Space-Charge Wavegrowth and Propagation on a Relativistic Electron Beam

A study into the growth and propagation of space charge waves on relativistic electron beams is currently in progress. The waves are grown by transporting an annular beam (180-200 kV, 0.8-1 kA, 300-400 ns) through a disc loaded cavity system. Measurements of the R. F. signal inside the slow wave structure and at both ends of this region show the presence of backward as well as forward space charge waves. In addition measurements of the average drift velocity of the beam electrons show high energy losses to the cavity system. Interactions between the beam, the cavity system, and at the discontinuity between the cavities and the uniform drift tube produce both fast and slow waves. Results showing this aspect of the wavegrowth processes and their effect on beam propagation are reported. The relevance of the results to collective acceleration are discussed.