[en] Because of economic and quality securing reasons a constant wall thickness of extruded pipes in circumference and extrusion direction is an important production aim. Therefore a microcomputer controlled system was developed, which controls die centering with electric motors. The control of wall thickness distribution; was realized with two conceptions: a dead time subjected control with a rotating on line wall thickness measuring instrument and an adaptive control with sensors in the pipe die. With a PI-algorithm excentricities of 30% of the wall thickness could be controlled below a trigger level of 2% within three dead times. (orig.)

[en] Shock ignition is an inertial confinement fusion scheme where the ignition conditions are achieved in two steps. First, the DT shell is compressed at a low implosion velocity creating a central core at a low temperature and a high density. Then, a strong spherical converging shock is launched before the fuel stagnation time. It increases the central pressure and ignites the core. It is shown in this paper that this latter phase can be described analytically by using a self-similar solution to the equations of ideal hydrodynamics. A high and uniformly distributed pressure in the hot spot can be created thus providing favorable conditions for ignition. Analytic ignition criteria are obtained that relate the areal density of the compressed core with the shock velocity. The conclusions of the analytical model are confirmed in full hydrodynamic simulations.

[en] CHIC is a code of Lagrangian hydrodynamics and implosion that has been developed since 2003 for the simulation of plasma experiments concerning inertial fusion. The transport of electron energy is assured with the Spitzer-Harm diffusion model with flux limiter. The propagation of the laser beams inside the plasma is computed by an algorithm of 3-dimensional beam launching that takes into account refraction as well as collisional absorption. The self-generated transverse magnetic fields are assessed by a magnetohydrodynamics model that stems from a generalized Ohm's law. The coupling with electron energy transport is assured with Braginskii conduction model. The validation of this code has been performed with various plasma experiments. (A.C.)

[en] This paper deals with ablation front instabilities simulations in the context of direct drive inertial confinement fusion. A simplified deuterium-tritium target, representative of realistic target on LIL (laser integration line at Megajoule laser facility) is considered. We describe here two numerical approaches: the linear perturbation method using the perturbation codes Perle (planar) and Pansy (spherical) and the direct simulation method using our bi-dimensional hydrodynamic code Chic. Our work shows a good behaviour of all methods even for large wavenumbers during the acceleration phase of the ablation front. We also point out a good agreement between model and numerical predictions at ablation front during the shock wave transit

[en] Shock ignition of DT capsules involves two major steps. First, the fuel is assembled by means of a low velocity conventional implosion. At stagnation, the central core has a temperature lower than the one needed for ignition. Then a second, strong spherical converging shock, launched from a high intensity laser spike, arrives to the core. This shock crosses the core, rebounds at the target center and increases the central pressure to the ignition conditions. In this work we consider this latter phase by using the Guderley self-similar solution for converging flows. Our model accounts for the fusion reaction energy deposition, thermal and radiation losses thus describing the basic physics of hot spot ignition. The ignition criterion derived from the analytical model is successfully compared with full scale hydrodynamic simulations. (authors)

[en] In laser produced plasmas large self-generated magnetic fields have been measured. The classical formulas by Braginskii predict that magnetic fields induce a reduction of the magnitude of the heat flux and its rotation through the Righi-Leduc effect. In this paper a second order tensorial diffusion method used to correctly solve the Righi-Leduc effect in multidimensional code is presented

[en] The European High Power laser Energy Research (HiPER) project aims at demonstrating the feasibility of high gain inertial confinement fusion using the fast ignitor approach. A baseline target has been recently developed by Atzeni et al. [Phys. Plasmas 14, 052702 (2007)]. The radiative transport have a minor effect on the peak areal density but decreased by 20% the peak density. We have found that with 95 kJ of absorbed laser energy one can assemble the fuel with a peak density around 500 g/cm³ and a peak areal density of 1.2 g/cm². This implies a total target gain of about 60. (authors)

[en] We present a complete Arbitrary Lagrangian Eulerian (ALE) strategy devoted to the computation of multi-material fluid flows using the volume of fluid (VOF) interface reconstruction method applied to plasma physics and inertial confinement fusion (ICF). The interface tracking is coupled to a two-temperature hydrodynamics model in the framework of a collocated Lagrangian scheme. Some numerical examples, such hot shock tube problem and ICF-like problem, provide a clear evidence of the robustness and the accuracy of the method. (authors)

[en] The European High Power laser Energy Research (HiPER) project aims at demonstrating the feasibility of high gain inertial confinement fusion using the fast ignitor approach. A baseline target has been recently developed by Atzeni et al (2007 Phys. Plasmas 14 052702). We study here the robustness of this target during the compression phase and define pulse shape tolerances for a successful fuel assembly. The comparison between a standard and a relaxation pulse shows that the latter allows one to reduce both the laser power contrast and the growth of perturbations due to Rayleigh-Taylor instability. We have found that with 95 kJ of absorbed laser energy one can assemble the fuel with a peak density around 500 g cm^-2 and a peak areal density of 1.2 g cm^-2. This implies a total target gain of about 60

[en] Hydrodynamics and robustness of three high yield targets within the HiPER project are presented. Using realistic illumination nonuniformity configuration, hydrodynamic perturbations sensitivity analysis is carried out. A rather simple hydrodynamic perturbation modeling sequence is validated thanks to 2D simulations. 1D simulations post-processed with such a modeling sequence provide a good estimation of the thermonuclear burn. First estimates of hydrodynamic safety factor are given.