Conformal Space-Charge Limited Emission Modeling in the Neptune EM-PIC Code

Electromagnetic Particle-in-Cell (EM-PIC) simulations of modern high-power RF amplifiers and sources have seen considerable advances in the last decade in both solution accuracy and execution time. Electromagnetic "cut-cell" algorithms capture complex device geometry conformally on 3D Cartesian grids, while EM-PIC simulation codes have been optimized for multi-core CPUs and GPU accelerators. One challenge that remains is numerically modeling the interaction of particles and fields near cut-cell boundaries, where accurately interpolating near-surface fields from the Cartesian grid presents a challenge. Of particular relevance to device simulation is modeling space-charge limited (SCL) emission from arbitrary curved surfaces, both accurately and self-consistently, to correctly determine the emitted current distribution.