Design of an apparatus for low-energy ion scattering from solid surfaces

The basic characteristics of an apparatus for experiments involving low-energy (0.1-5 keV) scattering of alkali ions from solid surfaces are presented. To produce alkali ions, a thermionic ion source was used. The ion beam obtained passes through the magnetic sector (Rm=10 cm, phi m=90 degrees ), which operates in the stigmatic focusing regime. Due to the primary beam contamination effect, surface cleaning during the experiment was maintained by the deposition of a fresh film of the metal investigated. The backscattered ions were energy-analysed by the double cylindrical sector analyser (Ra=5 cm, phi 1=90 degrees , E/ delta E approximately=400), which was continually swung around the target in the angular interval 0< theta <135 degrees . For monitoring surface cleanness during the experiment, an Auger spectrometer was used. Some results of the measured energy spectra of Na+ ions backscattered from an Ag surface are presented.