The Swap-Out Injection Scheme for the High Energy Photon Source

The on-axis swap-out scheme is a promising injection scheme for di raction-limited storage rings, since it only re- quires a rather small dynamic aperture and thus potentially allows a higher brightness compared to traditional o -axis injection schemes. However, a full charge injector is neces- sary for this scheme and its design can be nontrivial, in par- ticular to satisfy the large single bunch charge requirements in special lling patterns for timing experiments. In the High Energy Photon Source, we propose using the booster also as a high energy accumulator ring to recapture the spent bunches extracted from the storage ring, so as to relax the challenges in generation and acceleration of bunches with a high charge, and as a cost-e ective solution compared to building a dedicated full energy accumulator ring. In this paper, the beam dynamics issues of this scheme will be presented, trade-o s between the storage ring and booster beam parameters and hardware specifications will also be discussed.