• B.J. Holzer, S. Bettoni, O.S. Brüning, S. Russenschuck
  CERN, Geneva
• R. Appleby
  UMAN, Manchester
• J.B. Dainton, L.N.S. Thompson
  Cockcroft Institute, Warrington, Cheshire
• M. Klein
  The University of Liverpool, Liverpool
• A. Kling, B. Nagorny, U. Schneekloth
  DESY, Hamburg
• P. Kostka
  DESY Zeuthen, Zeuthen
• A. Polini
  INFN-Bologna, Bologna

The LHeC aims at colliding hadron-lepton beams with center of mass energies in the TeV scale. For this purpose the existing LHC storage ring is extended by a high energy electron accelerator in the energy range of 60 to 140 GeV. The electron beam will be accelerated and stored in a LEP like storage ring in the LHC tunnel. In this paper we present the layout of the interaction region which has to deliver at the same time well matched beam optics and an efficient separation of the electron and proton beams. In general the large momentum difference of the two colliding beams provides a very elegant way to solve this problem: A focusing scheme that leads to the required beam sizes of the electrons and protons is combined with an early but gentle beam separation to avoid parasitic beam encounters and still keep the synchrotron radiation level in the IR within reasonable limits. We present in this paper two versions of this concept: A high luminosity layout where the mini beta magnets are embedded into the detector design as well as an IR design that is optimised for maximum acceptance of the particle detector.

• F. Zimmermann, S. Bettoni, O.S. Brüning, B.J. Holzer, S. Russenschuck, D. Schulte, R. Tomás
  CERN, Geneva
• H. Aksakal
  N.U, Nigde
• R. Appleby
  UMAN, Manchester
• S. Chattopadhyay, M. Korostelev
  Cockcroft Institute, Warrington, Cheshire
• A.K. Çiftçi, R. Çiftçi, K. Zengin
  Ankara University, Faculty of Sciences, Tandogan/Ankara
• J.B. Dainton, M. Klein
  The University of Liverpool, Liverpool
• E. Eroglu, I. Tapan
  UU, Bursa
• P. Kostka
  DESY Zeuthen, Zeuthen
• V. Litvinenko
  BNL, Upton, Long Island, New York
• E. Paoloni
  University of Pisa and INFN, Pisa
• A. Polini
  INFN-Bologna, Bologna
• U. Schneekloth
  DESY, Hamburg
• M.K. Sullivan
  SLAC, Menlo Park, California

In a linac-ring electron-proton collider based on the LHC ("LR-LHeC"), the final focusing quadrupoles for the electron beam can be installed far from the collision point, as far away as the proton final triplet (e.g. 23 m) if not further, thanks to the small electron-beam emittance. The inner free space could either be fully donated to the particle-physics detector, or accommodate "slim" dipole magnets providing head-on collisions of electron and proton bunches. We present example layouts for either scenario considering electron beam energies of 60 and 140 GeV, and we discuss the optics for both proton and electron beams, the implied minimum beam-pipe dimensions, possible design parameters of the innermost proton and electron magnets, the corresponding detector acceptance, the synchrotron radiation power and its possible shielding or deflection, constraints from long-range beam-beam interactions as well as from the LHC proton-proton collision points and from the rest of the LHC ring, the passage of the second proton beam, and the minimum beta* for the colliding protons.