Space Charge Effects on Short-Pulse Electron Beam Dynamics

Space charge effects impose critical limitations on the transport of short-pulse electron beams, modifying density profiles and propagation dynamics. This work employs a 1- dimensional (1-D) multiple-sheet model and 2-dimensional (2-D) particle-in-cell simulations to analyze the influence of initial pulse shape, charge density, and pulse duration on beam distortion and transport. For beams in a diode with zero initial velocity, pulse distortion scales as Distortion = 3f / 4k, where f and k are the normalized charge density and pulse length, respectively. Distortion for beams with different initial velocity is also compared. It is found that the transportable current density follows the short-pulse Child–Langmuir (CL) law, regardless of the pulse shape.