Accelerator design at SuperKEKB

The SuperKEKB project requires a positron and electron collider with a peak luminosity of 8 x 10(35) cm(-2) s(-1). This luminosity is 40 times that of the KEKB B-factory, which operated for 11 years up to 2010. SuperKEKB is an asymmetry-energy and double-ring collider; the beam energy of the positron (LER) is 4 GeV and that of the electron (HER) is 7 GeV. An extremely small beta function at the interaction point (IP) and a low emittance are necessary. In addition, in order to achieve the target luminosity, a large horizontal crossing angle between two colliding beams is adopted, as is a bunch length much longer than the beta function at the IP. This method is called the nano-beam scheme. The beam-beam parameter is assumed to be similar to KEKB, the beta function at the IP is 1/20, and the beam currents are twice those of KEKB in the nano-beam scheme. Consequently, the luminosity gain of 40 with respect to KEKB can be obtained.