Modeling of longtitudinual spacecharge-effects for the monoenergetic electron beam in a laser wakefield accelerator

Particle-in-cell (PIC) codes have been widely used to model the complex processes and interactions occurring in laser- wakefield accelerators (LWFA). When all the interactions are taken into account, the dominant one or two physical mechanisms for limiting the amount of charges/currents in the monoenergetic electron beam of a LWFA become vague and hard to be analyzed. Therefore, it will be instructive if we isolate the various important mechanisms (such as space- charge & self-magnetic field effects) of an electron pulse in a LWFA and model them separately to determine the dominant mechanism without using PIC simulations (which includes all the physical mechanisms). Thus, in this paper, we focus on the modeling of space charge effects for a relativistic short electron pulse under the influence of strong longitudinal electric field (analogous to the case of a plasma bubble in a LWFA). The influence of space- charge, which limits the charge number of the electron pulse, will be evaluated. Comparison of the simplified model with PIC simulations will also be discussed.