Design optimisation for the CLIC damping rings

The CLIC damping rings should produce the ultra-low emittance with high bunch charge necessary for the luminosity performance of the collider. This large bunch density triggers a number of beam dynamics and technical challenges. Lattice studies have been focused on low emittance cells with optics that reduce Intra-beam scattering. Collective effects such as electron cloud and fast ion instability can severely limit the performance and mitigation techniques have been identified and tested. The final beam emittance is reached with the help of superconducting damping wigglers. Results from recent simulations and prototype measurements are presented, including an absorption scheme design. Tolerances for alignment and technical system design such as kickers, RF cavities, magnets and vacuum have been finally established.