5 research outputs found
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
Accuracy of the Explicit Energy-Conserving Particle-in-Cell Method for Under-resolved Simulations of Capacitively Coupled Plasma Discharges
The traditional explicit electrostatic momentum-conserving Particle-in-cell
algorithm requires strict resolution of the electron Debye length to deliver
numerical accuracy. The explicit electrostatic energy-conserving
Particle-in-Cell algorithm alleviates this constraint with minimal modification
to the traditional algorithm, retaining its simplicity and ease of
parallelization and acceleration on modern supercomputing architectures. In
this article we apply the algorithm to model a one-dimensional radio-frequency
capacitively coupled plasma discharge relevant to industrial applications. The
energy-conserving approach closely matches the results from the
momentum-conserving algorithm and retains accuracy even for cell sizes up to 8x
the electron Debye length. For even larger cells the algorithm loses accuracy
due to poor resolution of steep gradients in the radio-frequency sheath. This
can be amended by introducing a non-uniform grid, which allows for accurate
simulations with 9.4x fewer cells than the fully resolved case, an improvement
that will be compounded in higher-dimensional simulations. We therefore
consider the explicit energy-conserving algorithm as a promising approach to
significantly reduce the computational cost of full-scale device simulations
and a pathway to delivering kinetic simulation capabilities of use to industry
A Multi Level Multi Domain Method for Particle In Cell Plasma Simulations
A novel adaptive technique for electromagnetic Particle In Cell (PIC) plasma
simulations is presented here. Two main issues are identified in designing
adaptive techniques for PIC simulation: first, the choice of the size of the
particle shape function in progressively refined grids, with the need to avoid
the exertion of self-forces on particles, and, second, the necessity to comply
with the strict stability constraints of the explicit PIC algorithm. The
adaptive implementation presented responds to these demands with the
introduction of a Multi Level Multi Domain (MLMD) system (where a cloud of
self-similar domains is fully simulated with both fields and particles) and the
use of an Implicit Moment PIC method as baseline algorithm for the adaptive
evolution. Information is exchanged between the levels with the projection of
the field information from the refined to the coarser levels and the
interpolation of the boundary conditions for the refined levels from the
coarser level fields. Particles are bound to their level of origin and are
prevented from transitioning to coarser levels, but are repopulated at the
refined grid boundaries with a splitting technique. The presented algorithm is
tested against a series of simulation challenges