In-beam aerogel light yield characterization for the AMS RICH detector

The ring imaging Cherenkov (RICH) detector of the AMS-02 spectrometer provides a very precise measurement of the electric charge and velocity. The RICH detector is composed of a conical reflector ended on top by a dual radiator plane made of sodium fluoride and aerogel, and at the bottom by a detector plane made of pixelized photomultipliers. The vast majority of the events (∼90%∼90%) that are collected in the RICH cross the aerogel radiator. Therefore, the choice and characterization of the aerogel radiator is essential for reaching the design goals. A prototype of the RICH detector was built for both concept proof and testing of the different elements. Beam tests with the RICH prototype and using several aerogel radiator samples were performed at CERN in 2002 and 2003. This note summarizes the method used and the results obtained for the light yield of different aerogel samples.