Speaker
Description
The ISIS rapid-cycling synchrotron (RCS) delivers high-intensity 800 MeV proton beams to two target stations at a repetition rate of 50 Hz. This operating regime necessitates low beam losses to minimise hardware activation. Beam losses at ISIS primarily arise from three mechanisms: transverse injection losses from foil recirculation hits, trapping losses due to coasting beam injection, and transverse losses during acceleration driven by space charge and the head-tail instability.
The ISIS pre-injector upgrade will commission several new components in the 70 MeV injector linac, with the addition of a MEBT section between the 665 keV RFQ and the first DTL tank forming the core of the upgrade. An electrostatic chopper, synchronised to the ring RF systems, will be installed in the MEBT primarily to eliminate trapping losses in the RCS by ensuring injection entirely within the acceptance of the ring RF. A potential additional benefit of the MEBT chopper is longitudinal phase-space painting, enabling favourable longitudinal distributions for mitigating transverse space-charge effects. Presented are simulations exploring this possibility, aimed at optimising longitudinal parameters to this end while satisfying the strict criterion of zero trapping loss.