Preflashover phenomena and electron‐stimulated desorption in high electric fields

摘要

The effect of high electric fields on the electron‐stimulated desorption (ESD) of positive ions from metal surfaces has been studied at fields between 103 and 105 V/cm for electron energies between 1 and 20 kV. Adsorbed gases characteristic of the residual vacuum (10-9 Torr) were detected under all conditions, but ions characteristic of the substrate were only detected for fields approaching 105 V/cm. These observations confirm that previously reported preflashover anode metal ion species in an ultrahigh‐vacuum diode originate at anode protrusions by a field evaporation process and that only residual gas species are produced prior to flashover by ESD. It is suggested that, if field emission processes at the cathode could be completely suppressed, electrical flashover would still occur, initiated and sustained by field‐evaporated anode ions.