Optimising Multi-turn extraction at CERN using transverse feedback

Abstract Initial experimental investigations of transverse beam splitting, carried out at the CERN Proton Synchrotron, have demonstrated that transverse feedback is highly effective in controlling the characteristics of the split beam. The feedback notably improves the intensity distribution among the beamlets and the emittance of the core, which is the portion of the beam that remains near its centre after the resonance-crossing process. The transverse feedback is set in resonance with the horizontal betatron tune while the tune crosses the 4 th -order resonance, creating a double-resonance condition. A simple Hamiltonian model has been used to explore the underlying double-resonance mechanism. This paper thoroughly examines detailed numerical simulations based on a realistic lattice model alongside beam measurements, to identify optimisation strategies for the use of transverse feedback in controlling the properties of split beams.