The ionization efficiencies of the high work function metal sheets
such as Ta
Fe
W
Ni
Re and Pt ionizers
were studied and compared between them by calculating the degree of ionization and positive ion densities as well as measuring the target currents and negative ion beam intensities. It was shown that Fe as a kind of general metal
was also a better ionization material. The effects of surface temperature
pressure of cesium vapour and surface work function on the surface ionization process were also discussed.