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We detail results of an experiment performed at the Ligne d'Intégration Laser facility aimed at studying supersonic and diffusive radiation front propagation in low-density SiO2 aerogel (20 and 40 mg/cm3) enclosed in a gold tube, driven by thermal emission from a laser-heated spherical gold cavity. The evolution of the front is studied continuously by measuring its self-emission with a 1D (one-dimensional) time-resolved soft x-ray imager. Measurement is performed along (through a 200- μm-wide observation slit) and at the exit of the tube giving access to the dynamics and the curvature of the front. Experimental results are then compared successfully to results from the 3D (three-dimensional) radiation hydrodynamics code TROLL, which shows that if continuous tracking of the front position is accessible with this experimental scheme, measurement of its maximum radiation temperature is on the contrary affected by radiation closure of the observation slit. 3D simulations also indicate that this effect can even be worsened if one includes pointing errors of the x-ray imager. Radiation temperature along the tube was then inferred by combining results from the imager to a wall shock breakout time measurement using a velocity interferometer system for any reflector and results from a broadband x-ray spectrometer used to determine the temperature at the exit of the tube. A decrease in the radiation temperature along the tube is observed, the decrease being more important for the higher SiO2 aerogel density.

Implosion experiments of an inertial confinement fusion (ICF) target on the laser megajoule (LMJ) and the National Ignition Facility require, for certain designs, a precise timing coalescence of fo...

The advent of high-power lasers facilities such as the National Ignition Facility (NIF), and Laser Megajoule (LMJ) in the near future opens a new era in the field of High Energy Density Laboratory Astrophysics. The LMJ, keystone of the French Simulation Program, is under construction at CEA/CESTA and will deliver 1.5 MJ with 176 beamlines. The first physics experiments on LMJ will be performed at the end of 2014 with 2 quadruplets (8 beams). The operational capabilities (number of beams and plasma diagnostics) will increase gradually during the following years. We describe the current status of the LMJ facility and the first set of diagnostics to be used during the commissioning phase and the first experiments. The PETAL project (PETawatt Aquitaine Laser), part of the CEA opening policy, consists in the addition of one short-pulse (500 fs to 10 ps) ultra-high-power, high-energy beam (a few kJ compressed energy) to the LMJ facility. PETAL is focalized into the LMJ target chamber and could be used alone or in combination with LMJ beams. In the later case, PETAL will offer a combination of a very high intensity multi-petawatt beam, synchronized with the nanosecond beams of the LMJ. PETAL, which is devoted to the academic research, will also extend the LMJ diagnostic capabilities. Specific diagnostics adapted to PETAL capacities are being fabricated in order to characterize particles and radiation yields that can be created by PETAL. A first set of diagnostics will measure the particles (protons/ions/electrons) spectrum (0.1–200 MeV range) and will also provide point projection proton-radiography capability. LMJ/PETAL, like previously the LIL laser [X. Julien et al., Proc. SPIE 7916 (2011) 791610], will be open to the academic community. Laboratory astrophysics experiments have already been performed on the LIL facility, as for example radiative shock experiments and planetary interiors equation of state measurements.

Since the first experimental campaign conducted in 2014 with mid field Gated X-ray Imager (GXI) and two quadruplets (20 kJ at 351 nm) focused on target, the Laser MegaJoule (LMJ) operational capability is still growing up. New plasma diagnostics have been implemented: a large field 2D GXI, two broadband x-ray spectrometers (called DMX and miniDMX), a specific soft x-ray spectrometer and a Laser Entrance Hole (LEH) imaging diagnostic. A series of experiments have been performed leading to more than 60 shots on target. We will present the plasma diagnostics development status conducted at CEA for experimental purpose. Several diagnostics are now under manufacturing or development which include a Streaked Soft X-ray Imager (SSXI), an Equation Of State (EOS) diagnostic suite (“EOS pack”), a Full Aperture BackScattering (FABS) diagnostic, a Near Backscattered Imager (NBI), a high resolution 2D GXI, a high resolution x-ray spectrometer, a specific set of two polar hard x-ray imagers for LEH characterization and a set of Neutron Time of Flight (NTOF) detectors. We describe here the diagnostics design and performances in terms of spatial, temporal and spectral resolutions. Their designs have taken into account the harsh environment (neutron yields, gamma rays, electromagnetic perturbations, debris and shrapnel) and the safety requirements.

A Velocity Interferometer for Any Reflector (VISAR) [1, 2] and a Streaked Optical Pyrometer (SOP) [3] were implemented on the “Ligne integration Laser” (LIL) facility. Spatial resolution as good as 10 μm in the target plane and velocity resolution as good as 0.1 km/s can be achieved. Several campaigns were performed in 2010 involving various experimental setups and physical processes: Boron EOS, Pre-compress H2 with special setup of diamond anvil cell and Shock coalescence. This feedback will be of a great help for the Laser Megajoule facility (LMJ) VISAR design.

We use the LIL (Ligne d'Integration Laser ) facility to study the coalescence of two planar shocks in an indirectly-driven planar sample of polystyrene. This experiment represents the preliminary stage of the future shock-timing campaign for the Laser Megajoule (LMJ). The main objectives are to validate the experimental concept and to test the numerical simulations. We used a gold spherical hohlraum to convert into X-ray the 351 nm wavelength laser pulse and to initiate the two shocks in the sample. To access time resolved shock velocities and temperature, we used two rear-side diagnostics: a VISAR (Velocity Interferometer System for Any Reflection) working at two different wavelengths and a streaked optical self-emission diagnostic. We observed the coalesced shock, in good agreement with the numerical simulations. We also observed a loss of signal during the first nanoseconds probably due to sample heating from the hohlraum X-ray flux.

