17,833 research outputs found
Analytical model for the uncorrelated emittance evolution of externally injected beams in plasma-based accelerators
This article introduces an analytical formalism for the calculation of the
evolution of beam moments and the transverse emittance for beams which are
externally injected into plasma wakefield accelerators. This formalism is then
applied to two scenarios with increasing complexity - a single beam slice
without energy gain and a single beam slice with energy gain, both propagating
at a fixed co-moving position behind the driver. The obtained results are then
compared to particle-in-cell (PIC) simulations as well as results obtained
using an semi-analytic numerical approach (SANA). We find excellent agreement
between results from the analytical model and from SANA and PIC
Warp-X: a new exascale computing platform for beam-plasma simulations
Turning the current experimental plasma accelerator state-of-the-art from a
promising technology into mainstream scientific tools depends critically on
high-performance, high-fidelity modeling of complex processes that develop over
a wide range of space and time scales. As part of the U.S. Department of
Energy's Exascale Computing Project, a team from Lawrence Berkeley National
Laboratory, in collaboration with teams from SLAC National Accelerator
Laboratory and Lawrence Livermore National Laboratory, is developing a new
plasma accelerator simulation tool that will harness the power of future
exascale supercomputers for high-performance modeling of plasma accelerators.
We present the various components of the codes such as the new Particle-In-Cell
Scalable Application Resource (PICSAR) and the redesigned adaptive mesh
refinement library AMReX, which are combined with redesigned elements of the
Warp code, in the new WarpX software. The code structure, status, early
examples of applications and plans are discussed
Effects of Hyperbolic Rotation in Minkowski Space on the Modeling of Plasma Accelerators in a Lorentz Boosted Frame
Laser driven plasma accelerators promise much shorter particle accelerators
but their development requires detailed simulations that challenge or exceed
current capabilities. We report the first direct simulations of stages up to 1
TeV from simulations using a Lorentz boosted calculation frame resulting in a
million times speedup, thanks to a frame boost as high as gamma=1300. Effects
of the hyperbolic rotation in Minkowski space resulting from the frame boost on
the laser propagation in the plasma is shown to be key in the mitigation of a
numerical instability that was limiting previous attempts
The Effect of Coherent Structures on Stochastic Acceleration in MHD Turbulence
We investigate the influence of coherent structures on particle acceleration
in the strongly turbulent solar corona. By randomizing the Fourier phases of a
pseudo-spectral simulation of isotropic MHD turbulence (Re ), and
tracing collisionless test protons in both the exact-MHD and phase-randomized
fields, it is found that the phase correlations enhance the acceleration
efficiency during the first adiabatic stage of the acceleration process. The
underlying physical mechanism is identified as the dynamical MHD alignment of
the magnetic field with the electric current, which favours parallel
(resistive) electric fields responsible for initial injection. Conversely, the
alignment of the magnetic field with the bulk velocity weakens the acceleration
by convective electric fields - \bfu \times \bfb at a non-adiabatic stage of
the acceleration process. We point out that non-physical parallel electric
fields in random-phase turbulence proxies lead to artificial acceleration, and
that the dynamical MHD alignment can be taken into account on the level of the
joint two-point function of the magnetic and electric fields, and is therefore
amenable to Fokker-Planck descriptions of stochastic acceleration.Comment: accepted for publication in Ap
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