The objective of Target Physics Program at CEA is the achievement of ignition on the LMJ, a glass laser facility of 1.8 MJ which will be completed by 2008. They include theoretical work, experimental work and numerical simulations. An important part of experimental studies is made in collaboration with U.S. DOE Laboratories : Lawrence Livermore National Laboratory, Los Alamos National Laboratory and the Laboratory for Laser Energetics at the University of Rochester. Experiments were performed on Phebus, NOVA (LLNL) and OMEGA (LLE); they included diagnostics developments. Recent efforts have been focused on Laser Plasma Interaction, hohlraum energetics, symmetry, ablator physics and hydrodynamic instabilities. Ongoing work prepare the first experiments on the LIL which is a prototype facility of the LMJ (8 of its 240 beams). They will be performed by 2002. Recent progress in ICF target physics allows us to precise laser specifications to achieve ignition with reasonable margin.

The laser program developed at the Centre d'Etudes de Limeil-Valenton, Saint-Georges, France (CEL-V) is concentrated on a systematic investigation of indirect drive fusion; by comparison with direct drive, this process is expected to provide the required irradiation uniformity with relaxed constraints on laser beam quality. The main concerns are radiative transfer and preheat, hydrodynamic instabilities, and high-density X-ray driven implosions. Ablative implosion experiments have been conducted with the two beams at the Phebus facility (5 kJ, 1.3 ns, 0.35 μm). Symmetry was proved to be controlled by the casing structure, following scaling laws describing hohlraum physics. A compressed DT density ∼100 ρ0 (ρ0 liquid DT density) has been deduced from activation measurements. Different aspects of the soft X-ray transfer processes, and particularly of the ablation of a low-Z material, which drives the capsule implosion, are dealt with in detailed investigations. Reported here are results on X-ray reemission and penetration in several materials, and on induced hydrodynamics of accelerated foils. The laser energy required to reach fuel ignition conditions has been evaluated from numerical simulations as well as from analytical models, taking into account hohlraum physics, capsule implosion, hot spot formation, and burn propagation. Several crucial parameters have been drawn, the most important being the radiation temperature. A target gain in the order of 10 appears achievable with a 2-MJ laser.

A fast valve injects gas transiently near the insulator in order to optimize pressures separately for breakdown and beam generation. On a different machine without gas injection the interaction of the ion beam with targets of variable thicknesses can be used to diagnose the beam.

High voltages and powers can be generated by turbulence in current discharges, and then transferred to electron and ion beams. These beams are the cause of large X-ray and neutron emissions, respectively. With a 340 kJ - 40 kV capacitor bank it is measured a deuteron beam of 1.2 MA - 300 keV which interacts with a 30 m diam. deuterated polyethylene target located In the plasma chamber. The experiments have been conducted in a very extended range of energy corresponding to a 100 time increase in the discharge current. With a further increase by a factor 3-10 one would reach the level requested for breakeven in Inertial confinement studies.

The dense plasma focus formed under special conditions at the open end of a coaxial accelerator is considered as a plasma neutron source the versatility of which is still unexplored. The neutron yield in space and time as well as the neutron spectrum are determined by the local parameters of the plasma and the surrounding fusionable gas. The physics governing these parameters together with the diagnostics for measuring these quantities are treated in detail. The engineering problems associated with the creation, compression and heating of the plasma are described in particular. Two different types of energy storage systems, a capacitive one and an inductive one are discussed. As examples two devices already in operation are described in detail: one for particular high neutron yield per discharge (1013 dd-neutrons) and one for high repetition rates (two discharges per second at a yield of 6 × 109 dd-neutrons per discharge). Finally the perspectives for developing the plasma focus as a neutron source with a flux of 14 MeV neutrons beyond 1015 neutrons/cm2·s are discussed.

A systematic experimental study is conducted in order to measure the density and configuration of the plasma by holographic interferometry, and the ion temperature and level of turbulence by cooperative laser scattering. The two measurements are done in various phases of the plasma, before, during, and after the filament breakup. Suprathermal scattering during the filament phase and the successive development of an ionizing wave are evidenced for the first time. The anisotropy of the neutron emission is found to exist in all regimes by the simultaneous measurement of the energy spectra in two directions. A possible explanation of the neutron emission is given. It is concluded that nonthermal processes play an essential role in the plasma focus.

The electron density in plasmas can be measured by interferometry even in glass vessels with poor optical quality if the double exposure holographic technique is used. Thus the density of a non-cylindrical Z-pinch discharge has been obtained as a function of space and time. The initial location of the discharge is assigned by the curved contour of the vessel. Results are compared with two numerical codes; one is one-dimensional MHD and the other is a two- dimensional snowplough.