DIRC, the internally reflecting ring imaging Cherenkov detector for BABAR

The DIRC is a new type of Cherenkov imaging device that will be used for the first time in the BaBar detector at the asymmetric B-factory, PEP-II. It is based on total internal reflection and uses long, rectangular bars made from synthetic fused silica as Cherenkov radiator and light guide. The principles of the DIRC ring imaging Cherenkov technique are explained and results from the prototype program are presented. Its choice for the BaBar detector particle identification system is motivated, followed by a discussion of the quartz radiator properties and the detector design.