Laser irradiation of thin films: Effect of energy transformation

Abstract

The irradiation of thin films by intensive subpicosecond laser pulses with nanosecond prepulse is accompanied by a number of various physical processes. The laser beam transmissions through the film as well as the re-emission flux on both sides of the film plasma have been evaluated by simulation for Al and CH2 materials. It has been demonstrated that the thickness of the film can be chosen to cut off the long nanosecond prepulse whereas the main pulse is transmitted through the plasma. Thus, thin films can be useful for the laser contrast improvement in experiments with different targets.Nevertheless, the laser energy transformation into the soft X-ray radiation on the back side of the shielding film plasma can reach up to 7% of the incident intensity for the Al film and result in strong preheating of the target. At the same time the re-emission flux produced by a CH2 film is an order lower than that in the case of Al film. The shielding of an Ag bulk target by Al and CH2 films is simulated and discussed.

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

“…To describe plasma corona formation under the action of different intensity prepulses, the 1D version (Povarnitsyn et al, 2013) of the HELIO2D code (Andreev et al, 2015) was used, which takes into account 1D hydrodynamic motion of matter, laser energy absorption, two-temperature nonequilibrium states for electron and ion subsystems, electron thermal conductivity, and radiation transport in diffusion approximation. The evolution of material parameters is described using the conservation of mass, momentum, and energy of electron and ion subsystems in a single-fluid twotemperature Lagrangian form.…”

“…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.…”

“…A typical time structure of the petawatt class laser pulse is shown in Figure 4 of (Wagner et al, 2014b), where the pulse shape of the PHELIX laser at the first harmonic, λ 0 = 1.053 μm, is shown for different parameters of the contrast boosting module. For simulation of the laser-matter interaction at non-relativistic prepulse intensities, we have elaborated and used the two-temperature single-fluid radiation hydrodynamic model (Povarnitsyn et al, 2012a(Povarnitsyn et al, , 2013. 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.…”

“…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.…”

Interaction of annular-focused laser beams with solid targets

“…Previously, we developed and used for modeling of laser-matter interaction a wide-range 1D hydrodynamic model (Andreev et al, 2003;Veysman et al, 2006;Agranat et al, 2007;Povarnitsyn et al, 2013;2012a;2012b). Processes, considered in this paper are essentially multi-dimensional and our present approach is based on the 2D hydrodynamics completed with wide-range models of laser energy absorption, ionization, and radiation losses in plasma and electron-ion coupling (Povarnitsyn et al, 2012a;2012b;.…”