R&D VACUUM ISSUES OF THE FUTURE GSI ACCELERATOR FACILITIES

The new GSI accelerator facilities (FAIR project) are planned to deliver heavy ion beams of increased energy and highest intensity [1]. Whereas the energy is planned to be increased roughly by a factor of 30, the ion beam intensities are planned to be enlarged by three orders of magnitude. To achieve highest beam intensities, medium charged heavy ions (e.g. U28+) are accelerated. Since the ionization cross sections for these ions are comparably high, a UHV-accelerator system with a base pressure in the low 10-12 mbar regime is required, even under the influence of ion beam loss induced desorption processes. An intensive program was started to upgrade the UHV system of the existing synchrotron SIS18 (bakeable) and to design and lay out the UHV systems of the future synchrotrons SIS100 and SIS300 (mainly cryogenic). One special technical difficulty common to SIS18 and SIS100 is the restriction on thin walled (<0.5mm), large aperture vacuum chambers, which have to withstand 300°C bakeouts or liquid helium temperatures inside the fast cycling magnets (minimum eddy – currents). The strategy of this program includes basic research on the physics of the ion induced desorption effects as well as technical developments, design and prototyping on bakeable UHV components (vacuum chambers, diagnostics, bakeout-control, pumping speed), collimator for controlled ion beam loss, NEG coating and cryogenic vacuum components