A first baseline for the layout of the High Luminosity inner triplet and associated magnets has recently been defined. This is the second major milestone, after the choice of a 150 mm aperture for the quadrupoles in July 2012.

A layout is the selection of the sequence of magnets, their strength, their length, and the associated technology: therefore, it requires inputs both from the optics and from the magnet teams. Its definition is a delicate equilibrium between the search for maximum performance and the need of minimizing complexity and associated risks. Nb₃Sn technology had been already selected for the triplet quadrupoles – these magnets are planned to be built with a CERN-US collaboration, heavily relying on the worked carried out by LARP in the past 10 years. After the triplet, a separation dipole of 5.5 T, in Nb-Ti, is being studied by the Japanese team in KEK. 

The layout is complemented by the challenging orbit correctors, also based on Nb-Ti technology, with nested coils both providing horizontal and vertical field of up to 2 T. A package of higher order correctors relying on superferric technology is also available, in order to correct for the inevitable field imperfections of the inner triplet at the 10-4 level The triplet corrector package is based on the design developed in Spain by CIEMAT. As a result, the energy deposition team can start simulations to have a precise estimate of the radiation damage and heat loads coming from the collision debris. It is a heavy shower and magnets will need thick shielding to avoid falling in pieces before reaching the project ambitious goal of 3000 fb^-1. The layout has been presented at CERN and will be extensively discussed at the HiLumi/LARP collaboration meeting, 8-10 April 2013, Napa Valley in the US.

The LHC baseline as installed in the tunnel today (Image: HL-LHC)