Nicolas Grandjouan

Compression of a cylindrical hydrogen sample driven by an intense co-axial heavy ion beam

The compression of a cryogenic hydrogen cylindrical sample contained in a hollow gold target driven by an intense co-axial uranium beam has been studied. The ion distribution is assumed to be Gaussian in space and parabolic in time. Thehydrodynamicsofthetargetisanalyzedbymeansofone-andtwo-dimensionalnumericalsimulations.Aparametric study is performed to achieve the maximum average hydrogen density and temperature as a function of the sample radius, total number of ions and spread of the spatial ion distribution.Awindow in the beam-target parameters for which hydrogen compression is higher than a factor of 10 and temperature is below 0.2 eV has been found by considering a single bunch that contains 2 10 11 uranium ions delivered in 100 ns. In this range of high densities and low

Target heating in high-energy-density matter experiments at the proposed GSI FAIR facility: Non-linear bunch rotation in SIS100 and optimization of spot size and pulse length

The Gesellschaft fur Schwerionenforschung ~GSI! Darmstadt has been approved to build a new powerful facility named FAIR ~Facility for Antiprotons and Ion Research! which involves the construction of a new synchrotron ring SIS100. In this paper, we will report on the results of a parameter study that has been carried out to estimate the minimum pulse lengths and the maximum peak powers achievable, using bunch rotation RF gymnastic-including nonlinearities of the RF gap voltage in SIS100, using a longitudinal dynamics particle in cell ~PIC! code, ESME. These calculations have shown that a pulse length of the order of 20 ns may be possible when no prebunching is performed while the pulse length gradually increases with the prebunching voltage. Three different cases, including 0.4 GeV0 u, 1G eV 0u, and 2.7 GeV0u are considered for the particle energy. The worst case is for the kinetic energy of 0.4 GeV0u which leads to a pulse length of about 100 ns for a prebunching voltage of 100 kV ~RF amplitude!. The peak power was found to have a maximum, however, at 0.5‐1.5kV prebunching voltage, depending on the mean kinetic energy of the ions. It is expected that the SIS100 will deliver a beam with an intensity of 1‐2 3 10 12 ions. Availability of such a powerful beam will make it possible to study the properties of high-energy-density ~HED! matter in a parameter range that is very difficult to access by other means. These studies involve irradiation of high density targets by the ion beam for which optimization of the target heating is the key problem. The temperature to which a target can be heated depends on the power that is deposited in the material by the projectile ions. The optimization of the power, however, depends on the interplay of various parameters including beam intensity, beam spot area, and duration of the ion bunch. The purpose of this paper is to determine a set of the above parameters that would lead to an optimized target heating by the future SIS100 beam.

A laser experiment for studying radiative shocks in astrophysics

In this article, we present a laboratory astrophysics experiment on radiative shocks and its interpretation using simple modelization.The experiment is performed with a 100-J laser ~pulse duration of about 0.5 ns! which irradiates a 1-mm 3 xenon gas-filled cell. Descriptions of both the experiment and the associated diagnostics are given. The apparition of a radiationprecursorintheunshockedmaterialisevidencedfrominterferometrydiagrams.Amodelincludingself-similar solutions and numerical ones is derived and fairly good agreements are obtained between the theoretical and the experimental results.

Preheating study by reflectivity measurements in laser-driven shocks

A study on preheating effects in laser-driven shock waves is presented. Two different diagnostics were used: the color temperature measurement deduced by recording the target rear side emissivity in two spectral bands, and the rear surface reflectivity measurement by using a probe beam. In order to test the response of the two diagnostics to the preheating, three types of targets characterized by different radiative properties were used. The greater sensitivity of the second diagnostic compared with the first was demonstrated. A model which calculates the reflectivity using a one-dimensional hydrodynamic code data was developed. In this model, the wave propagation equations in the expanding plasma using an appropriate model for the electron–ion collision frequency applicable to the cold solid-hot plasma transition were solved. The comparison between the calculated and measured reflectivities allows us to estimate the preheating process.

Numerical analysis of a multilayered cylindrical target compression driven by a rotating intense heavy ion beam

Numerical analysis of the compression of a cylindrical cryogenic hydrogen sample surrounded by a high-density metallic shell driven by a heavy ion beam has been performed. The beam power profile is assumed to be parabolic in time and Gaussian in space and is made of uranium ions with a kinetic energy of 2.7 GeV0u. The beam center is positioned off axis and rotates around the target axis to provide a uniform annular energy deposition area. An acceptable symmetry in pressure is achieved if the number of revolutions is equal to or larger than 10. The maximum density and pressure of the hydrogen sample is studied as a function of the spread of the beam power Gaussian distribution and the rotation radius. This configuration leads to compressions of the order of 10 and a temperature of a few thousand Kelvin in hydrogen.

Equation of state data experiments for plastic foams using smoothed laser beams

The importance of foams in laser produced plasmas has been recently pointed out in both Inertial Confinement Fusion (ICF) and astrophysics laboratory dedicated experiments. In this paper, Equation of State (EOS) data measurements of plastic porous materials have been experimentally determined using ns laser pulses smoothed with Phase Zone Plates (PZP). Foams of density in the range 20–400 mg/cm3 and thickness about 20 μm were used. A new original scheme for the targets has been designed which allowed, for the first time with laser, EOS data to be obtained for pressures ranging from 0.1 to 2.5 Mbars. Results are discussed and compared with available models.

Optical smoothing for shock-wave generation: Application to the measurement of equations of state

Experimental results are presented on shock-wave generation in solid samples, irradiated directly by optically smoothed laser beams. Random phase plates and phased zone plates have been successfully used. In particular, the last technique allowed the production of uniform shock fronts that have been used for equation of state experiments at pressures above 10 Mbar. Pressures higher than 35 Mbar were achieved in gold, by using laser pulses with energy E = 100 J, and structured, two-step, two-material targets.

Laser driven shock wave acceleration experiments using plastic foams

In this letter, we present an experimental study of shock propagation in a decreasing density gradient which is a common feature in many astrophysical objects. An original scheme for the targets has been designed to investigate the case of a discrete density step. Using foams in a wide density range (20–400 mg/cm−3), we obtained accurate data on shock acceleration at the solid-foam interface. Results are discussed and compared with models.

Dynamics of laser produced shocks in foam–solid targets

The influence of foams on laser shocks was studied with ns laser pulses smoothed with phase zone plates and focused onto layered foam–aluminum targets. Foams of 5–200 mg/cm3 density and 60 μm thickness were used. A strong pressure increase was measured with the foam in comparison to focusing the beam directly onto aluminum due to impedance mismatch at the aluminum–foam interface. Below a particular density, the measured pressure decreased as a result of hydrodynamics effects. Results are compared with computer simulations.

EOS Data Experiments for Plastic Foams Using Smoothed Laser Beams

The importance of foams on laser-produced plasmas has been recently pointed out. In this paper EOS measurements of plastic porous materials have been experimentally determined using ns laser pulses smoothed with phase zone plates. Foams of density in the range 50-200 mg cm-3 and thickness about 20 microns were used. An original scheme for the targets has been designed which allowed us to obtain, for the first time, EOS data for pressures between 0.2-0.8 Mbar. Results are discussed and compared with EOS models.