A Universal Multiscale Method for Rapid Determination of Local Emission Current Density from Nanoscale Emitters

Herein, we discuss the use of a multiscale method based on lookup tables (LUTs) for extremely fast and mathematically accurate emission current calculations. The technique is applicable to metallic emitters of arbitrary shape, which could be of great use in particle-in-cell codes for investigating electron sources. The LUTs are prepopulated with precise calculations of local emission current density (LECD) that can be upgraded to include any higher order physics that is critical for current state-of-the-art emitters, including nanoscale emitter curvature. The method for considering the effect of curvature is discussed in detail. Early results show that the use of a LUT for LECD can speed up numerical simulations by a factor of about 1000 times while retaining high precision with a maximum error of less than one percent when compared to direct numerical solutions.