Nordsieck length measurement of an intense relativistic electron beam propagating in high pressure neutral gas

Summary form only given. A conditioned 5 MeV, 20 kA, 40 ns FWHM intense relativistic electron beam produced by the SuperIBEX accelerator is injected into a 20-meter-diameter propagation tank at pressures in the 400-760 Torr range. The radial profile of the beam is measured using time-resolved optical diagnostics and a segmented concentric Faraday cup. Beam and net currents are recorded using beambugs and Rogowski monitors. These diagnostics are deployed at various positions along the axis of propagation, providing a time-resolved history of beam profile evolution. The expansion rate as a function of background pressure is then determined numerically and compared with calculations of the Nordsieck length based on input beam parameters and a given pressure.