Design and test results of the AMS RICH detector

The AMS-02 detector will operate for at least 3 years on the International Space Station, measuring cosmic ray spectra at about 400 km above sea level over a wide range of geomagnetic latitude. The proximity focusing ring imaging \v{C}erenkov counter of AMS-02 will measure the particle velocity $\beta$ with $\approx 0.1$ uncertainty, making possible to discriminate Beryllium isotopes up to about 15 GeV/nucl. In addition its charge measurement will allow to study the elemental composition of cosmic rays up to Iron. A prototype of the RICH detector was tested with cosmic rays and on a ion beam accelerated by SPS, at CERN (October 2002).