity I0=1015 W/cm2 in a high density Al plasma. Several kinetic effects related to the non-Maxwellian electron distribution function (EDF) and reduced thermal transport have been observed in the simulations already at this moderate intensity which was previously considered in the hydrodynamic description [2]. (Author)