Numerical study of cesium effects on negative ion production in volume sources

Effects of cesium vapor injection of H- production in a tandem negative ion source are studied numerically as a function of plasma parameters. Model calculation is done by solving a set of particle balance equations in a steady-state hydrogen discharge plasmas. Here, the results which focus on gas pressure and electron temperature dependences of H- volume production are presented and discussed. With including H- surface production processes caused by both H atoms and positive hydrogen ions, enhancement of H-production and pressure dependence of H- production observed experimentally are well reproduced in the model. To enhance H- production, however, so-called electron cooling is not so effective if plasma parameters are initially optimized with the use of magnetic filter. (author)