J X B drift motion of a relativistic electron beam propagating through an ion channel is investigated for both the flat-top and the gaussian density profiles. Due to finite beam size and due to the accelerator and beam head location, location of the maximum deflection point propagates from the accelerator nozzle to the beam head. The propagation velocity of the maximum deflection point is a fraction of the beam velocity. At the maximum deflection point, the perpendicular velocity of the electron beam segment does not match to the drifting velocity of the ion channel, causing a disruption of the beam propagation through the ion channel. This disruption is particularly troublesome for the later portion of the beam. For example, for a 1 kA beam, the first one microsecond(s) portion of the beam pulse is grabbed by the ion channel, but the later portion of the beam pulse will be lost. The pulse length of the grabbed portion by ion channel is proportional to the square root of the beam current.
Han Sup Uhm, Han Sup Uhm,
"J x B drift motion of a relativistic electron beam in a long-range propagation", Proc. SPIE 1629, Intense Microwave and Particle Beams III, (1 April 1992); doi: 10.1117/12.137144; https://doi.org/10.1117/12.137144