7,545 research outputs found
Enhanced collimated GeV monoenergetic ion acceleration from a shaped foil target irradiated by a circularly polarized laser pulse
Using multi-dimensional particle-in-cell (PIC) simulations we study ion
acceleration from a foil irradiated by a circularly polarized laser pulse at
1022W/cm^2 intensity. When the foil is shaped initially in the transverse
direction to match the laser intensity profile, the center part of the target
can be uniformly accelerated for a longer time compared to a usual flat target.
Target deformation and undesirable plasma heating are effectively suppressed.
The final energy spectrum of the accelerated ion beam is improved dramatically.
Collimated GeV quasi-mono-energetic ion beams carrying as much as 18% of the
laser energy are observed in multi-dimensional simulations. Radiation damping
effects are also checked in the simulations.Comment: 4 pages, 4 figure
Tunable Circularly Polarized Terahertz Radiation from Magnetized Gas Plasma
It is shown, by simulation and theory, that circularly or elliptically
polarized terahertz radiation can be generated when a static magnetic (B) field
is imposed on a gas target along the propagation direction of a two-color laser
driver. The radiation frequency is determined by
, where is the
plasma frequency and is the electron cyclotron frequency. With the
increase of the B field, the radiation changes from a single-cycle broadband
waveform to a continuous narrow-band emission. In high-B-field cases, the
radiation strength is proportional to . The B field
provides a tunability in the radiation frequency, spectrum width, and field
strength.Comment: 6 pages, 5 figure
Non-canonical statistics of finite quantum system
The canonical statistics describes the statistical properties of an open
system by assuming its coupling with the heat bath infinitesimal in comparison
with the total energy in thermodynamic limit. In this paper, we generally
derive a non-canonical distribution for the open system with a finite coupling
to the heat bath, which deforms the energy shell to effectively modify the
conventional canonical way. The obtained non-canonical distribution reflects
the back action of system on the bath, and thus depicts the statistical
correlations through energy fluctuations
Laser opacity in underdense preplasma of solid targets due to quantum electrodynamics effects
We investigate how next-generation laser pulses at 10 PW 200 PW interact
with a solid target in the presence of a relativistically underdense preplasma
produced by amplified spontaneous emission (ASE). Laser hole boring and
relativistic transparency are strongly restrained due to the generation of
electron-positron pairs and -ray photons via quantum electrodynamics
(QED) processes. A pair plasma with a density above the initial preplasma
density is formed, counteracting the electron-free channel produced by the hole
boring. This pair-dominated plasma can block the laser transport and trigger an
avalanche-like QED cascade, efficiently transfering the laser energy to
photons. This renders a 1--scalelength, underdense preplasma
completely opaque to laser pulses at this power level. The QED-induced opacity
therefore sets much higher contrast requirements for such pulse in solid-target
experiments than expected by classical plasma physics. Our simulations show for
example, that proton acceleration from the rear of a solid with a preplasma
would be strongly impaired.Comment: 5 figure
Leibniz 2-algebras and twisted Courant algebroids
In this paper, we give the categorification of Leibniz algebras, which is
equivalent to 2-term sh Leibniz algebras. They reveal the algebraic structure
of omni-Lie 2-algebras introduced in \cite{omniLie2} as well as twisted Courant
algebroids by closed 4-forms introduced in \cite{4form}.
We also prove that Dirac structures of twisted Courant algebroids give rise
to 2-term -algebras and geometric structures behind them are exactly
-twisted Lie algebroids introduced in \cite{Grutzmann}.Comment: 22 pages, to appear in Comm. Algebr
Study on the triphenyl tetrazolium chloride– dehydrogenase activity (TTC-DHA) method in determination of bioactivity for treating tomato paste wastewater
A quick analysis of the sludge activity method based on triphenyltetrazolium chloride-dehydrogenase activity (TTC-DHA) was developed to change the rule and status of the biological activity of the activated sludge in tomato paste wastewater treatment. The results indicate that dehydrogenase activity (DHA) can effectively facilitate the biochemical reaction of tomato paste wastewater treatment upon analysis of the influences of various DHA and kinetic factors. The biological activity of the activated sludge by TTC-DHA was changed to become applicable to aeration and wastewater treatment operation and management.Key words: Tomato paste wastewater, TTC-DHA, bioactivity, active sludge
The Scaling Behavior of Classical Wave Transport in Mesoscopic Media at the Localization Transition
The propagation of classical wave in disordered media at the Anderson
localization transition is studied. Our results show that the classical waves
may follow a different scaling behavior from that for electrons. For electrons,
the effect of weak localization due to interference of recurrent scattering
paths is limited within a spherical volume because of electron-electron or
electron-phonon scattering, while for classical waves, it is the sample
geometry that determine the amount of recurrent scattering paths that
contribute. It is found that the weak localization effect is weaker in both
cubic and slab geometry than in spherical geometry. As a result, the averaged
static diffusion constant D(L) scales like ln(L)/L in cubic or slab geometry
and the corresponding transmission follows ~ln L/L^2. This is in contrast
to the behavior of D(L)~1/L and ~1/L^2 obtained previously for electrons
or spherical samples. For wave dynamics, we solve the Bethe-Salpeter equation
in a disordered slab with the recurrent scattering incorporated in a
self-consistent manner. All of the static and dynamic transport quantities
studied are found to follow the scaling behavior of D(L). We have also
considered position-dependent weak localization effects by using a plausible
form of position-dependent diffusion constant D(z). The same scaling behavior
is found, i.e., ~ln L/L^2.Comment: 11 pages, 12 figures. Submitted to Phys. Rev. B on 3 May 200
Localized Modes in Open One-Dimensional Dissipative Random Systems
We consider, both theoretically and experimentally, the excitation and
detection of the localized quasi-modes (resonances) in an open dissipative 1D
random system. We show that even though the amplitude of transmission drops
dramatically so that it cannot be observed in the presence of small losses,
resonances are still clearly exhibited in reflection. Surprisingly, small
losses essentially improve conditions for the detection of resonances in
reflection as compared with the lossless case. An algorithm is proposed and
tested to retrieve sample parameters and resonances characteristics inside the
random system exclusively from reflection measurements.Comment: 5 pages, 3 figures, to appear in Phys. Rev. Let
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