A microwave discharge atom beam source of high intensity

Abstract

A 2.45 GHz microwave discharge atom beam source of compact design has been developed. A standard extended quarter wavelength cavity design has been used in conjunction with a simple discharge tube and cooling arrangement. The source, while primarily designed for the production of atomic hydrogen, has also been tested with oxygen and nitrogen. The characteristics of the microwave source are compared with those of a Slevin type RF source and the influence of different cleaning procedures on performance have been investigated. Unlike the Slevin source the performance of the microwave source is not critically dependent on the cleaning procedure or gas purity. For hydrogen, both sources could provide a dissociation fraction of about 90% but the beam intensity obtainable from the microwave source (>1014 atoms cm-3) at the exit of a 1 mm capillary tube was significantly greater than that from the Slevin source. For oxygen, where the performance of the Slevin source was poor, the microwave source provided a dissociation fraction of up to about 60% and a beam density of about 1013 atoms cm-3.