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The field of laser-matter interaction has branched out in two main directions. The first, motivated by laser inertial confinement fusion, warm-dense-matter, fast ignition and astrophysics in laboratory, and the second driven by ultra-high intensity, exotic physics, high-energy particle, photon beam generation and time-resolved attosecond (zeptosecond) science. The degree of maturity from both experimental and theoretical stand-points is such that a large European infrastructure for each branch is contemplated as part of the European Roadmap. The first one, HiPER-PETAL will be dedicated to fast ignition with the aim of obtaining a thermonuclear gain of 100, whereas the second, Extreme Light Infrastructure (ELI) could go beyond the relativistic regime to foray into the ultra-relativistic domain >1024 W cm[?]2. In this paper we highlight the intriguing perspectives that these two projects will offer. [ABSTRACT FROM AUTHOR]

Saturation of electron plasma waves excited by a spatially localized driver and the electron acceleration in these plasma waves are studied by means of numerical simulations. The model consists of the set of Zakharov equations for the electron plasma and ion acoustic waves coupled to the quasi-linear equation for the electron distribution function. The saturation levels of both electron plasma and ion acoustic waves and the number and energy of hot electrons are studied in function of the driver wave number and amplitude and the size of the excitation region. A correlation between the onset of the strong Langmuir turbulence and the efficient electron heating is discussed. [ABSTRACT FROM AUTHOR]

Low density foams are widely used for laser plasma interaction studies. Here, we present the results of first direct measurements of a residual level of inhomogeneity of a foam plasma by using a pump-probe technique. It is demonstrated that large scale density modulations in such a plasma can survive a time larger than 1 ns, much longer than the plasma formation time. [ABSTRACT FROM AUTHOR]

Laser ponderomotive self-focusing in an underdense homogeneous plasma is studied within the paraxial complex geometrical optics (PCGO) approach implemented in a hydrodynamic code in two-dimensional planar geometry. The self-focusing of a PCGO Gaussian beam is compared to simulations performed with a paraxial electromagnetic code. Good agreement has been found for beam powers less than three times the critical power and for plasma densities 5%–10% of the critical density. Besides Gaussian beams, PCGO allows to reproduce spatially modulated beams by superposition of Gaussian beams, mimicking a speckle pattern. Although the statistics of speckle patterns generated with PCGO reproduces well the speckle statistics of optically smoothed beams, a PCGO speckle is larger than optical speckles, carrying thus higher power such that they overestimate self-focusing effects. To overcome this issue, an algorithm is proposed within PCGO framework: it consists of superposing several Gaussian beams forming a speckle such that self-focusing effects are eventually well controlled. It is found that the superposition of three Gaussian beams with appropriate initial conditions leads to a reduction of the PCGO speckle intensity enhancement. [ABSTRACT FROM AUTHOR]

Efficient electron acceleration and heating is demonstrated in a multimode structure created by interference of several laser beams of a relativistic intensity and a picosecond duration near a sharp target boundary. Electron energization proceeds in two steps, with a slow stochastic heating followed by a fast regular acceleration in a resonance interaction with one of wave packets. It results in formation of a population of energetic electrons with an exponential distribution in energy characterized by a high effective temperature and a sharp cutoff. Hot electron characteristics depend on the number of crossing laser beams and their respective angles. This process is an example of efficient electron heating in vacuum by electromagnetic fields without participation of electrostatic plasma waves. It might contribute to creation of a superthermal particle population with an effective temperature significantly exceeding the common ponderomotive scaling. [ABSTRACT FROM AUTHOR]

The possibility of achieving a pair beaming in the Breit–Wheeler (BW) electron/positron pair creation process is investigated in this paper. We examine the effect of the BW differential cross section on the pair’s angular and energy distributions. Although this study is relevant for laser induced intense gamma-ray source collision experiments, we apply this pair beaming effect in an astrophysical context, in particular for active galactic nuclei (AGN). [ABSTRACT FROM AUTHOR]

The advent of high-power lasers facilities such as the National Ignition Facility (NIF) and the laser megajoule provide unique platforms to study the physics of turbulent mixing flows in high energy density plasmas. We report here on the commissioning of a novel planar direct-drive platform on the NIF, which allows the acceleration of targets during 30 ns. Planar plastic samples were directly irradiated by 300–450 kJ of UV laser light (351 nm) and a very good planarity of the laser drive is demonstrated. No detrimental effect of imprint is observed in the case of these thick plastic targets (300 μm), which is beneficial for future academic experiments requesting similar irradiation conditions. The long-duration direct-drive (DD) platform is thereafter harnessed to study the ablative Rayleigh–Taylor instability (RTI) in DD. The growth of two-dimensional pre-imposed perturbations is quantified through time-resolved face-on x-ray radiography and used as a benchmark for radiative hydrocode simulations. The ablative RTI is then quantified in its highly nonlinear stage starting from intentionally large 3D imprinted broadband modulations. Two generations of bubble mergers is observed for the first time in DD, as a result of the unprecedented long laser acceleration. [ABSTRACT FROM AUTHOR]

The pair creation from the Breit–Wheeler process is one of the basic processes in the universe. Laser induced intense γ-ray sources will allow a direct observation of this process in the laboratory for the first time. In this paper we demonstrate the effect of pair beaming in the collision of two photon beams which may facilitate the experimental observation of the Breit–Wheeler process. [ABSTRACT FROM AUTHOR]

The shock ignition scheme is an alternative approach, which aims to achieve ignition of fusion reactions in two subsequent steps: first, the target is compressed at a low implosion velocity and second, a strong converging shock is launched during the stagnation phase and ignites the hot spot. In this paper we describe the major elements of this scheme and recent achievements concerning the laser-plasma interaction, the crucial role of hot electrons in the shock generation, the shock amplification in the imploding shell and the ignition conditions. [ABSTRACT FROM AUTHOR]