EMISSION CHARACTERISTICS OF AUSIBE FIELD-ION SOURCES

A ribbon type AuSiBe alloy field ion source, which combines the advant ages of both hairpin type sources and reservoir type sources, has been constructed. The current-voltage characteristics of this source have been investigated. Hysteresis and four differentiated emission regions ha ve been observed for them. By means of scanning electronic microsc opy, it has been established that this complicated behaviour of the I- V curves and the angular distribution of the extracted ions are associ ated with the shape of the emitting surface. The mass spectrum of the emitted ions has been determined by means of an E x B mass filter. Con siderable emission of Au+, AuBe32+, Si2+, Be2+, AuBe3+, Be+, Si+, and Au2+ has been observed.