Characterization of the time evolution of a microsecond electron beam diode with anode effects

The time-evolution of a low aspect ratio, microsecond pulse length, electron beam diode with anode plasmas, operating at initial current densities of ;Very rapid cathode plasma closure velocities of from 8-11 cu/;Before self-filling, a low effective charge cathode plasma is observed, consisting almost exclusively of components derived from hydrocarbon surface impurities rather than substrate material (aluminum primarily). Evidence for cathode plasma instabilities are also noted. After self-filling, evidence for a beam-plasma interaction leading to RF emission, beam filamentation and collective effects are suggested. A highly ionized carbon plasma (up to CIV) was observed (T;Both active (laser deflection) and passive (spectroscopy) plasma diagnostics were used to investigate the diode plasma properties and motion, and complement each other well. The deflection diagnostic is noted as an extremely useful tool for investigating diode plasmas. In this work, the results of the laser probing technique are more reliable than those of spectroscopy. The spectroscopic technique, as applied in this work, is not very reliable, since cathode and anode plasma components may be similar. Empirical techniques to determine the cathode plasma motion, based on modeling of the diode voltage and current were the least reliable.