Sirius’ Storage Ring uses a 20-cell 5BA magnetic lattice to achieve a very low beam emittance of 0.25 nm.rad. The 518 m circumference contains 20 dispersion-free straight sections of alternating 6.5 and 7.5 meters in length, to be used for insertion devices as well as injection and RF systems. The central dipole of the 5BA cell is a permanent magnet with transverse and longitudinal field gradients to reduce the emittance and provide a hard X-ray radiation source. The thin high field section at its center of approximately 3.2 T provides radiation with critical energy of 19 keV with a modest contribution to the total energy loss. The other low field dipoles (0.58 T), responsible for the main beam deflection, will be electromagnetic.

The Booster lattice consists of 50 modified FODO cells with combined-function magnets suitable to provide low emittance. The main difference from other booster designs is that the Sirius booster contains only arc sections: no long dispersion-free straight sections are provided. This means that injection and extraction, as well as the Petra 5-cell RF cavity, are located in these dispersive straight sections. With this concept a very high lattice symmetry for the booster is obtained and only a few magnet families are necessary.