Interaction of intrabeam scattering, longitudinal wakefield, and a passive harmonic RF cavity in SOLEIL II

Synchrotron light sources worldwide are transforming into next-generation facilities with ultralow transverse emittances at the diffraction limits. With these parameters, intrabeam scattering (IBS) becomes significant and can spoil the light quality by increasing emittance. A harmonic cavity can be installed to mitigate this effect by increasing the bunch length. Another way to reduce the impact of IBS is to operate with the full transverse coupling. This contribution considers the IBS effect on SOLEIL II performance with an up-to-date impedance model, passive harmonic cavity, different insertion device gap configurations (open, close), and full transverse coupling for all foreseen operation modes. The combined effect of IBS and microwave instability (MWI) on the energy spread is reported. It is demonstrated that the contribution of IBS to energy spread increase is as important as that of MWI.