Quasi-static magnetic-fields up to 800 T are generated in the interaction of intense laser pulses (500 J, 1 ns, − 10 W cm 17 2 ) with capacitor-coil targets of different materials. The reproducible magnetic-field peak and rise-time, consistent with the laser pulse duration, were accurately inferred from measurements with GHz-bandwidth inductor pickup coils (B-dot probes). Results from Faraday rotation of polarized optical laser light and deflectometry of energetic proton beams are consistent with the B-dot probe measurements at the early stages of the target charging, up to ≈ t 0.35 ns, and then are disturbed by radiation and plasma effects. The field has a dipole-like distribution over a characteristic volume of 1 mm 3 , which is consistent with theoretical expectations. These results demonstrate a very efficient conversion of the laser energy into magnetic fields, thus establishing a robust laser-driven platform for reproducible, well characterized, generation of quasi-static magnetic fields at the kT-level, as well as for magnetization and accurate probing of high-energy-density samples driven by secondary powerful laser or particle beams.

Powerful laser-plasma processes are explored to generate discharge currents of a few 100 kA in coil targets, yielding magnetostatic fields (B-fields) in excess of 0.5 kT. The quasi-static currents are provided from hot electron ejection from the laser-irradiated surface. According to our model, describing qualitatively the evolution of the discharge current, the major control parameter is the laser irradiance I las λ 2 las . The space-time evolution of the B-fields is experimentally characterized by high-frequency bandwidth B-dot probes and by proton-deflectometry measurements. The magnetic pulses, of ns-scale, are long enough to magnetize secondary targets through resistive diffusion. We applied it in experiments of laser-generated relativistic electron transport into solid dielectric targets, yielding an unprecedented 5-fold enhancement of the energy-density flux at 60 µm depth, compared to unmagnetized transport conditions. These studies pave the ground for magnetized high-energy density physics investigations, related to laser-generated secondary sources of radiation and/or high-energy particles and their transport, to high-gain fusion energy schemes and to laboratory astrophysics.

Intense lasers interacting with dense targets accelerate relativistic electron beams, which transport part of the laser energy into the target depth. However, the overall laser-to-target energy coupling efficiency is impaired by the large divergence of the electron beam, intrinsic to the laser–plasma interaction. Here we demonstrate that an efficient guiding of MeV electrons with about 30 MA current in solid matter is obtained by imposing a laser-driven longitudinal magnetostatic field of 600 T. In the magnetized conditions the transported energy density and the peak background electron temperature at the 60-μm-thick target's rear surface rise by about a factor of five, as unfolded from benchmarked simulations. Such an improvement of energy-density flux through dense matter paves the ground for advances in laser-driven intense sources of energetic particles and radiation, driving matter to extreme temperatures, reaching states relevant for planetary or stellar science as yet inaccessible at the laboratory scale and achieving high-gain laser-driven thermonuclear fusion.

We report on improved proton acceleration from the interaction of a short pulse high intensity laser (>10 20 Wcm −2 ) with nano-engineered targets. Planar targets (from 7 to 20 μm) with protruding gold nanowires having different total areal densities, lengths, and diameters, ranging from 3% to 60% of the size of the laser focal spot were used during an experimental campaign at the 3 J, 30 fs HERCULES laser facility. The results show the importance of the average number of nanowires per focal spot, N, on laser energy absorption. We show that the proton acceleration is significantly improved by using 1 nanowires per focal spot. Detailed analysis indicates that 1 nanowire per focal spot optimizes the interaction between laser pulse and nanowires, in which the wings of the pulse pull out electrons from the wires forming a plasma with density that allows for deep penetration of the laser pulse into the array. When moving away from this optimum in both directions, N=1 and N?1, the laser pulse-nanowire coupling is either too weak or unfavorable for obtaining maximum proton energy. Proton spectra are compared to simulations using 2D-3V particle-in-cell code which reproduces the experimental data with good agreement.

Thanks to their high dynamic range and ability to withstand electromagnetic pulse, imaging plates (IPs) are commonly used as passive detectors in laser-plasma experiments. In the framework of the development of the diagnostics for the Petawatt Aquitaine Laser facility, we present an absolute calibration and spatial resolution study of five different available types of IP (namely, MS-SR-TR-MP-ND) performed by using laser-induced K-shell X-rays emitted by a solid silver target irradiated by the laser ECLIPSE at CEntre Lasers Intenses et Applications. In addition, IP sensitivity measurements were performed with a 160 kV X-ray generator at CEA DAM DIF, where the absolute response of IP SR and TR has been calibrated to X-rays in the energy range 8-75 keV with uncertainties of about 15%. Finally, the response functions have been modeled in Monte Carlo GEANT4 simulations in order to reproduce experimental data. Simulations enable extrapolation of the IP response functions to photon energies from 1 keV to 1 GeV, of interest, e.g., for laser-driven radiography.

We present the results of the first commissioning phase of the short-focal-length area of the Apollon laser facility (located in Saclay, France), which was performed with the first available laser beam (F2), scaled to a nominal power of 1 PW. Under the conditions that were tested, this beam delivered on-target pulses of 10 J average energy and 24 fs duration. Several diagnostics were fielded to assess the performance of the facility. The on-target focal spot and its spatial stability, the temporal intensity profile prior to the main pulse, and the resulting density gradient formed at the irradiated side of solid targets have been thoroughly characterized, with the goal of helping users design future experiments. Emissions of energetic electrons, ions, and electromagnetic radiation were recorded, showing good laser-to-target coupling efficiency and an overall performance comparable to that of similar international facilities. This will be followed in 2022 by a further commissioning stage at the multi-petawatt level.

Multimegabar laser-driven shock waves are unique tools for studying matter under extreme conditions. Accurate characterization of shocked matter is for instance necessary for measurements of equation of state data or opacities. This paper reports experiments performed at the LULI facility on the diagnosis of shock waves, using x-ray-absorption radiography. Radiographs are analyzed using standard Abel inversion. In addition, synthetic radiographs, which also take into account the finite size of the x-ray source, are generated using density maps produced by hydrodynamic simulations. Reported data refer to both plane cylindrical targets and hemispherical targets. Evolution and deformation of the shock front could be followed using hydrodynamic simulations.

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