Studies on sextupole components generated by eddy currents in the Rapid Cycling Medical Synchrotron

The Rapid Cycling Medical Synchrotron is a second generation medical accelerator that it has been designed with a repetition frequency of 30 Hz. This repetition frequency is far above the typical repetition frequency used in medical accelerators. An elliptical beam pipe has been chosen for the RCMS design in order to win as much physical aperture as possible while keeping the magnet dimensions as small as possible. Rapid Cycling induces Eddy current in the magnets. Eddy currents and elliptical beam pipes generate sextupole components that might be necessary to consider. In this paper, the effects of these sextupoles components are evaluated, first by looking at the phase space of a bunch of particles that has been tracked for 62530 turns, and also by evaluating the dynamical aperture of the accelerator. The effect of the sextupoles component in the tuneshift is also evaluated. First results obtained with Marylie show that the width of a phase space ellipse of a bunch of particles is slightly affected by the sextupoles due to the Eddy currents.