Positive ion oscillations in long electron beams

Positive ion oscillations occurring in a long electron beam were investigated experimentally. The predominant direction of oscillation was found to be transverse to the direction of electron flow, and the frequency of oscillation was found to be three times higher than existing theory predicts. In pulsed beams the onset time of irregularities in current flow due to positive ion formation was found to be inversely proportional to current, and in some cases positive ion effects were observed to take place within four microseconds of the beginning of the pulse.