1988 Volume 60 Issue 6 Pages 419-435
Production of H- ions in a steady state hydrogen discharge plasma is discussed. According to the numerical calculation of a set of particle balance equations, H- ions are formed mainly by dissociative attachment of slow plasma electrons (i. e. electron temperature Te≅1eV) to highly vibrationally excited hydrogen molecules H2* (optimum vibrational level v “=7-9), and those H2* (v”) are produced mainly by collisional excitation due to fast primary electrons with energies in excess of 40 eV. On enhancement of H- yield, the effect of other H2* (v “) formation process caused by molecular ions or by atomic hydrogen is also discussed.
Although H2* (v”) is essential to the H-formation, the optimum plasma conditions for the H2* (v″) production are not compatible with those for the H- formation. In order to clarify the effectiveness of a tandem two-chamber system, the relative H- yields for single-chamber and tandem two-chamber systems are compared.
