Cosmic Rays and Anti-Matter: The AMS Experiment

AMS-02 on the ISS
Fig. 1: AMS-02 on the ISS (Credits: NASA).

The Alpha Magnetic Spectrometer (AMS) is a high-energy particle physics experiment in space, designed to measure cosmic rays (CRs), i.e. energetic particles and completely ionized nuclei coming from outer space. The main purposes of the experiment are the indirect search of dark matter from its annihilation products, the search of relic anti-matter and the precise measurement of all CRs species spectra, and their variation in time, for the precise estimation of radiation doses for space exploration

In June 1998, the prototype of the experiment, the AMS-01 detector, flew on the space shuttle Discovery on the STS-91 mission, showing the feasibility of the AMS experiment. The design and construction of the final model of the experiment, the AMS-02 detector, took about 10 years and has been installed on the International Space Station (ISS) on the 19th of May 2011 during the space shuttle Endeavour STS-134 mission. AMS-02 is operating continuously since then, measuring the largest number of particles ever measured in space by a single experiment (>150 billion), and performing the most precise measurement of cosmic rays (CRs) to-date.

Luca Parmitano is installing the AMS-02 UTTPS.
Fig. 2: Luca Parmitano is installing the AMS-02 UTTPS (Credits: NASA).

Between November 2019 and January 2020, in a series of 4 complex extra-vehicular activities, Luca Parmitano (ESA) and Andrew Morgan (NASA) installed a new pump block for the cooling system of the AMS-02 Silicon Tracker. This operation effectively extended the lifetime of AMS-02 up to the entire duration of the ISS mission, up to at least 2028.

The AMS collaboration is composed of more than 500 scientists from more than 50 different institutions from 16 countries and is led by the Nobel Laureate Samuel C.C. Ting. The AMS Italian collaboration includes University and INFN Divisions of Bologna, Milano Bicocca, Perugia, Pisa, Roma, Roma Tor Vergata, and University and INFN center TIFPA of Trento. Thanks to the strong support of the Italian Space Agency (ASI), the Italian collaboration developed 3 of the main detectors of AMS (TOF, Silicon Tracker, and ECAL), and is at the core of the operations and data analysis of the experiment.

The AMS-02 Time of Flight system.
Fig. 3: The AMS-02 Time of Flight system, made in Bologna.

The AMS Bologna group built the Time-of-Flight system (TOF) of both AMS-01 and  AMS-02. The group has the full responsibility for its operations (monitoring, calibration, expert-on-call). The TOF has an important role in AMS, since it provides the main trigger of the experiment, measures the velocity and absolute charge magnitude of incident particles, and determines the particle direction (upward or downward) that is a key ingredient for the separation of matter from anti-matter.

The Bologna group is involved in the AMS data analysis, in the measurement of CRs nuclei fluxes, in their time variation, providing principal or cross-check analysis for the AMS publications.

The group is also active in the interpretation of CRs origin, acceleration, and propagation. This includes a long-term collaboration with GALPROP (Stanford) and HelMod (Milano Bicocca) groups, that are leading groups in the world for the modelization of CRs propagation in the Galaxy and in the Solar System respectively. This collaboration led to a series of publications about the most up-to-date phenomenologic model of CRs physics based on AMS-02 high precision data.

The AMS-02 Bologna group:

Andrea Contin,
Full Professor
Federico Palmonari,
Full Professor (Retired)
Alberto Oliva,
INFN Researcher
Nicolò Masi,
University Researcher
Lucio Quadrani,
University Technician
Giuliano Laurenti,
INFN Leader Technologist (Retired)   
Mauro Lolli,
INFN Technician
Cristina Guandalini,
INFN Technician

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