ISIS is the pulsed muon and neutron source at RAL in the UK. Its operation centres on an 800 MeV rapid cycling synchrotron (RCS) running at 50 Hz, delivering 3×10¹³ protons per pulse and 0.2 MW average beam power to neutron targets. Current studies are aiming to improve the measurement, modelling, and control of ISIS ring beam dynamics, with the goal of optimizing operational setup and benchmarking beam loss studies for ISIS and the proposed MW upgrade, ISIS-II. This paper gives a brief overview of linear and non-linear longitudinal and transverse beam dynamics studies at ISIS, as well as beam measurement and modelling. The paper then focuses on non-linear beam dynamics studies in the low-intensity regime. Measured beam loss maps in tune space have been used to identify non-linear resonance lines. To better characterize individual resonance lines and improve the non-linear lattice model, comparisons are made between loss maps from experiment and results from extended particle tracking, Frequency Map Analysis (FMA) simulations, and analytical calculations. Detailed investigations of the third-order resonance lines 3Qx=13 and Qx+2Qy=12 are outlined.

The ISIS Rapid Cycling Synchrotron (RCS) operates at a repetition rate of 50 Hz and delivers high-intensity proton beams of up to $3\times10^{13}$ protons per pulse at 800 MeV to two neutron and one muon production targets. Maintaining control over the closed orbit is essential to optimal performance. Magnet alignment surveys are now regularly carried out during accelerator shutdowns, translated into misalignments, and applied to a cpymad model of the RCS. The model is used to identify realignment candidates and infer the bare (uncorrected) orbit. This paper includes comparison of inferred and measured bare orbits, and the operational implications of realignment based on the model. The approach demonstrates the value of integrating magnet alignment survey data with beam dynamics modelling to inform machine setup and improve operational performance in high-intensity synchrotrons.

ISIS is the pulsed muon and neutron source at RAL in the UK. Its operation centres on an 800 MeV RCS cycling at 50 Hz and providing up to 3E13 protons per pulse corresponding to 0.2 MW mean beam power to the user targets. Work is presently underway to improve the measurement, modelling, and control of the ISIS ring beam dynamics in order optimise operational setup as well as allow benchmarking of beam loss studies for the ISIS II upgrade. As part of this work, new measurements of linear stopbands are being established. This paper outlines measurement of half integer stopbands exploiting low intensity, coasting beams and measurements of beam loss and profiles as tunes are ramped through resonance. Measurements are tested against applied, known, driving terms and compared with PyORBIT simulations. Initial results looking at integer stopbands and extending work to high intensity half integer resonance are also outlined.