SC proton linac for the CONCERT multi-users facility

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. Because of their high acceleration efficiency, superconducting cavities of elliptical shape and working at 704 MHz have been selected. The overall architecture - transition energy, number of cavities per module, cavity design and number of families - results from linac length/cost optimisation and does not depend on the duty cycle which can vary from 5% to 25%, typical values for a stand-alone and multi-users facilities, respectively. RF power generation is based on individual klystrons and pulsed IGBT high voltage power supplies. Each cavity is fed by two symmetrical couplers to achieve the required peak power and to reduce the RF kicks. With adequate beam matching between the different sections, beam dynamics 3D simulations in the absence of errors and with various realistic errors show stable beam behaviour, as well as moderate halo enhancement and emittance growths