Refined tracking procedure for the SOLEIL energy acceptance calculation

In third generation light sources like SOLEIL, the inevitable strong sextupoles lead to significant non-linearities affecting the transverse beam dynamics. We already emphasized the large contribution of transverse and longitudinal non-linearities to the SOLEIL energy acceptance: energy dependence of Twiss parameters, non-linear off-momentum closed orbit and non-linear synchrotron motion. In order to face other effects as non-linear betatron motion, synchrotron oscillation, coupling, and diffusion processes, a refined tracking was performed using a 6D tracking code. This work confirms the strong effect of the non-linear synchrotron motion and suggests to choose the working point so as to avoid any crossing of the linear coupling resonance for off-momentum particles. The use of the Frequency Map Analysis (FMA) helps to understand the different kinds of particle losses.