[en] In this paper, we study the interaction of a long moderate electromagnetic pulse with a plasma and, particularly, the interaction of a microwave pulse with low pressure self-generated air plasma under breakdown conditions. A fluid model is coupled to Maxwell equations to describe this interaction. Fluid equations parameters as electron density, drift velocity and electron energy under the influence of laser pulse electric field. The resolution method is restricted to narrow spectrum pulses when the E.M. signal can be considered as an harmonic plane wave. In this case, Maxwell equations are reduced to spatial dependent Helmholtz equation which is solved in an homogeneous and quasi stationary spatial gradient of electronic field inside and outside the inhomogeneous slowly evolving plasma. Finally, we obtain, by Fourier transform, the evolution of the spectrum of reflected and transmitted pulses compared to the incident pulse spectrum. (author)

[en] An original hybrid computational method to solve the 2-D problem of the scattering of an axisymmetric laser beam by an arbitrary-shaped inhomogeneous body of revolution is presented. This method relies on a domain decomposition of the scattering zone into concentric spherical radially homogeneous sub-domains and on an expansion of the angular dependence of the fields on the Legendre polynomials. Numerical results for the fields obtained for various scatterers geometries are presented and analyzed. (authors)

[en] Soft x-ray gain has been demonstrated at 5.03 nm within a laser produced plasma of Ni-like ytterbium. Experiments will also be described with higher Z Ni-like ions which can produce even shorter wavelength x-ray laser transition. 3 refs

[en] We have studied the absorption of aluminium X-ray lines through a gold plasma by focusing a high intensity laser-beam onto a specific target. Absorption in the wavelength range of 5 to 7 A has been evidenced and measured for Aluminium resonance lines

[en] Numerical simulations are used to study acceleration of protons by intense laser pulses and the induced heating of a secondary target using this proton beam. Laser-plasma interaction and ion acceleration are modeled with a multidimensional, relativistic particle-in-cell code. Proton slowing-down and secondary target heating are computed with a two-dimensional Monte Carlo and a one-dimensional Lagrangian hydrodynamics codes. Strategies for optimization of heating uniformity include tailoring the accelerated proton spectrum with specific target geometries or laser pulse parameters. A trade-off must then be found between heating uniformity and efficiency. The parameters (temperature, depth and radius of heated zone, characteristic heating and hydrodynamics times) that could be obtained on current short pulse laser facilities, using a typical 50 fs Gaussian pulse with an intensity of several 10¹⁹ W/cm², are explored.

[en] A Lagrangian method is introduced for the integration of non-linear Fokker-Planck equations. Examples of exact solutions obtained in this way are given, and also the explicit scheme used for the computation of numerical solutions. The method is, in addition, shown to be of a Lie-admissible type

[en] The idea of a Brownian quasi-particle and the associated differentiable flow (with nonselfadjoint forces) are used here in the context of a stochastic description of the approach towards statistical equilibrium. We show that this quasi-particle flow acquires, at equilibrium, the principal properties of a conservative Hamiltonian flow. Thus the model of Brownian quasi-particles permits us to establish a link between the stochastic description and the Gibbs description of statistical equilibrium

[en] Thin and thick composite targets of various materials (Al, CH, Au) have been irradiated on both circular and linear focal spots with the OCTAL laser facility at wavelengths 1.06 μm and 0.35 μm and laser irradiances 5 10¹² w/cm² to 5 10¹⁴ w/cm². X ray spectra in the range 5 - 8 A and 15 - 300 A recorded respectively by means of flat TlaP and grazing incidence spectrographs gave some experimental evidence of population inversion in aluminum plasma

[en] Shrapnel fragments, produced when target/diagnostic components are impulse loaded, can reduce the lifetime of final optical components. They give simulations results of shrapnel generation in thin metal plates loaded by laser heating. They discuss two approaches to predicting the size and velocity distribution of the shrapnel fragments. The first uses the 2D LASNEX code to calculate energy absorption, shock propagation, and material response. The calculated strain rates combined with hydrodynamic quantities are used to determine properties of the fragments. The second uses the 1D DELPOR code to calculate energy absorption with the results coupled to the 3D HESIONE code to calculate dynamic fragmentation. They show results of varying the incident laser energy and the plate material. They compare with data obtained using low-density aerogel to capture shrapnel fragments

[en] By focussing a powerful laser beam at the 1.053 μm wavelength over a line focus on a germanium target, a significant amplification of X-rays in Ge²²⁺ at two wavelengths has been measured. Numerous spectroscopic devices allowed us to record data interpreted by means of an ionization model providing the plasma characterization