PROPAGATION OF SHORT ELECTRON PULSES IN A PLASMA CHANNEL

We report the near-steady state propagation over long distance of a 25 psec, tightly focused relativistic electron beam which creates, by ra dial ejection of plasma electrons, a focusing ion channel in a plasma of electron density smaller than the beam. A dense beam core, close in radius to the injected beam, which was nearly matched to the ion focu sing strength, is observed at the plasma exit. Time-resolved imaging c onfirms that this core is situated in the trailing half of the beam, a s predicted by analytical and computer models. We discuss the impact o f these results on plasma wake field acceleration schemes.