[en] Some advantages of using matrix methods in optical model are pointed out in connection with evaluation problems and microscopic aspects

[en] The R matrix computable method was used to establish computer codes with optical models, in which the non-local potential is introduced in terms of its matrix elements on the basis of harmonic oscillator states. The study of 'folding' and Hartree-Fock like potentials was thus undertaken

[en] Interaction of light ions beams with various targets is calculated from an ion energy deposition model coupled with an hydrodynamic code, taking account of the plasma evolution during the target heating. The calculations are made in two cases: at low power densities available on a laboratory machine as SIDONIX, at high power densities required for pellet fusion. In the case of low power densities the requirements of a neutron target implosion experiment are discussed. The simulation of deposition processes at high power densities shows that the energy deposition characteristics are strongly modified during the target heating

[en] A major difficulty in the relativistic electron beam (REB) inertial confinement approach is the low REB-target coupling resulting from long electron range in the matter. The beam stagnation mechanism, induced in a thin target by macroscopic electric and magnetic fields, can appreciably enhance this coupling. The chapter 2 of the rapport contributes to the theoretical study of this effect. Models and numerical programs are described, which permit to establish the characteristics of this mechanism and evaluate the role of the various parameters. These models were used to interpret thin foils heating experiments performed on CHANTECLAIR generator at the Centre of Valduc. The orientation of particle research to the light ions beams (LIB) has to led to an intensive study of ions-matter interaction. DEPION model described in chapter 3 of the report provides an evaluation of energy deposition characteristics for any ion incident upon a target, taking into account their evolution during the plasma heating phase

[en] The aim of this report is to find, with a fair accuracy, a proper value λ_mn(c) for the spheroidal differential equation: d/dz[(1-z²)du/dz]+[ λ - c²z² - m²/(1-z²)]u = 0 obtained by the separation of the three variables of the wave equation: Δ²u + k²u = 0 with rotational elongated or flattened ellipsoidal coordinates. The program drawn up calculates λ_mn(c) for any values of (mnc) chosen in the zones 0 ≤ | m | ≤ 10, a whole number; |m| ≤ n ≤ 20, n a whole number; 0 ≤ |c | ≤ 30; previous work has covered a smaller field of values. The function to be solved by the approximation method of the Newton-Raphson type, and the initial value, are chosen so as to converge towards the required solution. (author)

[en] Some advantages of using matrix methods in optical model are pointed out in connection with evaluation problems and microscopic aspects. (author)

[en] High gain target design is based on simple models giving the relations between the laser characteristics (energy, power and pulse shape), the target dimensions and the achievable thermonuclear gain. The DT burning is described by a modified hot spot model, and pellet implosion by the so-called rocket-model. The cavity temperature is given as a function of laser and hohlraum parameters. In the description of the acceleration phase, parameters have been included which characterize the hydrodynamical stability of the imploded capsule (in-flight aspect ratio and convergence ratio). Complex problems occurring with high gain targets, dealing especially with implosion symmetry, are studied with 2D numerical simulations. The influence of parameters such as fuel entropy, capsule in-flight aspect ratio or hohlraum aspect ratio on target gain is stressed. It is shown that, for realistic values of these parameters, a gain of the order of 10 can be achieved with about 2 MJ laser energy at 0.35 μm wavelength. (authors). 6 refs., 11 figs., 1 tab

[en] This chapter examines the experimental results of the implosion of very high aspect ratio microballoons partly consistent with 1-D numerical simulations using a rigorous analytical treatment of the phase of linear instability associated with some phenomenological models describing ''extreme'' types of behavior of thermal effects. The CAMELIA experiments were performed using the 8-beam, 1.06 μm OCTAL laser system. Topics covered include analysis of a particular targets, investigations of hydrodynamic instabilities, numerical modeling of linear perturbations, the irradiation pattern of the OCTAL laser, instabilities induced by non-uniform laser irradiation, and instabilities induced by target defects. It is concluded that a small amount of suprathermal preheating efficiency protects the imploding shell against break-up; the classical Rayleigh-Taylor instability is not critical for type of target/long pulse combination; and implosion uniform is notably improved by acoustic smoothing, but remains highly sensitive to large scale illumination defects, because of the instability of a converging shock to low-order harmonic modes, which can strongly affect the final uniformity of the target core. Includes 2 spherical maps

[en] For the Inertial Confinement Fusion, the different problems to be studied are: DT burning, shell implosion and hydrodynamic instabilities, spherical symmetry of the shell given by the X-rays produced in a hohlraum and laser-plasma interaction. One of the requirements is that the shell stay essentially spherical up to the end of the implosion. In these conditions, 2-D simulations show a gain of 10 in a realistic configuration. The Rayleigh-Taylor instabilities occurring during the shell implosion grow first in the linear regime for which we have some models and experimental results. But the saturation mechanism reduces the final amplitude significantly. By using a simple but global model, we determine an operating domain of the LMJ, taking into account a 25% margin for laser energy. (author)

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