The 70 MeV p-Injector Design for FAIR

Abstract

The new FAIR facility at GSI will include a research program with antiproton beams besides a largely extended activity with heavy ion beams. The requested antiproton production rate of 7•10 10 has to be achieved with a linac-synchrotron SIS12-SIS100 accelerator configuration. Therefore GSI needs now a high intensity, pulsed proton linac as an independent new linac, additionally to the heavy ion linac injector UNILAC. A novel compact p linac for an operating frequency of 352 MHz has been designed. It is based on an RFQ of the 4-rod type or alternatively of the 4window type followed by a CrossBar H-type (CH)-DTL ranging from 3 MeV up to 70 MeV. At an aperture diameter of 20 mm these structures will reach effective shunt impedances between 100 MΩ/m and 40 MΩ/m (high energy end). 11 independently phased cavities with focusing quadrupole triplets in the intertank sections will provide 67 MV effective voltage gain within a total length of 21 m. Beam dynamics studies are promising. Depending on the beam current, the needed transverse emittance is defined by the multiturn injection scheme into the horizontal phase space of SIS12. It is aimed to fill up to 7•10 12 protons into SIS12 within 25µs at linac currents around 70 mA and at a normalized horizontal beam emittance of 3 µm. The energy spread has to be kept within ± 1•10-3. This design was also guided by available 352 MHz klystrons with peak rf power levels slightly above 1 MW.

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