DESIGN OF POSITRON DAMPING RING FOR SUPER-KEKB

Super-KEKB, an upgrade plan of the present KEKB collider, has recently changed its baseline-design from “high current” option to “nano-beam” scheme. The current is relatively low(4A/2.3A for LER/HER ring) compared to that of the high-current option(9.4A/4.1A), while the vertical beam size is squeezed to 60 nm at the interaction point to get the high luminosity. Since the Tousheck lifetime of LER is very short(600 sec), the intensity of the positron beam is as high as 8 nC/pulse. The emittance of the injected positron beam should be small enough to be accepted in the aperture of the LER. A damping ring has been proposed for the high-current option[1]. In this paper an updated design optimized to the nano-beam scheme is presented.