The Alpha Magnetic Spectrometer (AMS) on the International Space

Station (ISS)

Maria Ionica

I.N.F.N. PerugiaMaria.Ionica@pg.infn.it

International School of Cosmic-Ray Astrophysics13th Course: Relativistic Astrophysics and Cosmology

2-14 June, 2002, Erice

Outline

Physics objectives of the AMS experiment AMS-01 on the space Shuttle Discovery in 1998 Results obtained with AMS-01 from the STS-91

flight The Silicon Tracker for the AMS-02 experiment on

the ISS

AMS - a particle physics experiment in space Existence of the matter-antimatter asymmetry in our region of the

Universe This asymmetry could be explained assuming one of the following

scenarios: The asymmetry is assumed as an initial condition The Universe can be globally symmetric, but locally asymmetric A dynamic mechanism which caused the asymmetry, starting from an

initial symmetric phase (CP violation, GUT) due to the limited energy which can be reached at accelerators, these

problems can only be studied by performing very accurate measurement of the composition of CR

The AMS experiment is using the Universe as the ultimate laboratory.

AMS physics goals To search for Nuclear Antimatter (antiHe,antiC) in space

with a 10-9 sensitivity (103 -104 better than current limits). To search for supersymmetric Dark Matter by high

statistics, precision measurements of e, and p- spectrum. To study Astrophysics:

High statistics, precision measurements of D, 3He, 4He, B, C, 9Be, 10Be spectrum

B/C: to understand CR propagation in the Galaxy (parameters of galactic wind).

10Be/9Be: to determine CR confinement time in the Galaxy.

Anti-nuclei in cosmic radiation

Researches for evidence of antimatter in CR have been carried out before AMS only by stratospheric balloons

If the antimatter exists it could be at the level of the clusters of galaxies

Anti-protons and positrons are not good indicators for existence of nuclear antimatter: they can be produced by the interaction of the primary cosmic rays with the interstellar medium;

The probability to have an antinucleus produced in primary interactions is less less than 10-10 for anti3He and less than 10-56 for antiC: “discovery of only one nucleus of antiC, would be the proof of the existence of antimatter in Universe”. (Steigman.G, Ann. Rev. Astron. Astrophys. 14 (1976)339)

AMS-01 on Discovery during STS-91 Flight

AMS01 detector

• Magnet: Nd2Fe14B, BL2= 0.15 TM2

• T.o.F: Four planes of scintillators;

and Z measurements, up/down separation

• Tracker: Six planes of ds silicon detectors;

• Charge sign, dE/dX up to Z=8, Rigidity (p/Z)

• Anticounters:

• Veto stray trajectories and bckgnd particles from magnet walls

• Aerogel Threshold Čerenkov:

measurements (13 GeV/c) for better e/p separation

• Low Energy Particle Shielding (LEPS):

• Carbon fibre, shield from low energy (<5MeV) particles

AMS deintegration at CERN: Silicon Tracker on assembly jig

AMS Silicon Detectors on the Automatic testing facilty (Perugia)

AMS silicon tracker module

AMS silicon tracker module

AMS Silicon Tracker plane equipped with Silicon Ladders (STS-91)

AMS-01- STS-91 Flight Results

It was a successful flight !!

Detector test in actual space conditions Good performance of all subsystems

Physics results: Antimatter search Charged cosmic ray spectra (p,e,D,He,C,N,O) Geomagnetic effects on cosmic ray

New limit on antiHe

Event reconstruction

Measure

Rigidity (R, R1, R2)Sign of RigidityAbsolute value of ZVelocity ()Apply cutsTest antiHe hypothesisCompute limit

AMS-01 STS-91 Flight Physics Results (1)

RESULTS on

Primary Cosmic Ray Spectra

58

Electron data

Energy Range of AMS on ISS

p+ up to several TeVp- up to 200 GeVe- up to O(TeV)e+ up to 200 GeVHe,….C up to several TeVanti – He…C up to O(TeV) up to 100 GeVLight Isotopes up to 20 GeV

AMS-02 Tracker (1) Coordinated by INFN Perugia in collaboration with University of

Geneva, University of Aachen, University of Turku and NLR. Aim:

Rigidity (P/Ze) measurements Sign of Charge Absolute Charge (dE/dX , in addition to ToF system)

Tracker detector based on 8 thin layers of double-sided silicon microstrips, with a spatial resolution better than 10 m, 200.000 electronics channel and 800 W of power.

This complex detector, qualified for operation in space, with about 6 m2 of active surface will be the largest ever built before the LHC @ CERN.

AMS-02 Tracker (2)

Operating Temperature: -10/+25 °C Power Dissipation inside the magnet: 1 W/ladder, in total

192 ladders dP/P = 2 % @ 1 GeV ( 8% in AMS-01) (for protons) The planes alignment will be monitored by a IR laser

alignment system (as in case of AMS-01).

AMS-02 Tracker (3)(from AMS-01)

Sensitivity of future CR experiments

Conclusions

AMS-01 has successfully been tested during STS-91 flight providing important information on operating in actual space conditions

AMS-01 data allows to study the primary and trapped CR fluxes in the energy range from 100 MeV to about 100 GeV

AMS-02 will extend the accurate measurements of CR spectra to unexplored TeV region opening a new window for the search for Antimatter and Darkmatter.

AMS-02 on ISS