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ISIS is the spallation neutron source at the Rutherford Appleton Laboratory in the UK. Operation centres on an 800 MeV rapid cycling synchrotron (RCS), which provides 3×1013protons per pulse (ppp) at 50 Hz, corresponding to a beam power of 0.2 MW. In common with many lower energy, high intensity proton rings, a key loss mechanism on ISIS is half integer resonance under space charge. This paper summarises experimental and simulation work studying half integer resonance in a "2D" coasting beam in the ISIS ring: understanding this is an essential prerequisite for explaining the more complicated case of RCS operation. For coasting beam experiments, the ring is reconfigured to storage ring mode with RF off and main magnets powered on DC current only. A 70 MeV beam is injected, painted appropriately, and manipulated so as to approach resonance. Understanding how the resonant condition develops is central to explaining observations, so realistic simulations of resonance, including injection, ramping of intensity and tunes are being developed. Results from the ORBIT code are presented and compared with experimental and theoretical results. Finally, future plans are summarised. Copyright © 2011 by IPAC'11/EPS-AG.


Conference paper

Publication Date



637 - 639