Dynamic behavior of IREB in a collective ion acceleration experiment

Summary Form only given, as follows. An experimental study of dynamic behavior of net current in conjunction with collective ion acceleration is reported. In the presence of neutral gas, the injected IREB is subject to charge and current neutralizations, resulting in a complicated time- and space-dependent beam distribution in the drift tube. To investigate the dynamic behavior of the current in the drift tube, typically a 0.5 MeV, 70-kA, 100-ns electron beam of 2.54-cm diameter is injected through a foil anode into a drift tube of 15-cm diameter. Reproducibility of experiment was improved by using a specially designed anode system with a foil changer that allowed the production of many shots of high-current electron beam without disturbing the vacuum condition. The peak value of net current increased up to that of diode current as the hydrogen gas pressure increased until it reached a critical value P/sub c/=50 mtorr. As the pressure increased beyond P/sub c/, the peak current dropped exponentially with a decay constant of approximately 1 torr. The current waveforms showed a few distinctive features that can be attributed to the time-dependent charge and current neutralizations of the beam.<>