[en] We report experimental measurements of the equation of state of water with laser-driven shock waves. The water samples are pre-compressed using diamond anvil cells to initial pressures ranging from 1 to 6 kbar. The shock is formed into a flat, 100 μm thick diamond and transmitted into a 25 μm thick quartz plate, which we use as a reference material for impedance mismatch. Two VISAR interferometric diagnostics allow the measurement of the shock velocity into both quartz and water. The light emitted by the sample is collected in the wavelength range 600 ± 12.5 nm, and imaged onto a calibrated streak camera, which measures the equivalent black body temperature of the shocked sample. A few points were obtained, five of which show reliable measurements of pressure, density and temperature of water. The results agree with the Sesame tables when taking into account experimental uncertainties. (authors)

[en] The knowledge of the equations of state of helium and hydrogen in high temperature and high density ranges is necessary to design inertial fusion targets adequately. The experimental assessment of the relationship that links volume, pressure, energy, temperature and ionization in this thermodynamic domain is a real challenge. We have developed a new technique that combines static compression and dynamical compression. It is based on the generation of laser shocks in diamond anvil cells. This paper illustrates the application of the method to helium via the warm dense matter (WDM) technique that is well adapted to highly compressible fluids. It appears that the WDM technique needs to be refined. (A.C.)

[en] 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. (authors)

[en] 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. (authors)

[en] Laser-driven inertial confinement fusion relies on the implosion of a capsule whose conditioning is made by successive shocks that compress it. These shocks must occur at a certain depth of the capsule and within a time range of a hundred picoseconds in order to wield an optimal implosion. The presence of carbon in the capsule is the cause of a supplementary shock called photoabsorption shock. This shock was predicted theoretically and has been recently observed in an experiment performed on the LIL laser facility.

[en] We summarize current methods and results for coupling laser-induced shocks into pre-compressed Helium contained in a diamond anvil cell (DAC). We are able to load helium, hydrogen, deuterium, and helium-hydrogen mixtures into a DAC and propagate a laser-generated shock into the pre-compressed sample. This technique has allowed us to measure the Hugoniot for helium at initial densities ranging from 1 to 3.5 times liquid density. We have developed and used a methodology whereby all of our measurements are referenced to crystalline quartz, which allows us to update our results as the properties of quartz are refined in the future. We also report the identification and elimination of severe electro-magnetic pulses (EMP) associated with plasma stagnation associated with ablation in a DAC.

[en] 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).

[en] The experiments in which matter is compressed through power laser requires probe techniques able to measure the atomic structure in very short times. An X-ray diffractometer has been specially designed for the LULI2000 laser. One of the two laser beams is used to compress matter while the other one is used to generate X-rays. The main challenge lays in the ability of the diffractometer to tell the diffracted signal given by the compressed material from the intense background noise. A shielded box surrounding the sample to be compressed has been designed. 5 inside sides of the box are covered with X-ray detectors and on one side an aperture allows X-rays to irradiate the front side of the sample while the back side of the sample is compressed by the laser radiation. Combined with a pressure probe, this device has allowed the study of the evolution of the atomic structure of an iron sample beyond 200 GPa pressure. (A.C.)

[en] We performed an experiment on the 'Ligne d'Integration Laser' facility to produce strong shocks with plasma conditions relevant for the Shock Ignition approach to Inertial Confinement Fusion. Two kinds of targets have been used: planar and hemispherical. We observe an increase in the shock velocity in hemispherical geometry, which entails a fairly planar shock despite the Gaussian focal spot. Numerical results reproduce the shock dynamics in the two cases in a successful way, indicating, for laser intensities around 1.5 x 10¹⁵ W/cm² at 3 omega, an ablation pressure of (90±20) Mbar and (120±20) Mbar in planar and hemispherical geometry, respectively. (authors)

[en] An experiment performed at the National Ignition Facility (Livermore - USA) has allowed the compression of deuterium up to 6 Mbar through a perfectly controlled dynamic process. Deuterium was contained in the space between a copper sliding ram and a LiF window that has allowed the observation of the transition through an optical diagnostic. The 168 laser beams of NIF have been specifically tuned and focused on the piston to rise the pressure up to 6 Mbar. The quick and important rise of the reflectivity has clearly set the transition to metallic deuterium at 2 Mbar for temperatures below 2000 K. (A.C.)