Optics of a 1.5 TeV injector for the LHC

A concept is being developed to install a second, low energy ring (LER) above the LHC to accelerate protons from 450 GeV to 1.5 TeV prior to injection into the LHC. The arc and dispersion suppresser optics of the LHC would be replicated in the LER using combined function ''transmission line'' magnets originally proposed for the VLHC. To avoid costly civil construction, in the straight sections housing detectors at least, the LER and LHC must share beampipes and some magnets through the detector portion of the straights. Creating the appropriate optics for these LER-LHC transition regions is very challenging: In addition to matching to the nominal LHC lattice functions at these locations the changes in altitude of 1.35 m separating the LER and LHC must be performed achromatically to avoid emittance blowup arising from vertical dispersion when the beams are transferred to the LHC.