Synchrotron radiation in the interaction region for a Ring-Ring and Linac-Ring LHeC

The Large Hadron electron Collider (LHeC) aims at bringing hadron-lepton collisions to CERN with centre of mass energies in the TeV scale. The LHeC will utilise the existing LHC storage ring with the addition of a 60 GeV electron accelerator. The electron beam will be stored and accelerated in either a storage ring in the LHC tunnel (Ring-Ring) or a linac tangent to the LHC tunnel (Linac- Ring). Synchrotron Radiation (SR) in the Interaction Region (IR) of this machine requires an iterative design process in which luminosity is optimised while the SR is minimised. This process also requires attention to be given to the detector as the beam pipe must be designed such that disturbing effects, such as out-gassing and background scattering, are minimised while the tracker remains close to the IP thus maximising the acceptance of the experiment. The machinery of GEANT4 has been used to simulate the SR load in the IR and also to design absorbers/masks to shield SR from backscattering into the detector or propagating with the electron beam. The outcome of these simulations, as well as cross checks, are described in the accompanying paper which characterises the current status of the IR design for both the Ring-Ring and Linac-Ring options of the LHeC in terms of SR.