J. Glatz, J. Klabunde, U. Scheeler, D. Wilms (GSI)
With the new GSI high current injector the beam intensity will be increased by two orders of magnitude. The operation at the high beam power required major changes in hardware, software and operating strategy. Considering the beam pulse power of up to several megawatts and the short stopping range at particles energies below 12 MeV/u, all destructive devices have to be replaced preferably by non-destructive elements or by, if unavoidable, improved destructive devices. Along the linac new beam diagnostic elements were installed, e.g. beam transformers, capacitive beam position monitors, secondary ion profile monitors. Modified beam stoppers, scrapers, slits and diaphrams were installed to avoid melting or vaporising of material. The foil stripping section in the beam transfer line to SIS had to be modified for the high power operation: a sophisticated magnetic beam sweeping system was installed. For safe accelerator operation, manual variation of parameters has to be reduced. Therefore, theoretical and practically confirmed setting values for all components of the UNILAC have to be available for automatic adjustment procedures. New operating software has been developed. The beam control was realised by fast beam transformer measurements at many positions. Transmission values below defined limits will cause a fast beam interruption. The enhanced versatility of the whole UNILAC facility is demonstrated by the three-ion operation on a pulse-to-pulse basis at 50 Hz. Since November 1999 the modified UNILAC is in routine operation, first operational experiences will be reported.
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