C. Goy

The Electromagnetic Calorimeter Trigger System for the AMS-02 Experiment

AMS-02 is an astroparticle experiment designed for a very precise measurement of the primary cosmic rays spectrum. The experiment will operate on board the ISS at a 400 km altitude for a period of about 3 years. The main scientific goals of the experiment are the search for antimatter, for dark matter and the study of gamma rays. In AMS-02 the electromagnetic calorimeter plays a key role for its high capability to measure e+, e- and gamma spectra and to suppress the background generated by p and He nuclei. To directly detect photons the calorimeter must provide a stand alone trigger. The proposed trigger, presented in this article, will have the capability to detect photons with energy above 4 GeV with an efficiency of about 100%. The hardware implementation comprises an analog section, comparing the photomultiplier signal with a given threshold, and a digital section applying the trigger selection algorithm.

ELECTROMAGNETIC CALORIMETER FOR THE AMS-02 EXPERIMENT

The electromagnetic calorimeter (ECAL) of the AMS-02 experiment is a 3-dimensional sampling calorimeter, made of lead and scintillating fibers. The detector allows for a high granularity, with 18 samplings in the longitudinal direction, and 72 sampling in the lateral direction. The ECAL primary goal is to measure the energy of cosmic rays up to few TeV, however, thanks to the fine grained structure, it can also provide the separation of positrons from protons, in the GeV to TeV region. A direct measurement of high energy photons with accurate energy and direction determination can also be provided.