LHC IR Upgrade: A Dipole First Option with Local Chromaticity Correction

In the framework of the LHC Luminosity Upgrade, we develop a new layout of the interaction region (IR) with <font face="Symbol">b</font>* equal to 25cm in which the combination-separation dipoles come first with respect to the triplet assembly (dipole first) in opposition of the nominal layout (quadrupole first). The new layout presents several advantages (separate channel for multipole error correction, straightforward crossing angle scheme with no crossing in the triplet, early separation of the beam). The payoff is a large <font face="Symbol">b</font>* function in the triplet, which enhances the chromaticity, non-linear effects and eats up aperture. We investigate options for local chromaticity correction and their effects on long-term stability.