Commissioning results of the KEKB and PEP-II B-factories

KEKB is a two ring asymmetric electron-positron collider at 3.5×8 GeV being built in the TRISTAN tunnel at the Japan National Laboratory for High Energy Physics KEK in Tsukuba. The five year KEKB construction project was approved by the Japanese government in April 1994. The parameters are listed and the overall layout of KEKB shown. The two beams will collide in the Tsukuba experimental hall where the BELLE detector will be located. The salient features of KEKB are side-by-side rings, +/- 11 mrad crossing angles at the collision point with non-radiating straight incoming beams, new RF cavities: Cu cavities with high stored energy (ARES) and superconducting cavities both designed to reduce the strength of the bunch-by-bunch feedback systems, many bunches (5000), high stored beam currents (2.6 A×1.1 A), superconducting IR quadrupoles, novel 2.5× lattice design for flexibility, and an upgraded linac for full energy injection of both beams with new transport lines. Beam commissioning started for the KEKB High Energy Ring HER in December 1998 and January 1999 for the Low Energy Ring LER. The present peak current in the LER is 380 mA and the HER 420 mA. A luminosity of 1.2×10**31/cm**2/s was achieved in March 1999 with 200 bunches with 13 mA×65 mA