Decay of electron beam current in the presence of relativistically intense space charge wave

A numerical study of evolution of plasma electrons propagating as a beam against a background of cold homogeneous immobile ions in the presence of a relativistically intense space charge wave, has been carried out using 1D relativistic particle-in-cell code. It is observed that the electron beam current diminishes with time when perturbed longitudinally by imposing a relativistically intense wave. This novel effect is attributed to phase mixing phenomena arising because of variation of relativistic electron mass. Study has been conducted for various values of flow velocities (v₀/c) and relativistic intensities (eE₀/mω_pec) of the perturbed wave. It is found that the rate of decrease of current decreases with increasing flow velocity and increases with increasing wave intensity. An analytical study of evolution of relativistic electron beam propagating through a cold homogeneous plasma with immobile ions has also been carried out by employing the method of Lagrangian transformation. The above mentioned results may be of relevance in fast-ignition scenarios.