Increasing the energy acceptance of high brightness synchrotron light storage rings

Brightness is the prominent figure of merit for the present third-generation synchrotron light sources. The associated high electron density leads to beam lifetime reduction due to the “Touschek effect”, especially in low-energy machines and in the single-bunch operation mode. For this reason, several low-energy third-generation light sources cannot fully exploit their potential to increase brightness by lowering the coupling between vertical and horizontal emittance without arriving at unacceptably short beam lifetime. ouschek lifetime” can be increased if the energy acceptance of the synchrotron light storage rings could be widened beyond the usual value of ± 2% which is normally provided in order to satisfy quantum lifetime requirements. The present article describes the lattice and RF system proposed for the Swiss Light Source project (SLS) that have been further optimized in order to provide energy acceptance of about ± 6%. The increased energy acceptance might also be of interest for high-gain storage-ring-based FEL applications.