Design status of LHeC LINAC-Ring interaction region

The ECFA-CERN-NuPECC design study for a Large Hadron electron Collider (LHeC) [1, 2] based on the LHC, considers two options, namely using a ring accelerator, similar to LEP, on top of the LHC or adding a recirculating energy-recovery linac tangential to the LHC. In order to obtain the required luminosity with an electron beam from a linac, with average lepton beam current limited to a few mA, reaching the smallest possible proton beam size is essential. Another constraint is imposed by the need to separate electron and proton beams after the collision without losing too much luminosity from a crossing angle. A further constraint is that the ep collision should occur simultaneously to pp collisions at other LHC interaction points such that the second LHC proton beam must be accommodated in the interaction region too. We present a conceptual layout using detectorintegrated combination-separation dipoles and challenging Nb$_{3}$Sn technology quadrupoles for focusing the colliding proton beam and providing a low-field hole to accommodate both the non-colliding proton beam and the lepton beam, and the optics for all three beams. We also discuss the optics design of the lepton final focus