THE NEW HIGH CURRENT ION ACCELERATOR AT GSI AND PERSPECTIVES FOR LINAC DESIGN BASED ON H-MODE CAVITIES

In 1999 a new High Current Injector HSI was installed to replace the Wideroe section of the Unilac. Designed for a high mass-to-charge ratio A/q ≤ 65 it additonally provides high ion beam currents, e.g. U 4+ -ions up to 15 mA. The new linac has an RFQ section, which is 9.4 m long and uses mini-vanes inside an IH-cavity. It is followed by a 20 m IH drift-tube linac with the KONUS beam dynamics layout as used for instance for the CERN lead injector. This concept provides rf-acceleration within lens-free drift tube sections and at a strongly reduced defocusing action of the rf-fields. For the first time this concept was tested with high beam currents at a large tune depression of σ /σ 0 ~ 0.70. The application of H-mode cavities in the design of high-current proton and heavy ion linacs will be discussed on a more general base. For the energy range from 5 to 150 MeV, that is the first part of a high intensity proton machine behind the RFQ section, a new DTL concept based on Cross-Bar CH-cavities (H210-mode) is proposed. This CH structure can be designed for operation at about 350 MHz in the first section and at twice the frequency in the main section. CH-designs for room temperature and for superconducting operation will be discussed, as well as a 45 MeV, 100 mA proton linac design with a total length of 8.5 m.