An RF beam sweeper for purifying in-flight produced secondary ion beams at ATLAS

A new large-acceptance RF beam sweeper was designed, constructed and put into operation with the goal to remove the energy-degraded primary beams tails from radioactive beams (RIB) produced by in-flight transfer or charge-exchange reactions. The system makes use of the velocity difference between the RIB beam of interest and the remaining tails of the primary beam after momentum selection by a bending magnet. The time-delayed primary beam components are deflected vertically out of the beam path by the RF sweeper, significantly reducing the stable beam background. Beam purity for the in-flight radioactive ion beams as high as 96% has been achieved with this system.