Measuring sputtering yields of high energy heavy ions on metals

For measuring sputtering yields with MeV heavy ions only low current densit ies can be used in order to avoid excessive target heating. Consequently se lf-cleaning of the target surface during the irradiation cannot be achieved and a contamination free surface has to be maintained by means of UHV cond itions. A UHV-setup including a differential pumping system has been design ed and operated at a vacuum of 10(-10) mbar during experiments. Sputtered p articles were collected on Si catchers and subsequently measured by two dif ferent surface analysis methods: Total Reflection X-Ray Fluorescence (TXRF) , and Heavy Ion Rutherford Backscattering Spectrometry (HI-RBS), In-situ su rface cleaning by 8 keV Xe ions as well as online monitoring by ERDA were f ound to be essential. With sufficient precautions on the surface conditions reproducible sputtering yields were obtained. First measurements for 230 M eV Au ions on Au, Zr, and Ti targets are presented. (C) 1998 Elsevier Scien ce B.V. All rights reserved.