  AMS-02 is a wide acceptance (0.5 m2 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.
