Filling pattern with non-uniform bunch spacing to mitigate e-cloud for the FCC-ee

The Future Circular Collider (FCC) study is developing designs for higher performance particle colliders that could follow on from the Large Hadron Collider once it reaches the end of its high-luminosity phase. In particular, the FCC-ee is a proposed electron-positron collider that may face challenges from the electron cloud (e-cloud). Specifically, the Z configuration foresees the highest number of bunches. Consequently, this configuration could suffer more form the deleterious effects of the e-cloud, such as transverse instabilities, transverse emittance growth, particle losses, vacuum degradation and additional heat loads on the inner surface of the vacuum chambers. The e-cloud effects have been observed in several circular accelerators all over the world and it is much more commonly in those operated with positively charged particles. Presently, it is among the major performance limitations for high energy collider. Therefore, the study of e-cloud mitigation techniques is crucial during the accelerator's design stage to suppress the e-cloud avalanche multiplication. This paper analyses the use of non-uniform bunch spacing patterns as a potential e-cloud mitigation strategy.