Status of the PEP-II B-factory

PEP-II is a two ring asymmetric electron-positron collider at 3.1 x 9.0 GeV being built in the PEP tunnel at the Stanford Linear Accelerator Center SLAC. The five year PEP-II construction project was approved by the Department of Energy of the United States government in January 1994. A collaboration of SLAC, Lawrence Berkeley National Laboratory LBNL, and Lawrence Livermore National Laboratory LLNL designed and constructed PEP-II. The overall layout of PEP-II is shown in Figure 1 and the accelerator parameters are listed in Table 1. The beams collide in the IR2 hall of the PEP tunnel where the BaBar detector is located. The salient features of PEP-II are LER-above-the-HER, head-on collisions but with dipoles bends near the collision point, new copper RF cavities, strong bunch-by-bunch feedback systems, many bunches (1658), high stored charges (2.1 A x 0.75 A), permanent magnet IR quadrupoles and dipoles, and use of the existing SLAC linac as an injector but with new transport lines. PEP-II HER commissioning started in June 1997 and LER commissioning in July 1998. The present maximum current in the HER is 750 mA in 1658 bunches which is the design value. The LER has stored 1551 mA, which is believed to be a world record for a positron ring. A luminosity of 1.35 x 1033/cm2/s was achieved in September 1999 with 830 bunches with 610 mA x 960 mA (HER x LER), which is also a world's record. A peak daily integrated luminosity of 64.3 pb-1 has been delivered to BaBar of which BaBar has logged 57.8 pb-1. A total of about 1.5 fb-1 has been delivered by PEP-II to BaBar by the end of September 1999. (author)