• C.M. Warsop, D.J. Adams, B. Jones, S.J. Payne, B.G. Pine, R.E. Williamson
  STFC/RAL/ISIS, Chilton, Didcot, Oxon

ISIS is the spallation neutron source at the Rutherford Appleton Laboratory in the UK. Operation centres on a 50 Hz proton synchrotron, which accelerates ~3·10¹³ ppp from 70 to 800 MeV, corresponding to beam powers of 0.2 MW. Beam loss imposes limits on operational intensity, and a main contributing mechanism is the action of half integer resonance under high space charge. The same loss mechanism is also a potential problem in ISIS upgrade scenarios involving either higher energy injection into the existing ring, or the addition of a new 3 GeV, high intensity RCS. Progress on particle in cell simulation studies investigating the effects of the driven coherent envelope motion, the associated parametric halo, along with implications of momentum spread, dispersion and longitudinal motion, is reported. Where possible, comparisons are made with relevant theoretical models. Closely related benchmarking work, experimental studies and plans are also summarised.