Improved Beam Dynamics and Cavity RF Design for the FAIR Proton Injector

The FAIR facility at GSI requires a dedicated 70 MeV, 70 mA proton injector for the research program with intense antiproton beams. The main accelerator part consists of six 'Crossbar H-type' (CH) cavities operated at 325 MHz. Based on a linac layout carefully developed over several years, recently the beam dynamics has been revised with the scope of finalising the design and thus being able to start the construction of the main linac components. As compared to previous designs the MEBT behind the RFQ was slightly extended, the gap numbers per CH cavity and the voltage distributions were optimised and the layout of the intermediate diagnostics section including a rebuncher cavity at 33 MeV was redesigned. Finally, detailed machine error studies were performed in order to check the error response of the new design and the steering concept in particular. In the consequence, the final parameters obtained from the beam dynamics update are used for finalizing the CH-DTL cavity design by CST-MWS calculations.