Some small-emittance light-source lattices with multi-bend achromats

摘要

Two examples of low-emittance light-source lattices are discussed. Both use similar building blocks consisting of 7-bend achromats. The small emittances generated by these lattices are further reduced by the introduction of insertion devices (IDs), resulting in beam emittance values ranging from 0.2 to 0.9 nm rad, depending on the number of achromats chosen. The two examples discussed here are rings with 12 and 20 achromats. The performances of any intermediate number of achromats can easily be estimated. A higher number of achromats of this type seems to result in an uncomfortably small dynamic aperture. The Touschek losses and Intra Beam Scattering (IBS) effect are calculated together with some means to reduce their impact. To calculate this impact, certain technical solutions are assumed, which are described. Other technical solutions could naturally be chosen. The impact of emittance on brilliance is also discussed and the brilliance curves for the two cases are presented and compared with the zero-emittance case ("ultimate source").