The SLS booster is composed of a FODO-like lattice, made mainly of two families of combined-function magnets [2]. The first one has horizontal-focusing and a low bending field (large bending radius). The second family has horizontal-defocusing with larger bending field (small bending radius). Each family has an integrated sextupole component on it, used to compensate the chromaticity near the desired values of (1,1). Additional families of quadrupoles and sextupoles are used to adjust the working point and to the fine adjustment of the chromaticity.
The repetition rate of the SLS booster is 3 Hz . It allows a reasonably fast filling of the SLS storage ring and gives the beam time to damp down to the equilibrium emittance, while allows a simple vacuum chamber design [3].
The existence of two different kind of bending magnets (with different bending radius) is one of the differences with respect to other machines, giving two different contributions to the sextupolar field generated by the eddy currents during ramping. The other difference with respect to conventional boosters is that the bending magnets have already a sextupolar component that brings the chromaticity to positive values.That would make the effect of the sextupolar field generated by eddy currents less important than in other more conventional boosters.
We are going to concentrate in the effect of the sextupole components generated in the bending magnets vacuum chamber. Other contributions, like eddy currents in the quadrupoles, or higher order multipolar terms in the dipoles are much smaller and can be safetely neglected. The other major effect of the eddy currents is a heating of the vacuum chamber. However, due to the low field, the small vacuum chamber with thin walls and the low repetition rate, the power dissipated is very small (about 0.1 W/m), and the heating of the vacuum chamber negligible.
The main parameters of the booster are summarized in Table 1 and the optical functions for 1/6th of the booster (half superperiod) are show in figure 1.
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