Release studies of elementary and metal-fluoride ions at the GSI on-line mass separator

Abstract

By using the techniques of implantation of heavy ions and of bunched-beam release at the GSI on-line mass separator, systematic release studies were performed. With the first technique the complete release process from the catcher-ionsource-system is analyzed in detail for 31 new tracer-host combinations. These include as new tracers the elements Ti, V, Zn, Sb, and Dy, and carbon foils of around 1 mg/cm 2 thickness as new catcher matrix. The carbon foils allow for a more reliable determination of rracer diffusion properties in carbon, avoiding the problems with porous sinter-graphites, where closed pores, inconsistencies in the manufacturer's data on grain size, or grain growth cause unacceptably large discrepancies within the derived diffusion coefficients. Measured with the bunched-beam-release technique, the mean adsorption times of the fluorides of group IIA and IIIA metals turned out to be orders of magnitude shorter than for the respective atoms, thus showing quantitatively the benefits of the CF 4-fluorination technique. The degree to which the respective alkali-fluoride ions are suppressed was determined to be < 10 −5, compatible with zero. The degree of fluorination is high in most cases, even for very low CF 4 partial pressures.