Dynamics of thin metal foils irradiated by moderate-contrast high-intensity laser beams

Abstract

Laser contrast is a crucial parameter in experiments with high-intensity high-energy pulses. For relativistic intensities of the main pulse & 10 19 W=cm 2 , even high-contrast beams can produce plasma on the target surface due to a long nanosecond prepulse action which results in an undesirable early smearing of the target. In particular, dynamics of thin foils under the prepulse action is especially important for the laser ion acceleration technique and x-rays generation. To avoid the influence of the long laser prepulse, a thin foil can be arranged in front of the target. The analysis of the multi-stage foil dynamics is performed using a wide-range two-temperature hydrodynamic model, which correctly describes the foil expansion starting from the normal solid density at room temperature. Simulations show that varying the foil thickness, one can diminish the prepulse transmission through the foil material in many orders of magnitude and at the same time provide the total transparency of the foil plasma by the moment of the main high-intensity ultrashort pulse arrival. Modeling of shielded and unshielded target dynamics demonstrates the effectiveness of this technique. However, the prepulse energy re-emission by the shielding foil plasma can be sizable producing an undesirable early heating of the target placed behind the foil. V

Dielectric function of a collisional plasma for arbitrary ionic charge

“…(2) and (3) contain the inverse Z −1 of the ionic charge number Z. Hence, these terms vanish at the limit Z ≫ 1 of the highly ionized ions and one arrives at the Lorentz plasma model [22] in this case, which is frequently used in hydrodynamic codes due to its simplicity [9][10][11][12][13].…”

“…Currently various models of these interactions are widely discussed (see, e.g., Refs. [8][9][10][11][12][13] and references therein). The key quantity which characterizes laser-matter interaction as well as the optical properties of the matter is the plasma dielectric function (permittivity) ε, which determines the electrodynamic response of the system on perturbations.…”

Electron acceleration at grazing incidence of a subpicosecond intense laser pulse onto a plane solid target

“…This wide-range model describes laser energy absorption, electron-ion coupling and two-temperature effects, radiation transport, thermodynamic properties of materials, and ionization from normal conditions at room temperature to weakly non-ideal high-temperature plasma. Using the model we have studied pump-probe experiments (Povarnitsyn et al, 2012a) as well as the action of a nanosecond prepulse on thin films (Povarnitsyn et al, 2012b(Povarnitsyn et al, , 2013. As opposed to the Radiative Arbitrary Lagrangian-Eulerian Fluid dynamics in two dimensions code (Ortner et al, 2015), in our model, the laser absorption is described using the wave equation for the laser pulse electric field.…”

“…For relativistic intensities of a main subpicosecond pulse, even high-contrast beams can produce plasma on a target surface due to a long nanosecond and picosecond prepulses impact, which results in target surface modifications before the main pulse action, and influences the subpicosecond pulse interaction with the target extremely (Povarnitsyn et al, 2012b(Povarnitsyn et al, , 2013Esirkepov et al, 2014). In this paper, the generation of hot electrons at grazing incidence of a subpicosecond intense laser pulse onto a plane solid target is analyzed for the parameters of the petawatt high-energy laser for heavy ion experiments (PHELIX) (Bagnoud et al, 2010;Wagner et al, 2014a) using three-dimensional (3D) particle-in-cell (PIC) modeling (Pukhov, 1999) and a wide-range hydro modeling (Povarnitsyn et al, 2012a) of the preplasma expansion under the action of the laser prepulse.…”

Simulation of laser ablation of metals for nanoparticles production

“…7 The viscosity and thermal conductivity of the ions are neglected in this model. To calculate the ablation depth, we perform an integration of the mass flux through the surface using the expression:…”