Operational experience with the DIRC detector

The DIRC, a novel type of Cherenkov ring imaging device, is the primary hadronic particle identification system for the BABAR detector at the asymmetric B-factory, PEP-II at the Stanford Linear Accelerator Center. It is based on total internal reflection and uses long, rectangular bars made from synthetic fused silica as Cherenkov radiators and light guides. BABAR began taking data with colliding beams in late spring 1999. This paper describes the performance of the DIRC during the first 2.5 years of operation.