Speaker
Description
Introduction of cesium (Cs) into an ion sources enhances the production of negative hydrogen (H$^-$) ions while suppresses the co-extracted electron current by reducing the work function of the plasma grid surface [1-2]. However, cesium injection into an ion sources should require periodical maintenance and can add serious complexity in operation in a strong neutron /gamma radiation environment. Thus, the development of Cs-free H$^-$ / D$^-$ sources is desirable.
We have been investigating the amount of H$^-$ current and the amount of co-extracted electron current when C12A7 electride or molybdenum (Mo) were used for the Plasma electrode (PE) in a compact ECR ion source with an exchangeable PE. The C12A7 electride has a low work function, and it is expected to increase the amount of H$^-$ ion current and suppress the co-extracted electron current when used as the PE material [3]. In this study, we focus on the H$^-$ ion extraction and electron coextraction due to the shape of the PE of a H$^-$ ion source. Two materials: Mo and C12A7 electride are examined for a search of extraction structure suitable for a Cs-free ion source.
