Comparison of injection algorithms for electron beam simulation by particle-in-cell method

Algorithms of macroparticles injection into particle-in-cell computational domain for electrons beam simulation are studied. Models for Fawler-Nordheim and Gauss laws as well as constant current density injection are compared. The geometry of coaxial-cylinders diode for test-aimed device is used. In space charge limited regime Gauss law and constant current density injection are similar in resulted beam dynamics. The Fawler-Nordheim injection function, implemented in XOOPIC, is more appropriate for simulation of field emission generator of electrons beam both in cases of space charge limited and unlimited regimes.