Surface non-uniformity including temperature

work and geometric profile affect intrinsic emittance of thermionic cathode of vacuum electronics and accelerators.In order to understand how intrinsic emittance is manipulated by work function variation

a general intrinsic emittance model consisting of contributions from surface non-uniformity was developed.Finite-difference time-domain particle-in-cell (FDTD-PIC) simulation verified numerical calculation result of cathodes with work function radical variation and 1D cosine periodic variation.Furthermore

theoretical results and simulation for cathodes with work function of 2D cosine periodic variance and 2D random distribution showed that emittance increase coefficient approaches to 1 and variance of emittance increase coefficient decreased quickly when spatial frequency increased.This paper shows that work non-uniformity hardly affects intrinsic emittance if cathode diameter is much larger than the average size of micro work region;in contrast

intrinsic emittance may differ from uniform case notably if micro size is comparable to cathode diameter.Moreover

theoretical model and simulation method are useful to assess influence of work or temperature non-uniformity on intrinsic emittance of kinds of cathode.