Fast ignition of fusion targets by laser-driven electrons

We present hybrid PIC simulations of fast electron transport and energy deposition in pre-compressed fusion targets, taking full account of collective magnetic effects and the hydrodynamic response of the background plasma. Results on actual ignition of an imploded fast ignition configuration are shown accounting for the increased beam divergence found in recent experiments [J.S. Green et al., Phys. Rev. Lett. 100, 015003 (2008)] and the reduction of the electron kinetic energy due to profile steepening predicted by advanced PIC simulations [B. Chrisman et al. Phys. Plasmas 15, 056309 (2008)]. Target ignition is studied as a function of injected electron energy, distance of cone-tip to dense core, initial divergence and kinetic energy of the relativistic electron beam. We found that beam collimation reduces substantially the ignition energies of the cone-guided fuel configuration assumed here.Comment: 15 pages, 9 figures. accepted for publication in Plasma Physics and Controlled Fusio

Fast ignition of inertial fusion targets by laser-driven carbon beams

Two-dimensional simulations of ion beam driven fast ignition are presented. Ignition energies of protons with Maxwellian spectrum and carbon ions with quasimonoenergetic and Maxwellian energy distributions are evaluated. The effect of the coronal plasma surrounding the compressed deuterium-tritium is studied for three different fuel density distributions. It is found that quasi- monoenergetic ions have better coupling with the compressed deuterium-tritium and substantially lower ignition energies. Comparison of quasimonoenergetic carbon ions and relativistic electrons as ignitor beams shows similar laser energy requirements, provided that a laser to quasimonoenergetic carbon ion conversion efficiency around 10% can be achieved.Comment: 8 pages, 10 figures, published in Physics of Plasma

Fast ignition driven by quasi-monoenergetic ions: Optimal ion type and reduction of ignition energies with an ion beam array

Fast ignition of inertial fusion targets driven by quasi-monoenergetic ion beams is investigated by means of numerical simulations. Light and intermediate ions such as lithium, carbon, aluminium and vanadium have been considered. Simulations show that the minimum ignition energies of an ideal configuration of compressed Deuterium-Tritium are almost independent on the ion atomic number. However, they are obtained for increasing ion energies, which scale, approximately, as Z^2, where Z is the ion atomic number. Assuming that the ion beam can be focused into 10 {\mu}m spots, a new irradiation scheme is proposed to reduce the ignition energies. The combination of intermediate Z ions, such as 5.5 GeV vanadium, and the new irradiation scheme allows a reduction of the number of ions required for ignition by, roughly, three orders of magnitude when compared with the standard proton fast ignition scheme

Reducing the complexity of a multiview H.264/AVC and HEVC hybrid architecture

With the advent of 3D displays, an efficient encoder is required to compress the video information needed by them. Moreover, for gradual market acceptance of this new technology, it is advisable to offer backward compatibility with existing devices. Thus, a multiview H.264/Advance Video Coding (AVC) and High Efficiency Video Coding (HEVC) hybrid architecture was proposed in the standardization process of HEVC. However, it requires long encoding times due to the use of HEVC. With the aim of tackling this problem, this paper presents an algorithm that reduces the complexity of this hybrid architecture by reducing the encoding complexity of the HEVC views. By using Na < ve-Bayes classifiers, the proposed technique exploits the information gathered in the encoding of the H.264/AVC view to make decisions on the splitting of coding units in HEVC side views. Given the novelty of the proposal, the only similar work found in the literature is an unoptimized version of the algorithm presented here. Experimental results show that the proposed algorithm can achieve a good tradeoff between coding efficiency and complexity

Three-dimensional fast electron transport for ignition-scale inertial fusion capsules

Three-dimensional hybrid PIC simulations are presented to study electron energy transport and deposition in a full-scale fast ignition configuration. Multi-prong core heating close to ignition is found when a few GA, few PW beam is injected. Resistive beam filamentation in the corona seeds the 3D current pattern that penetrates the core. Ohmic heating is important in the low-density corona, while classical Coulomb deposition heats the core. Here highest energy densities (few Tbar at 10 keV) are observed at densities above 200 g/cc. Energy coupling to the core ranges from 20 to 30%; it is enhanced by beam collimation and decreases when raising the beam particle energy from 1.5 to 5.5 MeV.Comment: 5 pages, 5 figure

Enhanced relativistic-electron beam collimation using two consecutive laser pulses

The double laser pulse approach to relativistic electron beam (REB) collimation has been investigated at the LULI-ELFIE facility. In this scheme, the magnetic field generated by the first laser-driven REB is used to guide a second delayed REB. We show how electron beam collimation can be controlled by properly adjusting laser parameters. By changing the ratio of focus size and the delay time between the two pulses we found a maximum of electron beam collimation clearly dependent on the focal spot size ratio of the two laser pulses and related to the magnetic field dynamics. Cu-K alpha and CTR imaging diagnostics were implemented to evaluate the collimation effects on the respectively low energy ( MeV) components of the REB

Notas sobre el género Lepiota (Pers.: Fr.) Gray (Agaricales, Basidiomycotina) en el sudeste español

Se aportan datos corológicos de los 31 txones pertenecientes al género Lepiota (Pers.: Fr.) Gray ss. Kühner (1980) encontrados en el S.E. de la península ibérica. Se propone una nueva combinación: Lepiota subsquarrosa (Locq.) Gea et Honrubia.Notes on the genus Lepiota (Pers.: Fr.) Gray (Agaricales, Basidiomycotina) in South-Fast Spain. Thirty-one taxa of the genus Lepiota (Pers.: Fr.) Gray, sensu Kühner (1980) are recorded. Lepiota subsquarrosa (Locq.) Gea et Honrubia nov. comb. is proposed

Notas sobre el género Lepiota (Pers.: Fr.) Gray (Agaricales, Basidiomycotina) en el sudeste español

Se aportan datos corológicos de los 31 txones pertenecientes al género Lepiota (Pers.: Fr.) Gray ss. Kühner (1980) encontrados en el S.E. de la península ibérica. Se propone una nueva combinación: Lepiota subsquarrosa (Locq.) Gea et Honrubia.Notes on the genus Lepiota (Pers.: Fr.) Gray (Agaricales, Basidiomycotina) in South-Fast Spain. Thirty-one taxa of the genus Lepiota (Pers.: Fr.) Gray, sensu Kühner (1980) are recorded. Lepiota subsquarrosa (Locq.) Gea et Honrubia nov. comb. is proposed