Status and future development of ion sources for on-line mass separators

The status is given of ion sources for on-line mass separators with examples of recent developments on element availability, ionization efficiency, speed and selectivity. Since the target and the ion source are most often integrated, a discussion is included of the progress in the most methods used to bring the nuclear reaction products out of the target and into the active region of the source. A number of novel, more advanced target and ion source systems have recently emerged and may in the future offer new possibilities for existing machines. Selected examples will be given for: (1) new release and delay studies, (2) selective resonant laser ionization, (3) electron cyclotron resonance (ECR) ion sources, (4) chemical reactions inside the ion source, (5) ion sources with bunched beam release. In view of the planned new facilities with post-acceleration of radioactive ion beams or on-line to high intensity low repetition rate accelerators, a number of future requirements of the ion sources are discussed. (orig.)