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We report results and modelling of an experiment performed at the Target Area West Vulcan laser facility, aimed at investigating laser–plasma interaction in conditions that are of interest for the shock ignition scheme in inertial confinement fusion (ICF), that is, laser intensity higher than 1016 W/cm2 impinging on a hot (T > 1 keV), inhomogeneous and long scalelength pre-formed plasma. Measurements show a significant stimulated Raman scattering (SRS) backscattering (∼ 4%−20% of laser energy) driven at low plasma densities and no signatures of two-plasmon decay (TPD)/SRS driven at the quarter critical density region. Results are satisfactorily reproduced by an analytical model accounting for the convective SRS growth in independent laser speckles, in conditions where the reflectivity is dominated by the contribution from the most intense speckles, where SRS becomes saturated. Analytical and kinetic simulations well reproduce the onset of SRS at low plasma densities in a regime strongly affected by non-linear Landau damping and by filamentation of the most intense laser speckles. The absence of TPD/SRS at higher densities is explained by pump depletion and plasma smoothing driven by filamentation. The prevalence of laser coupling in the low-density profile justifies the low temperature measured for hot electrons (7−12 keV), which is well reproduced by numerical simulations.

In this paper we report the measurement of laser-driven proton acceleration obtained by irradiating nanotube array targets with ultrashort laser pulses at an intensity in excess of 1020 W cm-2. The energetic spectra of forward accelerated protons show a larger flux and a higher proton cutoff energy if compared to flat foils of comparable thickness. Particle-In-Cell 2D simulations reveal that packed nanotube targets favour a better laser-plasma coupling and produce an efficient generation of fast electrons moving through the target. Due to their sub-wavelength size, the propagation of e.m. field into the tubes is made possible by the excitation of Surface Plasmon Polaritons, travelling down to the end of the target and assuring a continuous electron acceleration. The higher amount and energy of these electrons result in turn in a stronger electric sheath field on the rear surface of the target and in a more efficient acceleration of the protons via the target normal sheath acceleration mechanism.

This paper describes the results of a series of experiments conducted with the PALS laser at intensities of interest for the shock ignition approach to inertial fusion. In particular, we addressed the generation of hot electrons (HE) (determining their average energy and number), as well as the parametric instabilities which are producing them. In addition, we studied the impact of HE on the formation and dynamics of strong shocks.

This paper describes the results of a series of experiments conducted with the PALS laser at intensities of interest for the shock ignition approach to inertial fusion. In particular, we addressed the generation of hot electrons (HE) (determining their average energy and number), as well as the parametric instabilities which are producing them. In addition, we studied the impact of HE on the formation and dynamics of strong shocks.

We present the results of an experiment on laser-driven shock waves performed at the Prague Asterix Laser system (PALS), where the fundamental frequency of the laser (1315 nm) is used to launch a strong shock in planar geometry. The experiment aims to characterize both shock waves and hot electrons generated at intensities of ’ 1016 W=cm2 . It is shown that, in these interaction conditions, hydrodynamics is strongly impacted by noncollisional mechanisms, and the role of the hot electrons, generated by parametric instabilities, is essential in determining shock dynamics.

We report on the development of a Monte Carlo application, based on the GEANT4 toolkit, for the characterization and optimization of electron beams for clinical applications produced by a laser-driven plasma source. The GEANT4 application is conceived so as to represent in the most general way the physical and geometrical features of a typical laser-driven accelerator. It is designed to provide standard dosimetric figures such as percentage dose depth curves, two-dimensional dose distributions and 3D dose profiles at different positions both inside and outside the interaction chamber. The application was validated by comparing its predictions to experimental measurements carried out on a real laser-driven accelerator. The work is aimed at optimizing the source, by using this novel application, for radiobiological studies and, in perspective, for medical applications.

We report measurements of parametric instabilities and hot electron generation in a laser intensity regime up to 6 x 10(15) W/cm(2), typical of the shock ignition approach to inertial fusion. Experiments performed at the PALS laboratory in Prague show that the incident laser energy losses are dominated by Stimulated Brillouin Scattering (SBS) rather than by Stimulated Raman Scattering (SRS) or Two-Plasmon Decay (TPD). Results are compared to hydrodynamics simulations using a code that includes self-consistent calculations of non-linear laser plasma interactions and accounts for the laser intensity statistics contained in the beam speckles. Good agreement is found for the backscattered SRS light, and for temperature and flux of hot electrons. The effect of high-intensity speckles on backscattered SRS is also underlined numerically and experimentally. Copyright (C) EPLA, 2017

The new muon (g-2) experiment E989 at Fermilab will be equipped with a laser calibration system for all the 1296 channels of the calorimeters. An integrating sphere and an alternative system based on an engineered diffuser have been considered as possible light distributors for the experiment. We present here a detailed comparison of the two based on temporal response, spatial uniformity, transmittance and time stability., Comment: accepted to Nucl.Instrum.Meth. A