Negative Ion Emission from Oxide-Coated Cathodes: II

The present paper describes a detailed study of negative ion emission processes from oxide cathodes during all stages of cathode life, using two types of mass spectrometer having oxide cathode sources. The main ions found were those of mass numbers 12, 16, 26, 27, 32, 35, 37, 42 and 43. A retarding potential method was employed to determine energy distributions of all the ions, and special attention was paid to ions emitted during activation, it being found that any oxygen evolved during activation was in an uncharged state. Variations in ion emission due to cathode temperature and applied field were also studied.