13,675 research outputs found
Three-dimensional simulations of laser-plasma interactions at ultrahigh intensities
Three-dimensional (3D) particle-in-cell (PIC) simulations are used to
investigate the interaction of ultrahigh intensity lasers (
W/cm) with matter at overcritical densities. Intense laser pulses are
shown to penetrate up to relativistic critical density levels and to be
strongly self-focused during this process. The heat flux of the accelerated
electrons is observed to have an annular structure when the laser is tightly
focused, showing that a large fraction of fast electrons is accelerated at an
angle. These results shed light into the multi-dimensional effects present in
laser-plasma interactions of relevance to fast ignition of fusion targets and
laser-driven ion acceleration in plasmas.Comment: 2 pages, 1 figur
Magnetic control of particle-injection in plasma based accelerators
The use of an external transverse magnetic field to trigger and to control
electron self-injection in laser- and particle-beam driven wakefield
accelerators is examined analytically and through full-scale particle-in-cell
simulations. A magnetic field can relax the injection threshold and can be used
to control main output beam features such as charge, energy, and transverse
dynamics in the ion channel associated with the plasma blowout. It is shown
that this mechanism could be studied using state-of-the-art magnetic fields in
next generation plasma accelerator experiments.Comment: 10 pages, 3 figure
A global simulation for laser driven MeV electrons in -diameter fast ignition targets
The results from 2.5-dimensional Particle-in-Cell simulations for the
interaction of a picosecond-long ignition laser pulse with a plasma pellet of
50- diameter and 40 critical density are presented. The high density
pellet is surrounded by an underdense corona and is isolated by a vacuum region
from the simulation box boundary. The laser pulse is shown to filament and
create density channels on the laser-plasma interface. The density channels
increase the laser absorption efficiency and help generate an energetic
electron distribution with a large angular spread. The combined distribution of
the forward-going energetic electrons and the induced return electrons is
marginally unstable to the current filament instability. The ions play an
important role in neutralizing the space charges induced by the the temperature
disparity between different electron groups. No global coalescing of the
current filaments resulted from the instability is observed, consistent with
the observed large angular spread of the energetic electrons.Comment: 9 pages, 6 figures, to appear in Physics of Plasmas (May 2006
The Schwarzschild-de Sitter solution in five-dimensional general relativity briefly revisited
We briefly revisit the Schwarzschild-de Sitter solution in the context of
five-dimensional general relativity. We obtain a class of five-dimensional
solutions of Einstein vacuum field equations into which the four-dimensional
Schwarzschild-de Sitter space can be locally and isometrically embedded. We
show that this class of solutions is well-behaved in the limit of lambda
approaching zero. Applying the same procedure to the de Sitter cosmological
model in five dimensions we obtain a class of embedding spaces which are
similarly well-behaved in this limit. These examples demonstrate that the
presence of a non-zero cosmological constant does not in general impose a rigid
relation between the (3+1) and (4+1)-dimensional spacetimes, with degenerate
limiting behaviour.Comment: 7 page
Beam loading in the nonlinear regime of plasma-based acceleration
A theory that describes how to load negative charge into a nonlinear,
three-dimensional plasma wakefield is presented. In this regime, a laser or an
electron beam blows out the plasma electrons and creates a nearly spherical ion
channel, which is modified by the presence of the beam load. Analytical
solutions for the fields and the shape of the ion channel are derived. It is
shown that very high beam-loading efficiency can be achieved, while the energy
spread of the bunch is conserved. The theoretical results are verified with the
Particle-In-Cell code OSIRIS.Comment: 5 pages, 2 figures, to appear in Physical Review Letter
Jalo MG-65 - Common bean cultivar.
Jalo MG-65 is a large-seeded common bean cultivar with indeterminate growth habit (type III) released for planting in Minas Gerais State. It belongs to the Jalo class (yellow seeds) and has a high yield potential. Usually, it is ready for harvesting within 70-80 days. It is resistant to fusarium with and moderately resistant to rust, angular leaf spot, alternaria leaf spot, and powdery mildew
Riemann-Cartan Space-times of G\"odel Type
A class of Riemann-Cartan G\"odel-type space-times are examined in the light
of the equivalence problem techniques. The conditions for local space-time
homogeneity are derived, generalizing previous works on Riemannian G\"odel-type
space-times. The equivalence of Riemann-Cartan G\"odel-type space-times of this
class is studied. It is shown that they admit a five-dimensional group of
affine-isometries and are characterized by three essential parameters : identical triads () correspond to locally
equivalent manifolds. The algebraic types of the irreducible parts of the
curvature and torsion tensors are also presented.Comment: 24 pages, LaTeX fil
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