LHeC Recirculator with Energy Recovery – Beam Optics Choices

High current, multi-ten-GeV operation of the electron recirculator for LHeC solely relies on the Energy Recovery (ER) process. A conceptual design of a 3-pass Recirculating Linear Accelerator (RLA) with ER is presented. It includes a complete multi-pass optics design for two superconducting linacs in ER mode and linear lattices for 6 return arcs. Synchronization between the arcs and linacs for chromatic beams requires very small values of momentum compaction. Furthermore, synchrotron radiation effects on emittance dilution (quantum excitation) are of paramount importance. To address both issues, here we propose a quasi isochronous arc optics design, which simultaneously ensures a small value of emittance dispersion, H, and therefore mitigates both transverse emittance growth and bunch length increase.