2,180 research outputs found
Proton acceleration by circularly polarized traveling electromagnetic wave
The acceleration of charged particles, producing collimated mono-energetic
beams, over short distances holds the promise to offer new tools in medicine
and diagnostics. Here, we consider a possible mechanism for accelerating
protons to high energies by using a phase-modulated circularly polarized
electromagnetic wave propagating along a constant magnetic field. It is
observed that a plane wave with dimensionless amplitude of 0.1 is capable to
accelerate a 1 KeV proton to 386 MeV under optimum conditions. Finally we
discuss possible limitations of the acceleration scheme.Comment: 6 pages, 9 figure
Prospects and limitations of wakefield acceleration in solids
Advances in the generation of relativistic intensity pulses with wavelengths
in the X-ray regime, through high harmonic generation from near-critical
plasmas, opens up the possibility of X-ray driven wakefield acceleration. The
similarity scaling laws for laser plasma interaction suggest that X-rays can
drive wakefields in solid materials providing TeV/cm gradients, resulting in
electron and photon beams of extremely short duration. However, the wavelength
reduction enhances the quantum parameter , hence opening the question of
the role of non-scalable physics, e.g., the effects of radiation reaction.
Using three dimensional Particle-In-Cell simulations incorporating QED effects,
we show that for the wavelength nm and relativistic amplitudes
-100, similarity scaling holds to a high degree, combined with
operation already at moderate , leading to photon
emissions with energies comparable to the electron energies. Contrasting to the
generation of photons with high energies, the reduced frequency of photon
emission at X-ray wavelengths (compared to at optical wavelengths) leads to a
reduction of the amount of energy that is removed from the electron population
through radiation reaction. Furthermore, as the emission frequency approaches
the laser frequency, the importance of radiation reaction trapping as a
depletion mechanism is reduced, compared to at optical wavelengths for
leading to similar .Comment: 9 pages, 7 figure
Localized whistlers in magnetized spin quantum plasmas
The nonlinear propagation of electromagnetic (EM) electron-cyclotron waves
(whistlers) along an external magnetic field, and their modulation by
electrostatic small but finite amplitude ion-acoustic density perturbations are
investigated in a uniform quantum plasma with intrinsic spin of electrons. The
effects of the quantum force associated with the Bohm potential and the
combined effects of the classical as well as the spin-induced ponderomotive
forces (CPF and SPF respectively) are taken into consideration. The latter
modify the local plasma density in a self-consistent manner. The coupled modes
of wave propagation is shown to be governed by a modified set of nonlinear
Schr\"{o}dinger-Boussinesq-like equations which admit exact solutions in form
of stationary localized envelopes. Numerical simulation reveals the existence
of large-scale density fluctuations that are self-consistently created by the
localized whistlers in a strongly magnetized high density plasma. The
conditions for the modulational instability (MI) and the value of its growth
rate are obtained. Possible applications of our results, e.g., in strongly
magnetized dense plasmas and in the next generation laser-solid density plasma
interaction experiments are discussed.Comment: 9 pages, 4 figures; To appear in Physical Review E (2010
Response to ``Comment on `Primordial magnetic seed field amplification by gravitational waves' "
Here we respond to the comment by Tsagas (gr-qc/0503042) on our paper
gr-qc/0503006. We show that the results in that comment are flawed and cannot
be used for drawing conclusion about the nature of magnetic field amplification
by gravitational waves, and give further support that the results of
gr-qc/0503006 are correct.Comment: 4 pages, 2 figures, to appear in Physical Review
Kinetic theory of electromagnetic ion waves in relativistic plasmas
A kinetic theory for electromagnetic ion waves in a cold relativistic plasma
is derived. The kinetic equation for the broadband electromagnetic ion waves is
coupled to the slow density response via an acoustic equation driven by
ponderomotive force like term linear in the electromagnetic field amplitude.
The modulational instability growth rate is derived for an arbitrary spectrum
of waves. The monochromatic and random phase cases are studied.Comment: 7 pages, 4 figures, to appear in Physics of Plasma
Short wavelength quantum electrodynamical correction to cold plasma-wave propagation
The effect of short wavelength quantum electrodynamic (QED) correction on
plasma-wave propagation is investigated. The effect on plasma oscillations and
on electromagnetic waves in an unmagnetized as well as a magnetized plasma is
investigated. The effects of the short wavelength QED corrections are most
significant for plasma oscillations and for extraordinary modes. In particular,
the QED correction allow plasma oscillations to propagate, and the
extra-ordinary mode looses its stop band. The significance of our results is
discussed.Comment: 12 pages, 5 figure
Nonlinear wave interactions in quantum magnetoplasmas
Nonlinear interactions involving electrostatic upper-hybrid (UH),
ion-cyclotron (IC), lower-hybrid (LH), and Alfven waves in quantum
magnetoplasmas are considered. For this purpose, the quantum hydrodynamical
equations are used to derive the governing equations for nonlinearly coupled
UH, IC, LH, and Alfven waves. The equations are then Fourier analyzed to obtain
nonlinear dispersion relations, which admit both decay and modulational
instabilities of the UH waves at quantum scales. The growth rates of the
instabilities are presented. They can be useful in applications of our work to
diagnostics in laboratory and astrophysical settings.Comment: 15 pages, to appear in Physics of Plasma
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