Asymmetric B-factory project at KEK

The present machine design of the future asymmetric B‐factory at KEK is reviewed. Beam energies and a design luminosity are chosen as 8×3.5 GeV2 and 1×1034/cm2/sec in due consideration of requirements from physics experiments. In the design, it is aimed to squeeze the vertical beta‐function at IP (β*y) to 1 cm. The beam‐beam limit is assumed to be 0.05 with the requirement that the bunch length should be half of β*y, i.e., 0.5 cm. Flat beams are chosen. In order to attain the design luminosity, beam currents of 2.6 A for the 3.5 GeV ring and 1.1 A for the 8 GeV ring are necessary. An all RF buckets filling scheme and a crab crossing scheme are adopted to realize the short bunches and to decrease RF voltages. The damped cavity is adopted to suppress the coupled bunch instability. Growth rates of the instability are estimated in the case that the damped cavities are used. Further extensive studies and R&D’s are necessary to realize the design luminosity.