The Focusing Detector of Internally Reflected Cherenkov light (FDIRC) has been designed to separate efficiently kaons from pions up to a few GeV/c in the barrel region of a HEP experiment. This ring-imaging Cherenkov detector is based on the same principle as the BABAR DIRC, which was successfully operated at the SLAC PEP-II asymmetric B-Factory during a decade. Charged particles cross thin quartz bars in which they radiate Cherenkov light; part of these photons are trapped in the radiators by total internal reflection and propagate until a camera where they are detected by photon detectors. The FDIRC was intended for the SuperB detector, a new generation flavour factory which has been cancelled at the end of 2012 due to lack of funding. Therefore, it has been designed to be able to operate at very high luminosity (10^36/cm^2/s) and large backgrounds. This led to a complete redesign of the photon camera: the huge tank of ultra-pure water used for the BABAR DIRC has been replaced by much smaller focusing cameras with sophisticated solid fused silica optics. Indeed, the BABAR camera was sensitive to background and its operation required constant attention to avoid any water leak inside the rest of the detector. The new cameras are instrumented with highly-pixelated Hamamatsu H-8500 MaPMTs, readout by new fast front-end digitizing electronics. The goal is to have a detection chain about 10 times faster than in BABAR, allowing the FDIRC to reject more background hits and to measure Cherenkov angles more accurately. A full-scale prototype of a FDIRC sector (1/12th of the whole detector) has been successfully built at SLAC and is taking data in the Cosmic Ray Telescope facility since the beginning of 2013. The primary goals of this R&D program are to validate the innovative camera design, to test the full detection chain and to measure the FDIRC Cherenkov angle resolution.
The Focusing Detector of Internally Reflected Cherenkov Light (FDIRC) for Charged Particle Identification