Intense Reb Transport in a Weakly Magnetized Plasma*

Intense relativistic electron beams (REBs) have been used in various applications for the purpose of high-power microwave (HPM) generation. By injecting the beam into a plasma, it is possible to overcome the space-charge limiting current because of charge and current neutralization provided by the plasma. Our goal in this experiment was to study beam transport issues which may be relevant to the development of HPM sources which use intense REBs. We conducted high-power REB-plasma interaction experiments by injecting a 1.4 MeV, 25 kA electron beam with nb ~ 4 x 10 cminto a preformed, partially ionized ( < 1 %) argon background situated within a 15 em ID Lucite tube, with ne ~ 1011 cm-3 • Our experimental apparatus consisted of the electron beam accelerator, a plasma source, magnetic field coils, and beam, plasma, and microwave diagnostics. The beam diagnostics included a streak camera and Rogowski coils to measure beam profiles and net current in the system, respectively. A microwave interferometer provided plasma density measurements around the time of the beam-plasma interaction. We also measured RF emission using a microwave spectrometer. These data will be presented. Particle-in-cell code simulations have been performed to help us understand the relevant physics. We shall present the results of these computations.