Design Considerations for the CLIC pre-damping rings

The CLIC pre-damping rings (PDR) have to accommodate a large emittance beam, coming in particular from the positron target and reduce its size to low enough values for injection into the main damping rings (DR). The lattice design is based on theoretical minimum emittance (TME) arc cells and long straight sections filled with damping wigglers. Lattice design optimisation considerations are presented with emphasis to the linear optics functions, tunability, chromatic properties and acceptance. A complete phase advance scan of the TME cells is undertaken for reducing the non-linear resonance driving terms and amplitude dependent tunespread and maximizing the ring’s dynamic aperture (DA).