A triply differentially pumped supersonic beam target for high-resolution collision studies

A Campargue-type source of an intense, triply differentially pumped superso nic beam of atoms (He, Ne, Ar) and molecules (N-2) for use in high-resoluti on collision experiments is described. Using stagnation pressures of (1-10) bar, nozzle diameters of (0.05-0.25) mm, and skimmer diameters of (0.5-1.0 ) mm, the center-line intensity and collimated target density are quantitat ively characterized by electron impact ionization in conjunction with total ion collection. Optimum densities in a target plane, located about 160 mm from the nozzle, range from 10(12) cm(-3) (N-2) to 8x10(12) cm(-3) (He) at background densities which are about 1% of the beam densities. The results are compared with values calculated for ideal supersonic expansions. (C) 20 00 American Institute of Physics. [S0034-6748(00)05011-5].