Prebreakdown currents of vacuum tubes with increased pressure stressed with AC voltage

Prebreakdown currents at AC are mainly determined by emission currents, if the capacitive current component is compensated. Under certain conditions, which are dealt with in this study, HF (high-frequency) impulse currents are superimposed. The shape of the HF impulse current curve as a function of time was recorded with a high time resolution. The steepness of relevant current jumps has been evaluated. On the basis of the results the phenomenon of HF impulse currents is interpreted as a consequence of changing gas attachment to the metallic electrodes