Injection optimisation on the ISIS synchrotron

The ISIS Facility at the Rutherford Appleton Laboratory in the UK produces intense neutron and muon beams for condensed matter research. It is based on a 50 Hz proton synchrotron which, as the commissioning of a new dual harmonic RF system concludes, will accelerate up to 3.75×1013 protons per pulse from 70 to 800 MeV, delivering a mean beam power of 0.24 MW. The multi-turn charge-exchange injection process strongly affects transverse beam distributions, space charge forces and thus beam loss, which ultimately limits operational intensity. Optimising injection is therefore a key consideration for present and future upgrades. This paper summarises injection studies including 2D space-charge simulations of the ISIS injection process using the ORBIT code [1]. Comparisons of simulation results with measurements for a range of beam intensities are presented and an assessment is made of a correlated painting scheme in contrast to the usual anti-correlated configuration. Previous simulation work has suggested this may result in a more uniform beam distribution in vertical phase space [2].