Conditions for the self-destruction of a pulsed intense relativistic electron beam

It has been found that the stable flow of a magnetically focused unneutralized intense relativistic electron beam (IREB) depends on beam front parameters (e.g., current and voltage rise times) and on the geometry of the propagation region (e.g., length). It is argued in this letter that a pulsed IREB is susceptible to a two-stream instability resulting from reflection of electrons from the beam front. This effect may have to be taken into account in IREB applications involving fast rise times and/or long drift lengths, such as ion accelerators, electron autoaccelerators, and intense microwave generators.