7 research outputs found
Mitigation of numerical Cerenkov radiation and instability using a hybrid finite difference-FFT Maxwell solver and a local charge conserving current deposit
A hybrid Maxwell solver for fully relativistic and electromagnetic (EM)
particle-in-cell (PIC) codes is described. In this solver, the EM fields are
solved in space by performing an FFT in one direction, while using finite
difference operators in the other direction(s). This solver eliminates the
numerical Cerenkov radiation for particles moving in the preferred direction.
Moreover, the numerical Cerenkov instability (NCI) induced by the
relativistically drifting plasma and beam can be eliminated using this hybrid
solver by applying strategies that are similar to those recently developed for
pure FFT solvers. A current correction is applied for the charge conserving
current deposit to correctly account for the EM calculation in hybrid Yee-FFT
solver. A theoretical analysis of the dispersion properties in vacuum and in a
drifting plasma for the hybrid solver is presented, and compared with PIC
simulations with good agreement obtained. This hybrid solver is applied to both
2D and 3D Cartesian and quasi-3D (in which the fields and current are
decomposed into azimuthal harmonics) geometries. Illustrative results for laser
wakefield accelerator simulation in a Lorentz boosted frame using the hybrid
solver in the 2D Cartesian geometry are presented, and compared against results
from 2D UPIC-EMMA simulation which uses a pure spectral Maxwell solver, and
from OSIRIS 2D lab frame simulation using the standard Yee solver. Very good
agreement is obtained which demonstrates the feasibility of using the hybrid
solver for high fidelity simulation of relativistically drifting plasma with no
evidence of the numerical Cerenkov instability
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