SIMULATIONS OF PLASMA WAKEFIELD

We present 2-D cylindrical particle-in-cell simulations of the E-157 beam wakefield experiment at SLAC, in which a 30 GeV electron beam passes through 1 m of preionized Li (lithium) plasma. Plasma electrons are blown out from the axis in the wake of the electron beam, driving a strong axial electric field, E z of order 1 GV/m, in the small region where the plasma electrons fall back to the cylin-drical axis. We also simulate wakefield accelerators with much higher plasma density and a 50 GeV drive beam. Electron impact ionization of the background neutral Li is found to be significant only for plasma densities of order 1017 cm-3 or larger. Other collisional processes are also considered.