The Effect of Asymmetric Plasma Plumes on the Transport of High-current Electron Beams

Advanced accelerator-based radiographic diagnostics require multiple high-current electron beam pulses for temporal resolution. The use of “kicked” beams or the failure of a transport element on a prior pulse can result in the production of a plasma plume from locations where the beam sweeps across the beam pipe, due to high thermal deposition by the beam. It is possible for this plasma to evolve to significant sizes (a substantial fraction of the pipe radius) over the course of several pulses. This asymmetric plume can then have deleterious effects on the transport of subsequent beam pulses due to dynamic image charge and current effects, as well as ion emission into the beam, even if the beam does not pass directly through the plume. Some of these effects on beam deflection and emittance will be examined as a demonstration of three-dimensional numerical studies using highly customized desktop-based tools.