42 research outputs found
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Control of laser plasma instabilities in hohlraums
Laser plasma instabilities are an important constraint on the operating regime for inertial fusion. Many techniques have been developed to control the various laser-driven instabilities. Experiments with long scale length plasmas are testing these instability levels, the nonlinear regimes, and the control mechanisms
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Interaction of plasmas with intense lasers
The interaction of plasmas with intense lasers is an excellent example of how different fields of
physics are inter-connected. Invention of the laser and its ongoing development has allowed the
creation and study of high temperature, dense matter in the laboratory. The results both advance
the underlying plasma science and are relevant to many fields ranging from astrophysics to fusion
and nonlinear physics. A brief overview of the interaction physics is given. Selected topics are
discussed to illustrate the exciting progress in experimental, theoretical and computational
investigations with focussed laser intensities up to 10(21) W/cm(2)
Simulating Poynting Flux Acceleration in the Laboratory with Colliding Laser Pulses
We review recent PIC simulation results which show that double-sided
irradiation of a thin over-dense plasma slab with ultra-intense laser pulses
from both sides can lead to sustained comoving Poynting flux acceleration of
electrons to energies much higher than the conventional ponderomotive limit.
The result is a robust power-law electron momentum spectrum similar to
astrophysical sources. We discuss future ultra-intense laser experiments that
may be used to simulate astrophysical particle acceleration.Comment: Paper accepted for publication in the Astrophysics and Space Science,
Volume for HEDLA06 conference proceedings, edited by G. Kyrala, in pres
Nonintegrable Interaction of Ion-Acoustic and Electromagnetic Waves in a Plasma
In this paper we re-examine the one-dimensional interaction of
electromagnetic and ion acoustic waves in a plasma. Our model is similar to one
solved by Rao et al. (Phys. Fluids, vol. 26, 2488 (1983)) under a number of
analytical approximations. Here we perform a numerical investigation to examine
the stability of the model. We find that for slightly over dense plasmas, the
propagation of stable solitary modes can occur in an adiabatic regime where the
ion acoustic electric field potential is enslaved to the electromagnetic field
of a laser. But if the laser intensity or plasma density increases or the laser
frequency decreases, the adiabatic regime loses stability via a transition to
chaos. New asymptotic states are attained when the adiabatic regime no longer
exists. In these new states, the plasma becomes rarefied, and the laser field
tends to behave like a vacuum field.Comment: 19 pages, REVTeX, 6 ps figures, accepted for publication in Phys.
Rev.
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Laser plasma interactions in hohlraums
Lasers plasma instabilities are an important constraint in x-ray driven inertial confinement fusion. In hohlraums irradiated with 1.06 {mu}m light on the Shiva laser, plasma instabilities were extremely deleterious, driving the program to the use of shorter wavelength light. Excellent coupling has been achieved in hohlraums driven with 0.35 {mu}m light on the Nova laser. Considerable attention is being given to the scaling of this excellent coupling to the larger hohlraums for an ignition target. Various instability control mechanisms such as large plasma wave damping and laser beam incoherence are discussed, as well as scaling experiments to check the instability levels
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Laser-driven instabilities in long scalelength plasmas
In this update lecture we focus on laser-driven instabilities in long scalelength underdense plasmas. Particular attention is given to some recent experiments on Raman scattering of intense laser light. Many important features are in accord with theoretical expectations. These features include a correlation of hot electron generation with Raman scattering, an increase in this scattering as the density scale length increases, and collisional suppression of the instability. Some challenging aspects of the growing data base as well as various deficiencies in the understanding are discussed. The role of the plasmon decay instability 2..omega../sub pe/, Brillouin, and filamentation instabilities is also briefly considered
Laser-plasma coupling
The following topics are discribed: (1) ionization of target, (2) electromagnetic wave propagation in plasma, (3) collisional absorption, (4) light absorption in collisionless plasma, (5) resonance absorption, (6) instabilities, (7) Brillowin instability, and (8) some other effects. (MO
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Wavelength scaling of laser plasma coupling
The use of shorter wavelength laser light both enhances collisional absorption and reduces deleterious collective plasma effects. Coupling processes which can be important in reactor-size targets are briefly reviewed. Simple estimates are presented for the intensity-wavelength regime in which collisional absorption is high and collective effects are minimized