Empirical tests and model of a silica aerogel Cherenkov detector for CEBAF

A prototype of a silica aerogel Cherenkov detector to be used for pion-proton discrimination in one of the HRS spectrometers of CEBAF Hall A has been built and tested. Each detector housing is made of carbon fiber composites and incorporates planar parabolic mirrors. The prototype was tested in electron and pion beams. The detection efficiency for particles well above the Cherenkov emission threshold has been measured to be greater than 99%, and the false trigger rate was measured to be less than 3x10-2. The results are consistent with a Monte Carlo simulation of the prototype detector, indicating that the performance of the detector is well understood. (orig.)