Application of ion-implantation for activation of metal-alloyed cathodes

Full text: As cold secondary emission and the SHF cathodes till now are widely used Pd - Ba and Pt - Ba metal-alloy. Before exploitation these cathodes are thermally activated in high vacuum or in an atmosphere of various gases (H2, N2, H+N). The maximal value of secondary-emission coefficient (σm) the activated alloy is 2.5-3. Our researches have shown, that ion implantation considerably improves emission properties of materials of a various nature. In this work, influence of ion implantations on Mo, Pt and alloys Pd-Ba, Pt-Ba secondary - emission characteristics is investigated. It is established, that as a result of implantation of ions of barium with low energy (E0≤1 keV) in near surface layer Pt, Pd it is formed intermetallic connection such as Pt-Ba and Pd-Ba. Value σm for these connections is 3-3.5. It is revealed, that samples Pt and Pt-Ba the after implanted the big dose of ions Ba+ have almost identical secondary-emission parameters. Influence of the long anneal, laser annealing and an electronic bombardment on performance characteristics (value σm and eφ) cathodes was simultaneously explored. The determination, that ion-implanted samples take a considerably major current and temperature loadings concerning activated metallic-alloy cathodes. So, for example, activated Pd-Ba (concentration of Ba - 1.5 %, Pd - 98.5 %) without change of the working parameters take an electronic bombardment load up to density of a current je=1.5-2 mA/cm2, 100 and more clocks, and ion-implanted Pd-Ba is up to 3-4 mA/cm2. Change of emission properties of metallic-alloy cathodes at exterior actions explains transpiration of atoms Ba from a surface. Thus loss Ba on a surface partly makes up a diffusion of barium from bulk to surface. In case of ion-implanted sample in near-surface layer the significant amount of barium (up to 50 %) is implanted, that up to particular value of a current loading provides an intensive diffusion of barium to a surface. The even greater increase σm (up to 8-10) is observed at realization of implantation in an atmosphere of oxygen. It is shown, that ion-implanted samples can be used without preliminary activation. The topography, composition and electronic structure of surface ion-implanted samples are investigated