Rf linac and storage ring - perspectives of heavy-ion fusion studies at GSI

After many years of theoretical studies of the rf-linac/storage-ring scenario, we at GSI are now close to the completion of a two-ring accelerator complex, which will allow unique contributions to the development of HIF owing to its high operational flexibility. The availability of a high-current injector, together with charge stripping and beam cooling, allows to simulate by experiment nearly all crucial questions that can be raised for a full-scale driver accelerator based on conventional technology. The high-intensity development of SIS/ESR will be beneficial to target experiments in the range of a few kJ beam energy. From theoretical estimates with electron-cooled Xe beams we predict temperatures in solid gold of 20 eV average or 50 eV at the end of range. After this goal has been reached, plans for future development into the range of temperatures exceeding 100 eV (when radiation effects become significant) could go along one of the following directions: a more conventional approach that requires a stack of six additional rings in a common tunnel of 10 m radius; or only one such additional ring but with non-Liouvillian pulse stacking through a stripping foil. Problems to be studied in the future are briefly outlined. (orig.)