Commissioning of the PEP-II low-energy ring

The newly constructed PEP-II Low-Energy Ring (LER) is designed to store up to 3 A of 3.1 GeV positrons. It was built as a collaboration between SLAC, LBNL, and LLNL. The ring was completely installed and under vacuum on July 10, 1998. First stored beam was obtained on July 16, and first evidence for electron-positron collisions between LER and HER (High-Energy Ring) beams was observed on July 23, marking the formal completion of the PEP-II project. To date, three commissioning runs have occurred, the first in July 1998 (3 weeks), the second during October-December 1998 (7 weeks), and the most recent during January-February 1999 (5 weeks). During these runs various problems were uncovered and corrected, and the stored beam current has increased from 1 mA to 1160 mA. In this paper, the final LER configuration is described and results of the commissioning runs are presented. The LER is making steady progress toward its operating current of 2.16 A