  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.
