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Dynamic behavior of thermionic dispenser cathodes under ion bombardment

2001; American Institute of Physics; Volume: 89; Issue: 8 Linguagem: Inglês

10.1063/1.1356433

1520-8850

R. Cortenraad, A. W. Denier van der Gon, Hidde H. Brongersma, Georg Gärtner, D. Raasch, A. Manenschijn,

Ion-surface interactions and analysis

We have investigated the surface coverage and electron emission of thermionic dispenser cathodes during 3 keV Ar+ ion bombardment, thereby simulating the bombardment of the cathodes by residual gases that takes place in cathode-ray tubes as used in television sets. During the ion bombardment at the operating temperature of 1030 °C, a dynamic equilibrium is established between the sputter removal and resupply mechanisms of the Ba and O atoms that form the dipole layer on the cathode substrate. We demonstrated that the performance of the cathodes under ion bombardment is governed by the O removal and resupply rates. It was found that the Ba resupply rate is almost an order of magnitude higher than the O resupply rate, but that the Ba can only be present on the surface bound to O atoms. Therefore, the Ba/O ratio is approximately equal to unity during the ion bombardment. Based on the investigations of the removal and resupply processes, we proposed a model that accurately describes the surface coverage and electron emission during the ion bombardment, including the dependence of the ion flux and cathode temperature.