Improved C− efficiency and ion beam currents by modifying SNICS cathode material

We investigated the possibility of increasing the C-14 AMS efficiency and maximizing C- beam currents by modifying sample cathode geometry and material. Previously, we reported results which showed an increase in C- beam current and improved ionization efficiency when reducing the cathode sample well diameter from 1 mm to 0.75 mm and using zinc inserts, pressed into the aluminum cathode holder [4]. In this study we expand that effort by using cathodes with inserts made of Fe, Mo, Ni, Ti, Cu, and Zn. We pressed cathodes with 100 mu g of Oxalic Acid I (OX-I) and ran them to exhaustion. C-12 beam currents, C-14 counts, and graphite weight were used to determine ion source efficiency.