Development of a compact atomic beam flux monitor based on surface ionization

We have developed a compact atomic beam flux monitor by means of surface ionization. The properties were studied by measuring various rare-earth elements (Ce, Nd, Sm, Dy, Yb). The proportional region between the beam flux and the surface ionization ion current was observed for every element, which indicates that with this monitor, the atomic beam flux can be determined from the observed ion current. For Nd, Sm, Dy, and Yb, the ion current was proportional to the atomic beam flux up to 100-200 A/s. On the other hand, the ion current for Ce saturated around the beam flux of 30 A/s. This can be explained by the fact that since the vapor pressure of Ce atoms is low they do not desorb fast enough from the filament, and the filament is covered with Ce atoms. The coverage of the filament limits the measurable range of the monitor. (author)