Energy transfer in the plasma wake-field accelerator

The transfer of energy from the driving beam to the trailing beam in the plasma wake-field accelerator is studied in computer simulations. We show that with an asymmetric current distribution in the driving bunch, trailing particles can gain energies up to (1+k²_pZ²)^1/2Δγmc², where Z is the bunch length and Δγmc² the average energy loss of driving electrons. Because of the relative phase slippage and the two-stream instability, the process of energy gain degrades before the driving beam loses all of its energy; however, even for γ_i=150, Δγ/γ_i>~70%, with an energy gain ~1 GeV. Transverse effects are briefly discussed.