A precise measurement by AMS-02 of the electron spectrum up to 700 GeV and of the positron spectrum and positron fraction in primary cosmic rays up 500 GeV are presented. The combined measurement of the cosmic-ray electron and positron energy spectra and fraction provide a unique tool to improve our understanding of the production, acceleration and propagation mechanism of cosmic rays. AMS-02 detector The AMS-02 detector [2] consists of a permanent magnet, nine planes of precision silicon

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... r, a transition radiation detector (TRD), four planes of time-of-flight (TOF) counters, an array of anticoincidence counters, a ring imaging Cherenkov detector, and an electromagnetic calorimeter (ECAL). AMS-02 operates continuously on the ISS and is monitored and controlled around the clock from the ground. The timing, location, and attitude are determined by a combination of GPS units affixed to AMS-02 and to the ISS. The TRD (above the magnet), the ECAL (below the magnet) and the tracker provide clean and redundant identification of positrons and electrons with independent suppression of the proton background. The matching of the ECAL energy, E, and the momentum measured with the tracker, p, greatly improves the proton rejection. C The Authors, published by EDP Sciences. This is an Open Access article distributed under the terms of the Creative Commons Attribution License 4.0