[en] With the achievement of the chirped pulse amplification technique, laser intensities have been increased by several orders of magnitude, permitting now to reach the relativistic regime (e.g. electrons oscillate in the laser field with relativistic velocities). The interaction of such powerful lasers with underdense plasmas has allowed studies of various new phenomena. In particular, extremely high electric fields, several orders of magnitude greater than those obtained in conventional accelerators, have been measured. These high fields are able to trap plasma background electrons and accelerate them to relativistic energies. As a consequence, relativistic electron beams are now routinely being produced using lasers in the laboratory. A review of the processes involved as well as the evolution of compact laser plasma accelerators will be presented. Some already identified applications of these new particle beams with unique parameters will be also presented. (Author)

No abstract available

[en] Automatic translation: To determine the decay constants of the prompt neutron flux and the absolute power at the ITR, neutron noise measurements were carried out on core configurations I and II. In this way, both α_c and power could be measured quickly (recording time 17 min) and accurately. For Core 1, the decay constant was determined to be α_c = 300 sec^-1 (maximum error: ±5%). The maximum error of the power calibration was ±9%. Thanks largely to improvements in measurement technology, Core II When determining α_c (α = 865 sec^-1 ), the maximum error is kept smaller than ±1% and the maximum error of the power calibration is kept smaller than ±2%. (This does not take into account the form factor, which was subsequently calculated to be 1.053 for Core I and 1.102 for Core II.

[en] This report describes the experiment 'Electron acceleration in a pre-formed plasma at 527 nm.'; carried out at the Central Laser Facility (CLF) from the 5th Jan to the 14th Feb 1998. The experiment, funded by the Framework IV Large Scale Facilities access scheme, was proposed by Dr. F. Amiranoff, LULI, Ecole Polytechnique, France and carried out by visiting researchers from the Laboratory. They were supported by researchers from: Imperial College, London, UK; UCLA, Los Angeles, California, US; University of Orsay, France; and the Central Laser Facility, Rutherford Appleton Laboratory. (author)

No abstract available

[en] Investigations on sorption and diffusion properties of tritium in A3-matrix-graphite were performed in order to evaluate the tritium balance of an HTGR. Laboratory experiments were made with tritium and deuterium serving as a model gas. Graphite samples were heated up to 1000⁰C maximum in an ultra-high vacuum device. Then the gas was injected gradually, while observing the pressure until equilibrium was attained. From these measurements the kinetics and the isotherm of adsorption were derived. After loading the samples with tritium, release measurements were made at different temperatures. They could be evaluated as a desorption process

[en] Complete test of publication follows. The concepts of laser-plasma based accelerator and injector are discussed here. A two stage laser plasma accelerator design study for the production of a high-quality 3 GeV electron beam with low energy spread (1%) is proposed. New results demonstrating colliding laser pulses scheme will be also presented. These laser-produced particle beams have a number of interesting properties and could lend themselves to applications in many fields, including medicine (radiotherapy), chemistry (radiolysis), accelerator physics, and as a source for the production of γ rays beams for non-destructive material inspection by radiography, or for future compact XFEL machines.

[en] The implementation of gas jet targets appears to be a very attractive alternative to pre-exploded thin foils targets for relativistic laser plasma interactions. In this article, we report a review of recent results obtained by focusing a nanosecond laser beam onto a gas jet target. Large scale and quasi-stationary plasmas are then produced, these plasmas have been characterized by Thomson scattering diagnostics over a wide range of temperature (0.5 - 1.3 keV) and density (1*10¹⁹ - 1.6*10²⁰ cm^-3). Because density and velocity gradient are small in comparison with pre-exploded foils, they offer as it is shown here a new approach to study parametric instabilities such as Raman and Brillouin instabilities or Smoothing. The use of high Z gases can be a good benchmark for atomic physics in warm and dense plasmas

[en] The performances of ultra-short and very powerful lasers enable the creation of particle beams with specific and very interesting properties. The electron beams that are produced are ultra-brief (< 100 fs), very collimated (a few degrees), strongly charged (a few nC), energetic (up to 200 MeV) and have a very strong acceleration gradient (from 0 to 200 MeV over 1 mm long distance). The author presents the physics associated to the plasma acceleration with lasers (self-channeling and forced-channeling are described). The ponderomotive force, the plasma wave with its electrical field, and the plasma index are basic notions that are recalled in this article

[en] An experiment investigating the production of relativistic electrons from the interaction of ultrashort multi-terawatt laser pulses with an underdense plasma is presented. Electrons were accelerated to tens of MeV and the maximum electron energy increased as the plasma density decreased. Simulations have been performed in order to model the experiment. They show a good agreement with the trends observed in the experiment and the spectra of accelerated electrons could be reproduced successfully. The simulations have been used to study the relative contribution of the different acceleration mechanisms: plasma wave acceleration, direct laser acceleration and stochastic heating. The results show that in low density case (1 percent of the critical density) acceleration by laser is dominant mechanism. The simulations at high density also suggest that direct laser acceleration is more efficient that stochastic heating