64 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
Demonstration of relativistic electron beam focusing by a laser-plasma lens
Laser-plasma technology promises a drastic reduction of the size of high
energy electron accelerators. It could make free electron lasers available to a
broad scientific community, and push further the limits of electron
accelerators for high energy physics. Furthermore the unique femtosecond nature
of the source makes it a promising tool for the study of ultra-fast phenomena.
However, applications are hindered by the lack of suitable lens to transport
this kind of high-current electron beams, mainly due to their divergence. Here
we show that this issue can be solved by using a laser-plasma lens, in which
the field gradients are five order of magnitude larger than in conventional
optics. We demonstrate a reduction of the divergence by nearly a factor of
three, which should allow for an efficient coupling of the beam with a
conventional beam transport line
Particle-in-Cell Simulations of Relativistic Magnetic Reconnection with Advanced Maxwell Solver Algorithms
Relativistic magnetic reconnection is a non-ideal plasma process that is a
source of non-thermal particle acceleration in many high-energy astrophysical
systems. Particle-in-cell (PIC) methods are commonly used for simulating
reconnection from first principles. While much progress has been made in
understanding the physics of reconnection, especially in 2D, the adoption of
advanced algorithms and numerical techniques for efficiently modeling such
systems has been limited. With the GPU-accelerated PIC code WarpX, we explore
the accuracy and potential performance benefits of two advanced Maxwell solver
algorithms: a non-standard finite difference scheme (CKC) and an
ultrahigh-order pseudo-spectral method (PSATD). We find that for the
relativistic reconnection problem, CKC and PSATD qualitatively and
quantitatively match the standard Yee-grid finite-difference method. CKC and
PSATD both admit a time step that is 40% longer than Yee, resulting in a ~40%
faster time to solution for CKC, but no performance benefit for PSATD when
using a current deposition scheme that satisfies Gauss's law. Relaxing this
constraint maintains accuracy and yields a 30% speedup. Unlike Yee and CKC,
PSATD is numerically stable at any time step, allowing for a larger time step
than with the finite-difference methods. We found that increasing the time step
2.4-3 times over the standard Yee step still yields accurate results, but only
translates to modest performance improvements over CKC due to the current
deposition scheme used with PSATD. Further optimization of this scheme will
likely improve the effective performance of PSATD.Comment: 19 pages, 10 figures. Submitted to Ap
Exascale and ML Models for Accelerator Simulations
Computational modeling is essential to the exploration and design of advanced particle accelerators. The modeling of laser-plasma acceleration and interaction can achieve predictive quality for experiments if adequate resolution, full geometry and physical effects are included.
Here, we report on the significant evolution in fully relativistic full-3D modeling of conventional and advanced accelerators in the WarpX and ImpactX codes with the introduction of Exascale supercomputing and AI/ML models. We will cover the first PIC simulations on an Exascale machine, the need for and evolution of open standards, and based on our fully open community codes, the connection of time and space scales from plasma to conventional beamlines with data-driven machine-learning models
From Compact Plasma Particle Sources to Advanced Accelerators with Modeling at Exascale
Developing complex, reliable advanced accelerators requires a coordinated,
extensible, and comprehensive approach in modeling, from source to the end of
beam lifetime. We present highlights in Exascale Computing to scale accelerator
modeling software to the requirements set for contemporary science drivers. In
particular, we present the first laser-plasma modeling on an exaflop
supercomputer using the US DOE Exascale Computing Project WarpX. Leveraging
developments for Exascale, the new DOE SCIDAC-5 Consortium for Advanced
Modeling of Particle Accelerators (CAMPA) will advance numerical algorithms and
accelerate community modeling codes in a cohesive manner: from beam source,
over energy boost, transport, injection, storage, to application or
interaction. Such start-to-end modeling will enable the exploration of hybrid
accelerators, with conventional and advanced elements, as the next step for
advanced accelerator modeling. Following open community standards, we seed an
open ecosystem of codes that can be readily combined with each other and
machine learning frameworks. These will cover ultrafast to ultraprecise
modeling for future hybrid accelerator design, even enabling virtual test
stands and twins of accelerators that can be used in operations.Comment: 4 pages, 3 figures, submitted to the 20th Advanced Accelerator
Concepts Workshop (AAC22
Absorption of charged particles in perfectly matched layers by optimal damping of the deposited current.
Elimination of numerical Cherenkov instability in flowing-plasma particle-in-cell simulations by using Galilean coordinates.
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