Present status of numerical modeling of hydrogen negative ion source plasmas and its comparison with experiments: Japanese activities and their collaboration with experimental groups

Abstract

The present status of kinetic modeling of particle dynamics in hydrogen negative ion (H ^− ) source plasmas and their comparisons with experiments are reviewed and discussed with some new results. The main focus is placed on the following topics, which are important for the research and development of H ^− sources for intense and high-quality H ^− ion beams: (i) effects of non-equilibrium features of electron energy distribution function on volume and surface H ^− production, (ii) the origin of the spatial non-uniformity in giant multi-cusp arc-discharge H ^− sources, (iii) capacitive to inductive (E to H) mode transition in radio frequency-inductively coupled plasma H ^− sources and (iv) extraction physics of H ^− ions and beam optics, especially the present understanding of the meniscus formation in strongly electronegative plasmas (so-called ion–ion plasmas) and its effect on beam optics. For these topics, mainly Japanese modeling activities, and their domestic and international collaborations with experimental studies, are introduced with some examples showing how models have been improved and to what extent the modeling studies can presently contribute to improving the source performance. Close collaboration between experimental and modeling activities is indispensable for the validation/improvement of the modeling and its contribution to the source design/development.

Keywords

• negative ion source
• PIC-MCC modeling
• ion–ion plasma
• arc-discharge plasma
• RF-ICP plasma
• beam extraction