Simulations of high intensity ion beam RFQ cooler for DESIR/SPIRAL 2: SHIRaC

International audienceSHIRaC is a buffer gas radiofrequency quadrupole cooler, part of SPIRAL 2 facility, at GANIL in France. It is designed to cool low energy ion beams with emittances up to 80 pi.mm.mrad and currents up to 1 mu A. It is devoted to reduce the beam parameters; less than 3 pi.mm.mrad of emittance and around 1 eV of spread energy, and to transmit more than 60% of ions. However, to achieve the least possible emittance, spread energy and ion transmission, the space charge has been overcome using high confining RF amplitude. Numerical simulations have been developed in order to study and evaluate the space charge effects on the beam parameters and the ion transmission. The simulation results have shown that the main degradations of these parameters stem from this effect. The ion transmission decreases progressively with the beam current and it nevertheless remains above 65%. The emittance and the spread energy increase with the beam current while staying below 2.4 pi.mm.mrad and 5.9 eV respectively