International audience; CMOS image sensors (CIS) are promising candidates as part of optical imagers for the plasma diagnostics devoted to the study of fusion by inertial confinement. However, the harsh radiative environment of Megajoule Class Lasers threatens the performances of these optical sensors. In this paper, the vulnerability of CIS to the transient and mixed pulsed radiation environment associated with such facilities is investigated during an experiment at the OMEGA facility at the Laboratory for Laser Energetics (LLE), Rochester, NY, USA. The transient and permanent effects of the 14 MeV neutron pulse on CIS are presented. The behavior of the tested CIS shows that active pixel sensors (APS) exhibit a better hardness to this harsh environment than a CCD. A first order extrapolation of the reported results to the higher level of radiation expected for Megajoule Class Laser facilities (Laser Megajoule in France or National Ignition Facility in the USA) shows that temporarily saturated pixels due to transient neutron-induced single event effects will be the major issue for the development of radiation-tolerant plasma diagnostic instruments whereas the permanent degradation of the CIS related to displacement damage or total ionizing dose effects could be reduced by applying well known mitigation techniques.

The large fluence of 14-MeV neutrons produced in high-yield inertial confinement fusion (ICF) experiments creates a variety of backgrounds in x-ray imagers viewing the implosion. Secondary charged particles produce background light by Cherenkov emission, phosphor screen excitation and possibly scintillation in the optical components of the imager. In addition, radiation induced optical absorption may lead to attenuation of the signal. Noise is also produced directly in the image recorder itself (CCD or film) via energy deposition by electrons and heavy charged particles such as protons and alphas. We will present results from CCD background measurements and compare them to Monte Carlo calculations. In addition we show measurements of luminescence and long-term darkening for some of the glasses employed in imagers.

X-ray imaging instruments will operate in a harsh ionizing radiation background environment on implosion experiments at the National Ignition Facility. These backgrounds consist of mostly neutrons and gamma rays produced by inelastic scattering of neutrons. Imaging systems based on x-ray framing cameras with film and CCD's have been designed to operate in such harsh neutron-induced background environments. Some imaging components were placed inside a shielded enclosure that reduced exposures to neutrons and gamma rays. Modeling of the signal and noise of the x-ray imaging system is presented.

Electron beams generated by laser plasma interaction are applied to several applications. We have chosen two representative applications which emphasize the importance of this electron source, one is the use of this energetic electron beam for treatment planning of tumors, and other is the high resolution /spl gamma/-ray radiography of dense objects. Monte-Carlo simulation is also presented.

An electron beam from a laser-plasma accelerator is converted into a $\ensuremath{\gamma}$-ray source using bremsstrahlung radiation in a dense material. The $\ensuremath{\gamma}$-ray beam has a pointlike source size because it is generated by a high quality electron beam with a small source size and a low divergence. Using this $\ensuremath{\gamma}$-ray source, the radiography of complex and dense objects with submillimeter resolution is performed. It is the first evidence of a $\ensuremath{\gamma}$-ray source size of a few hundreds micrometers produced with laser-driven accelerators. This size is consistent with results from Monte Carlo simulations.

Multilayer mirrors with enhanced bandwidth were developed with special performances for dense plasma diagnostics and mainly for high spatial resolution x-ray imaging. The multilayer coatings are designed to provide broadband x-ray reflectance at low grazing incidence angles. They are deposited onto toroidal mirror substrates. Our research is directed at the development of non-periodic (depth graded) W∕Si multilayer specifically designed for use in the 1 to 30 keV photon energy band. First, we present a study for a 5 to 22 keV x-ray spectral window at 0.45° grazing angle. The goal is to obtain a high and constant reflectivity. Second, we have modeled a broadband mirror coating for harder x-rays in the range from 10 to 30 keV, with a non-periodic structure containing 300 W∕SiC layers with periods in the range from 0.8 to 4 nm, designed for 0.35° grazing incidence angle.

An experiment carried out on the LIL facility is presented. The experiment was designed to investigate the propagation of a multi-kJ laser beam through a plasma produced by the irradiation of a low-density plastic foam. Laser beam self-smoothing has been observed and its consequences on laser imprint and Stimulated Brillouin Scattering (SBS) are discussed.

We present an overview of recent experiments fielded on the LIL facility. A key issue for mega-joule class laser facilities is shrapnel fragment generation. A specific collector was therefore developed to capture debris in aerogel and dedicated shots were done to quantitatively evaluate target fragmentation phenomena. The LIL panel of transmitted and backscattered light diagnostics is well suited for laser-plasma interaction (LPI) experiments. This include gas-filled hohlraum configurations relevant to Indirect Drive ignition targets in order to test the specific LMJ longitudinal SSD technique, as well as LPI experiments with foam targets for laser beam smoothing in underdense plasma in the context of Direct Drive. After Visar commissioning a campaign was dedicated to boron Equation of State (EOS).

The Ligne d'Integration Laser (LIL) facility has been designed as a prototype for the Laser MegaJoule (LMJ) which is a cornerstone of the French 'Simulation Program'. This laser has been intensively used to test and improve the LMJ components. In addition, a large panel of plasma diagnostics has been installed and is currently used to perform laser–plasma experiments. After a brief discussion about the LIL design, we present the last results in various plasma physics domains.