RESUMO
The lattice design and beam dynamics optimization for Sirius, a new low-emittance synchrotron light source presently under construction at the Brazilian Synchrotron Light Laboratory (LNLS) in Campinas, Brazil, is presented. The electron storage ring is based on a five-bend achromat (5BA) design achieving a bare lattice emittance of 0.28â nmâ rad for a 3â GeV beam. The circumference of 518â m contains 20 achromatic straight sections of alternating 7â m and 6â m in length. An innovative approach is adopted to enhance the performance of the storage ring dipoles by combining low-field (0.58â T) magnets for the main beam deflection with a very short 2â T permanent-magnet superbend sandwiched in the center dipole. This superbend creates 12â keV critical photon energy dipole sources with modest total energy loss from dipoles. In addition it also creates a longitudinal dipole field gradient that reduces the emittance by about 10%. The optimized dynamic aperture allows for top-up operation with off-axis injection and the optimized energy acceptance allows for a total beam lifetime of around 11â h at nominal current with a third-harmonic cavity.