Propagation characteristics of a mildly relativistic electron beam in sub-Torr pressure

Summary form only given, as follows. Using a mildly relativistic electron beam (300 kV, 40 kA, 60 ns) with a foilless diode in a beam-induced plasma channel, the effect of return current has been investigated experimentally. The pressure of filling gas (air) in this experiment ranged from 10 mTorr to 100 mTorr. The net current and beam current variation were measured by a Rogowski coil and a Faraday cup. The peak return current observed at a propagation window has been characterized in terms of the beam current and the charge neutralization factor. The beam instability attributed to the return current resulted from an inductive phenomena of a beam-induced plasma channel has been observed.