Problems and Considerations about the Injection Philosophy and Timing Structure for CEPC

This paper describes the injection philosophy and the design of timing and filling scheme for the high luminosity Circular Electron and Positron Collider (CEPC) scheme under different energy modes. It is found that the RF frequency choice in Conceptual Design Report (CDR) cannot meet the injection requirements for the bunch number at the Z pole. A modified scheme was proposed to support the design luminosity, which basically meets our current design requirements and retains more flexibility for a future high-luminosity upgrade.