Collective Ion Acceleration in a Traveling Virtual Cathode

This paper describes a general class of collective acceleration schemes which rely on the controlled motion of a virtual cathode created in an intense relativistic electron beam. Preliminary numerical simulation results are presented for a specific scheme which does not depend on neutralization of the electron beam space charge. In particular, the position of virtual cathode formation appears to be adequately described by relatively simple equations. Also, electron beam turbulence due to a two-stream instability is shown to be substantially decreased by using a hollow beam and decreasing the external magnetic field strength.