Analysis of Plasma Distribution near the Extraction Region in Negative Ion Sources with Surface and Volume Produced Negative Ions

Abstract

Plasma distributions near the extraction region in a hydrogen negative ion source are investigated analytically. Where surface produced hydrogen negative ions and volume produced hydrogen negative ions are considered in addition to electrons and hydrogen positive ions. The plasma-sheath equation is derived analytically and the distributions of the electric potential and the plasma density near the extraction region are obtained by solving the plasma-sheath equation. It is shown that the region consisting of the positive ions and the negative ions more than the electrons is formed near the extraction region for a case of large production rate of the negative ions. Dependence of the plasma density on the temperature of the negative ions is also shown.