Physics of pasotrons

Summary form only given. Pasotrons (plasma assisted slow-wave oscillators) are plasma-filed microwave tubes recently developed at Hughes Research Laboratory. Among unique features of these devices are the use of plasma cathode electron guns and the use of a self-generated plasma channel for providing the electron beam transport in the absence of guiding external magnetic fields. In our paper we present the theoretical studies of the effect of radial motion of electrons on the pasotron operation, the effect of ions on this motion and the competition of axial modes in pasotrons whose slow-wave structures have significant end reflections. (The latter increases the amplitude of the wave, and thus, allows one to shorten the interaction space.) The theory developed describes a number of experimentally observed effects, for instance, such as excitation of TE-waves (which is impossible in microwave tubes driven by linear electron beams) and "pulse shortening" during the voltage rise and fall times.