The LHC IR6 optics

The IR6 insertion houses the LHC beam dumping system. Large drift spaces are provided to accommodate the kicker and septum for the beam extraction and to minimise the strength of these components. This implies large values of the B-functions and associated constraints on the aperture of the components of the beam dump system. The design of these components has been made according to prelim inary versions of the LHC optics. Their characteristics have now to be taken as boundary conditions for the optics. Version 5 of the LHC optics was made with a new dispersion suppressor allowin g at least four different values of the tune-split. The possible variations of the phase advances of the insertion were exhaustively studied for the tunes {Qx=63, Qy=59} and checked for {Qx=66, Qy= 58}, the largest tune split up to now. The aperture constraints associated with the present design of the kicker and septum can be fulfilled. The old Q6 and Q7 are no longer needed, which makes a saving of 10 quadrupoles. The gradient requirements on the insertion and suppressor quadrupoles are given.