ION-SOURCE DEVELOPMENT FOR THE ONLINE ISOTOPE SEPARATOR AT GSI

The progress in the understanding of ion sources for isotope separation on-line and the feasibility of bunched beams of relatively refractory elements is reported. The ultra-high temperature FEBIAD-H ion source, facilitating the mounting of catchers and window compared to the earlier F-version, enables bunched beams of the elements with adsorption enthalpies up to almost 6 eV, e.g. of Be, Al, Ca, Cr, Fe, Co, Ni, Sr, Pd, Ba, Yb, and Au. This way chemical selectivity for these elements may also be achieved, at least to some extent, for isotopes with halflives greater than or similar to 1 min, including especially the difficult separation of alkaline-earth isotopes from isobaric alkalines. These studies also reveal, however, a principal difficulty in the on-line separation of refractory elements, namely their tendency, increasing with DELTA-H(a), to re-diffuse after release from the catcher into the bulk of the hot source enclosure.