115 research outputs found
A spectral, quasi-cylindrical and dispersion-free Particle-In-Cell algorithm
We propose a spectral Particle-In-Cell (PIC) algorithm that is based on the
combination of a Hankel transform and a Fourier transform. For physical
problems that have close-to-cylindrical symmetry, this algorithm can be much
faster than full 3D PIC algorithms. In addition, unlike standard
finite-difference PIC codes, the proposed algorithm is free of numerical
dispersion. This algorithm is benchmarked in several situations that are of
interest for laser-plasma interactions. These benchmarks show that it avoids a
number of numerical artifacts, that would otherwise affect the physics in a
standard PIC algorithm - including the zero-order numerical Cherenkov effect.Comment: 23 pages, 8 figure
Laser-plasma interactions with a Fourier-Bessel Particle-in-Cell method
A new spectral particle-in-cell (PIC) method for plasma modeling is presented
and discussed. In the proposed scheme, the Fourier-Bessel transform is used to
translate the Maxwell equations to the quasi-cylindrical spectral domain. In
this domain, the equations are solved analytically in time, and the spatial
derivatives are approximated with high accuracy. In contrast to the
finite-difference time domain (FDTD) methods that are commonly used in PIC, the
developed method does not produce numerical dispersion, and does not involve
grid staggering for the electric and magnetic fields. These features are
especially valuable in modeling the wakefield acceleration of particles in
plasmas. The proposed algorithm is implemented in the code PLARES-PIC, and the
test simulations of laser plasma interactions are compared to the ones done
with the quasi-cylindrical FDTD PIC code CALDER-CIRC.Comment: submitted to Phys. Plasma
Four-loop verification of algorithm for Feynman diagrams summation in N=1 supersymmetric electrodynamics
A method of Feynman diagrams summation, based on using Schwinger-Dyson
equations and Ward identities, is verified by calculating some four-loop
diagrams in N=1 supersymmetric electrodynamics, regularized by higher
derivatives. In particular, for the considered diagrams correctness of an
additional identity for Green functions, which is not reduced to the gauge Ward
identity, is proved.Comment: 14 pages, 9 figure
Coherence and superradiance from a plasma-based quasiparticle accelerator
Coherent light sources, such as free electron lasers, provide bright beams
for biology, chemistry, physics, and advanced technological applications.
Increasing the brightness of these sources requires progressively larger
devices, with the largest being several km long (e.g., LCLS). Can we reverse
this trend, and bring these sources to the many thousands of labs spanning
universities, hospitals, and industry? Here we address this long-standing
question by rethinking basic principles of radiation physics. At the core of
our work is the introduction of quasi-particle-based light sources that rely on
the collective and macroscopic motion of an ensemble of light-emitting charges
to evolve and radiate in ways that would be unphysical when considering single
charges. The underlying concept allows for temporal coherence and superradiance
in fundamentally new configurations, providing radiation with clear
experimental signatures and revolutionary properties. The underlying concept is
illustrated with plasma accelerators but extends well beyond this case, such as
to nonlinear optical configurations. The simplicity of the quasi-particle
approach makes it suitable for experimental demonstrations at existing laser
and accelerator facilities.Comment: 15 pages, 4 figure
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