AN ELECTRON-BEAM ION-SOURCE FOR LABORATORY EXPERIMENTS

The design and properties of an electron beam ion source (EBIS) capable of producing low-energy, highly charged ions such as Ar16+ and Xe30+ are described. The source, to be used in laboratory experiments in atomic and surface physics, utilizes a conventional, 0.42-T solenoid and an externally launched electron beam. Ultrahigh vacuum in the ionization region is created by a distributed sputter-ion pump. The source design is relatively simple, and the source is small and easy to operate. The concept of a saturated electron beam is introduced in order to explain the observed argon and xenon ion charge state evolution. Very high ion charge states can be produced by confining ions for times up to 1 s in an electron beam in which the degree of space-charge neutralization by ions is determined by potentials applied to the drift tubes.