Low energy part of the CONCERT high-power proton linac

The 1.3 GeV linac of the CONCERT multi-users facility has to accelerate protons and H^- ions in a series of current pulses distributed over each 20 ms period. The peak current is identical for all pulses to keep the space charge forces about constant apart from a slight emittance change between H⁺ and H^- bunches. The beam power required for a given application is then obtained by adjusting the pulse duration with a total maximum power of 20 MW and 5 MW for the proton and H^- beams respectively. The reference design of the low-energy part of this linac is made-up of two separate proton and Hⁱnjectors up to 23 MeV, the H^- one using a funnelling system. These injectors are followed by a series of copper cavities up to the transition with superconducting cavities at about 185 MeV. The overall architecture, the technical choices and the beam dynamics in this high-power proton linac front end are presented and discussed