The international AMS (Alpha Magnetic Spectrometer) experiment to be installed on the International Space Station in 2006 is designed to study Cosmic Rays and it will largely extend the knowledge of its spectrum, in terms of nuclei, isotope and particle/antiparticle relative fluxes.

  AMS is a large angular acceptance spectrometer composed of different subdetectors to provide particle identification capabilities. In particular, the presence of a RICH (Ring Imaging CHerenkov) detector, provides AMS with a capability of making accurate measurements of electric charge and velocity.

  The RICH is composed of a radiator material (aerogel) on the top, a matrix of 680 multianode photomultipliers at the bottom and a large conical mirror around for increasing the detector geometrical acceptance.

  When a charged particle crosses the radiator with a speed greater than the speed of light in that medium, Cherenkov photons (strongly in UV) are emitted along a cone with an aperture angle related to the charged particle's velocity. The geometrical pattern produced by the detected photons together with the hit produced by the light guide particle crossing was used to develop a RICH algorithm for determining the particle direction - polar and azimuthal angles - and Cherenkov angle.