Relevance of Volume and Surface Plasma Generation of Negative Ions in Gas Discharges

The relative contribution of volume and surface-plasma generation of extracted Н- ions in gas discharge sources is analyzed. By present time, it is well known that surface-plasma generation of extracted Н- ion is dominate above volume processes in discharges with admixture of cesium or others catalysts with low ionization potential. From the analysis presented below, it follows that contrary to the standard opinion repeated in tens of publications, in the optimized discharge sources without cesium and small currents of accompanying electrons, named by authors as “pure volume sources”, a surface-plasma generation of extracted Н- ion also dominate above volume processes. For the effective generation of Н- ion beams in discharge without cesium, it is necessary to optimize surface-plasma generation of extracted Н-, D- ion that, as a rule, leads to suppression of volume production. Such optimization allows considerably improving characteristics of Н-, D- sources for accelerators and for neutral beam injectors in magnetic confinement fusion