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TY - CONF AU - Pine, B.G. AU - Warsop, C.M. ED - Koscielniak, Shane ED - Satogata, Todd ED - Schaa, Volker RW ED - Thomson, Jana TI - High Order Image Terms and Harmonic Closed Orbits at the ISIS Synchrotron J2 - Proc. of IPAC2018, Vancouver, BC, Canada, April 29-May 4, 2018 C1 - Vancouver, BC, Canada T2 - International Particle Accelerator Conference T3 - 9 LA - english AB - ISIS is the spallation neutron source at Rutherford Appleton Laboratory in the UK. Protons are accelerated from 70 to 800 MeV in a 50 Hz rapid cycling synchrotron. Due to the intense beam, space charge forces are high during the first part of the acceleration cycle. The vacuum vessel in the synchrotron has a rectangular shape where the apertures are conformal to the design beam envelopes. At high intensities image forces interact with the beam, especially when the closed orbit is large. An analysis of image forces has been made and used to classify higher order image terms. These have been identified using simulations of round beams in rectangular vacuum vessels. The higher order image terms from harmonic closed orbits have been used with single particle resonance theory, taking account of the coherent nature of the beam response. Several predictions of beam resonance have been made. A simulation study has been carried out using a smooth focusing lattice and uniform density beams. Resonant beam behaviour has been observed and explained by the proposed theory. PB - JACoW Publishing CP - Geneva, Switzerland SP - 1140 EP - 1143 KW - closed-orbit KW - simulation KW - resonance KW - space-charge KW - vacuum DA - 2018/06 PY - 2018 SN - 978-3-95450-184-7 DO - 10.18429/JACoW-IPAC2018-TUPAL056 UR - http://jacow.org/ipac2018/papers/tupal056.pdf ER -