Correction of the Systematic b3 Error with the Resonance-Free Lattice in the LHC

The effect of the sextupole component b3 in the LHC dipoles on the resonance-free lattice has been investigated. It is shown that its dynamic aperture, without b3 spool piece correction, is close to that of the nominal LHC lattice version 6.0 with spool pice correction. A prerequisite is the addition of a few chromaticity sextupoles in the dispersion suppressors. Under this condition an increase of the b3 component by a factor of two can probably be accepted. Furthermore, a systematic relative gradient error up to one per mil can be tolerated without changing this result.