EZ: An Efficient, Charge Conserving Current Deposition Algorithm for Electromagnetic Particle-In-Cell Simulations

TL;DR

EZ is a new charge-conserving current deposition algorithm for PIC simulations that combines existing methods to improve performance while maintaining accuracy, especially optimized for GPU implementations.

Contribution

Introduces EZ, a hybrid current deposition algorithm that enhances performance in PIC simulations without sacrificing charge conservation.

Findings

EZ achieves similar charge conservation as Esirkepov's method.

EZ outperforms in macro-particle assignment-functions up to third-order.

Provides guidelines for GPU-optimized implementation.

Abstract

We present EZ, a novel current deposition algorithm for particle-in-cell (PIC) simulations. EZ calculates the current density on the electromagnetic grid due to macro-particle motion within a time step by solving the continuity equation of electrodynamics. Being a charge conserving hybridization of Esirkepov's method and ZigZag, we refer to it as ``EZ'' as shorthand for ``Esirkepov meets ZigZag''. Simulations of a warm, relativistic plasma with PIConGPU show that EZ achieves the same level of charge conservation as the commonly used method by Esirkepov, yet reaches higher performance for macro-particle assignment-functions up to third-order. In addition to a detailed description of the functioning of EZ, reasons for the expected and observed performance increase are given, and guidelines for its implementation aiming at highest performance on GPUs are provided.