Setsuo Saeki

Numerical simulation of hydrogen ion species in the steady-state plasma of a low-pressure ion source

Ion species ratios in a hydrogen plasma are calculated systematically as a function of plasma parameters, i.e. the electron density, the electron temperature the pressure of hydrogen gas and the plasma volume. Furthermore, in the present analysis, the recombination factor for hydrogen atoms at the wall surface of a vacuum vessel is treated as another plasma parameter. The most significant point is that ion species ratios depend strongly not only on plasma parameters but also on the recombination factor. The proton ratio increases with decreasing the value of the recombination factor. Primary electrons also play an important role for ion species ratios, and the presence of primary electrons causes the proton ratio to decrease.

Wall effects on the percentage of atomic ions in a hydrogen plasma

Abstract The ratio of ion species in hydrogen plasma is calculated numerically by using a particle balance model, where the recombination factor for hydrogen atoms at the wall is treated as another plasma parameter.

Numerical studies on volume production of negative ions in hydrogen plasmas

In order to study the mechanism of H- production due to volume processes and the dependence of H- production on plasma parameters, a comprehensive model is presented. The model considers important processes for the production of both H- and positive ions. A set of particle balance equations in a steady-state hydrogen plasma are solved simultaneously. The calculated results have confirmed that H- ions are generated by dissociative attachment to highly vibrational excited hydrogen molecules (vibrational level nu =5-10) and these molecules are produced by electrons with energies in excess of 30 eV.

Enhancement of H− production in a multicusp source by proper selection of wall material

Abstract The effect of the wall material on hydrogen ion species productions in a low-pressure plasma, especially H − ions, is studied experimentally by using a multicusp ion source. Under the same discharge conditions, Al generally produces the highest H − ion current although the difference in H − yield between Al, Cu and stainless-steel liners depends on the source pressure of hydrogen gas. At the same time, there is little difference in the plasma parameters for the three different metal liners. The present results suggest that neutral particles (i.e. atomic hydrogen (H) and vibrationally excited molecules (H ∗ 2 ))-wall interaction affects those differences in H − production.