Design Considerations for an Ultralow Emittance Storage Ring for the Canadian Light Source

Demands from light source scientists for more brilliant xray beams have resulted in the emergence of 4th generation storage rings. These demands include photon beams that are highly focussed and beams with high transverse coherence. Both these requirements are achieved with ultralow electron beam emittance. The practical development of the multi-bend achromat (MBA) concept by MAX IV has spurred many synchrotron light sources around the world to develop similar machines. For existing facilities two options are available: upgrading existing machines or building a new structure. The Canadian Light Source (CLS) has explored both options and has determined a new storage ring is required. Several design options for a 3.0 GeV ring have been developed. Best results are achieved when tracking is used to optimize the phase advance through the MBA structure to reduce the impact of the sextupoles on the dynamic aperture. Structures where no geometric sextupoles are required have been achieved while producing ultralow emittances.