AMS-02 is a wide acceptance ( 0.5 m ^ { 2 } sr ) and long duration ( up to 20 years ) magnetic spectrometer operating onboard the International Space Station since May 2011 .
Its main scientific objectives are the indirect research of Dark Matter , searches of primitive Anti-Matter and the precise measurement of the Cosmic-Ray ( CR ) spectra .
Among charged CR species , AMS-02 will be able to measure relative abundances and absolute fluxes of CRs nuclei from Hydrogen up to at least Iron ( Z = 26 ) in a kinetic energy range from hundreds MeV to TeV per nucleon .
The high statistics measurement of the chemical composition of CRs in this extended energy range will reveal new insights about the CRs life in the Galaxy , from their origin to the propagation in the interstellar medium , giving new constraints to astrophysical models of Galactic CRs .
The nucleus absolute charge , Z , is measured several times along the trajectory of the particle inside AMS-02 using different detection techniques : in the 9 planes of the Silicon Tracker , in the 4 layers of scintillator counters of the Time-of-Flight system ( TOF ) , in the Ring Imaging Cherenkov Counter ( RICH ) as well as in the 20 layers of Transition Radiation Detector ( TRD ) and in the upper layers of the Electromagnetic Calorimeter ( ECAL ) .
The combination of the redundant measurements delivered by the tracking system and by the TOF allows an accurate discrimination between chemical elements .
The charge measurements in the detectors on top of AMS , as the Upper plane of the Tracker and in TRD , is used for the identification of the incoming nuclear specie and allows the charge-changing events background estimation .
The AMS-02 different charge measurement principles are here briefly explained , and performance of each sub-detector presented .
Then the AMS-02 combined charge separation capability as well as the interaction events identification principles are presented .