
69Development of Cluster Beam Sources for Solid Materials
with 0.8 mm throat diameter was used. Typical pressures
ranged from 1 to 20 mbar. As the temperature was increased,
small clusters were produced initially, and then larger clus-
ters started to form. Cluster sizes were distributed from 10 to
120 atoms/ cluster.
3.2 Pure Expansion Source
In 1991, Gspann reported the generation of large Cesium clus-
ters with up to 2500 atoms/ cluster using nozzle expansion of
pure metal vapor without carrier gas [19]. Figure3.9 shows
the experimental equipment, which consisted of a cluster
source with ionization and acceleration devices. Cesium vapor
was ...