Anode material outgassing at 250 A/cm2 current density under UHV conditions

Summary form only given. This presentation describes a study on gas evolution of plasma expansion in a reflex-triode virtual cathode oscillator (vircator) at ultra-high vacuum (UHV). Research has shown that explosive electron emission (EEE) processes at the cathode and ion / electron bombardment at the anode cause material erosion that produces regions of localized plasma. This plasma expansion has shown to lower gap impedance, cut off microwave performance and spoil low vacuum levels over time¹. The goal of the study is to identify the gas species and their sources to better understand and limit the negative effects of plasma expansion in sealed tubes. The vacuum tube under investigation is a triode-geometry vircator with 20 cm² cathode surface, driven by a 80 J Marx Generator with an approximate peak voltage and current, and pulse width of 200 kV and 5 kA, and 200 ns, respectively.