A kilo-tesla level, quasi-static magnetic field (B-field), which is generated with an intense laser-driven capacitor-coil target, was measured by proton deflectometry with a proper plasma shielding. Proton deflectometry is a direct and reliable method to diagnose strong, mm3-scale laser-produced B-field; however, this was not successful in the previous experiment. A target-normal-sheath-accelerated proton beam is deflected by Lorentz force in the laser-produced magnetic field with the resulting deflection pattern recorded on a radiochromic film stack. A 610 ± 30 T of B-field amplitude was inferred by comparing the experimental proton pattern with Monte-Carlo calculations. The amplitude and temporal evolutions of the laser-generated B-field were also measured by a differential magnetic probe, independently confirming the proton deflectometry measurement results.

The Centro de Laseres Pulsados in Salamanca Spain has recently started operation phase and the first User access period on the 6 J 30 fs 200 TW system (VEGA 2) already started at the beginning of 2018. In this paper we report on two commissioning experiments recently performed on the VEGA 2 system in preparation for the user campaign. VEGA 2 system has been tested in different configurations depending on the focusing optics and targets used. One configuration (long focal length f=130 cm) is for under-dense laser-matter interaction where VEGA 2 is focused onto a low density gas-jet generating electron beams (via laser wake field acceleration mechanism) with maximum energy up to 500 MeV and an X-ray betatron source with a 10 keV critical energy. A second configuration (short focal length f=40 cm) is for over-dense laser-matter interaction where VEGA 2 is focused onto an 5 µm thick Al target generating a proton beam with a maximum energy of 10 MeV and average energy of 7-8 MeV and temperature of 2.5 MeV. In this paper we present preliminary experimental results.

for an Invited Paper for the DPP15 Meeting of the American Physical SocietyWe report on progresses of the Fast Ignition Realization Experiment (FIREX) project that has been curried out at the Institute of Laser Engineering to assess the feasibility of high density core heating with a high-power, short-pulse laser including the construction of the Kilo-Joule, Petawatt class LFEX laser system. Our recent studies identify three scientific challenges to achieve high heating efficiency in the fast ignition (FI) scheme with the current GEKKO and LFEX laser systems: (i) control of energy distribution of relativistic electron beam (REB), (ii) guiding and focusing of REB to a fuel core, and (iii) formation of a high areal-density core. The control of the electron energy distribution has been experimentally confirmed by improving the intensity contrast of the LFEX laser up to >10 9 and an ultra-high contrast of 10 11 with a plasma mirror. After the contrast improvement, 50% of the total REB energy is carried by a low energy component of the REB, which slope temperature is close to the ponderomotive scaling value (∼ 1 MeV). To guide the electron beam, we apply strong external magnetic field to the REB transport region. Guiding of the REB by 0.6 kT field in a planar geometry has already been demonstrated at LULI 2000 laser facility in a collaborative experiment lead by CELIA-Univ. Bordeaux. Considering more realistic FI scenario, we have performed a similar experiment using the Kilo-Joule LFEX laser to study the effect of guiding and magnetic mirror on the electron beam. A high density core of a laser-imploded 200 µm-diameter solid CD ball was radiographed with picosecond LFEX-produced K-alpha backlighter. Comparisons of the experimental results and integrated simulations using hydrodynamic and electron transport codes suggest that 10% of the efficiency can be achievable with the current GEKKO and LFEX laser system with the success of the above challenges.

We describe an experiment performed at the LULI laser facility using an advanced radiographic technique that allowed obtaining 2D, spatially resolved images of a shocked buried-code-target. The technique is suitable for applications on Fast Ignition as well as Warm Dense Matter research. In our experiment, it allowed to show cone survival up to Mbar pressures and to measure the shock front velocity and the fluid velocity associated to the laser-generated shock. This allowed obtaining one point on the shock polar of porous carbon.

We present experimental and numerical results on intense-laser-pulse-produced fast electron beams transport through aluminum samples, either solid or compressed and heated by laser-induced planar shock propagation. Thanks to absolute K yield measurements and its very good agreement with results from numerical simulations, we quantify the collisional and resistive fast electron stopping powers: for electron current densities of % 8 Â 10 10 A=cm 2 they reach 1:5 keV= m and 0:8 keV= m, respectively. For higher current densities up to 10 12 A=cm 2 , numerical simulations show resistive and collisional energy losses at comparable levels. Analytical estimations predict the resistive stopping power will be kept on the level of 1 keV= m for electron current densities of 10 14 A=cm 2 , representative of the full-scale conditions in the fast ignition of inertially confined fusion targets. In the fast ignition (FI) scheme of inertial confinement fusion, a relativistic electron beam (REB) heats the compressed core and ignites the fusion reactions in a capsule of deuterium and tritium [1]. This REB is generated at the critical density surface, or at the cone tip of a cone-embedded imploded capsule [2] by a high-intensity (% 10 20 W=cm 2 ) and high-energy ($100 kJ) laser. The REB source has a total kinetic energy & 40% of the laser energy [3][4][5] and a mean kinetic energy of 1-2 MeV (to provide an efficient coupling to the dense core). The REB transports energy from the generation region (with density and temperature in the level of a few g=cm 3 and a few eV, respectively) to the high-density ($ 400 g=cm 3 ) and hightemperature ($ 300 eV) core, where it must deliver a minimum of 20 kJ to heat the fuel to thermonuclear temperatures ($ 5-10 keV) [6]. The energy transport efficiency can be limited by such physical processes as collisional or collective energy loss [7], divergence [8,9], filamentation [10][11][12], etc. The energy losses over the highly inhomogeneous electron transport zone should be accurately predicted for a successful full-scale FI design. In particular, the REB stopping power should be limited to a few keV= m over the $100 m standing-off distance between the REB source and the imploded core.The work presented here aims at characterizing the REB stopping power in dense media in underscaled experimental conditions. The measurements are used to benchmark a REB transport code. The tested transport media, ranging from solid to warm dense matter, are much denser than the injected REB, being reasonable to assume an efficient neutralization of the injected current (j h ) by a counterstreaming current (j e ) of background thermal electrons (j h % Àj e ). Under these conditions, the numerical description of the REB transport often uses the so-called hybrid approach, where the incident and weakly collisional electrons are modeled kinetically and the highly collisional return current is described as an inertialess fluid [10,13,14].Most of the REB transport experiments carried out up to now have used solid targets [8,15...