LHeC ERL Design and Beam-dynamics Issues

We discuss machine and beam parameter choices for a Linac-Ring option of the Large Hadron electron Collider (LHeC) based on the LHC [1]. With the total wall-plug power limited to 100 MW and a target current of about 6 mA the desired luminosity of 1033 cm-2s-1 can be reached, providing one exploits unique features of the Energy Recovery Linac (ERL). We describe the overall layout of such ERL complex located on the LHC site. Multi-pass linac optics enabling operation of the proposed 3-pass Recirculating Linear Accelerator (RLA) in the Energy Recovery mode is presented. We also describe emittance preserving return arc optics architecture; including layout and optics of the arc switchyard. Furthermore, we discuss importance of collective effects such as multi-pass beam breakup instability (BBU) in ERL.