Determination of Breakdown Voltages and Instabilities in Electron Beam Ionized Discharges

Diffuse electron-beam ionized discharges break down into arc discharges under three different conditions: static (no discharge orE-beam), dynamic (discharge on) and pulsed (inductive) overvoltage at switch-off. Dynamic breakdown voltages are lower than static breakdown voltages but in normal operation the discharge "on" voltage is kept to a minimum. The maximum load voltage will only be present for a few microseconds or less at switch-off; the hold-off voltage required for this condition is the pulse breakdown voltage. Using an inductive load, pulse breakdown voltages were measured at values much higher than their dynamic breakdown voltages. During conduction, certain high conductivity gases such as methane can exhibit current oscillations caused by the negative slope of their electron drift velocity as function of electric field. These oscillations have been measured electrically and optically. The range where oscillations occur can be avoided in practical applications.