ION-ASSISTED ELECTRON-EMISSION FROM A CATHODE IN AN ELECTRIC-ARC

The effect of the presence of ions near the metal surface on the elect ron field emission by an are cathode is studied theoretically. An impo rtant electron emission process is shown to be mediated by the neutral ization of the ions: one electron from the metal is captured by each i on to form an excited neutral atom which is then ionized by the macros copic field. The neutralization-ionization rates are obtained for Heions in front of a metal surface for different fields and then used to evaluate the electron emission. This ion-assisted process contributes significantly to the electron emission, well below the top of the Sch ottky barrier. The contribution of this resonant process to the cathod e heating is also evaluated.