The Alpha Magnetic Spectrometer (AMS) on the International Space Station (ISS)

1. The Alpha Magnetic Spectrometer (AMS) on the International Space Station (ISS) Maria Ionica I.N.F.N. Perugia Maria.Ionica@pg.infn.it International School of Cosmic-Ray Astrophysics 13th Course: Relativistic Astrophysics and Cosmology 2-14 June, 2002, Erice

2. 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

3. 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.

4. 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.

5. 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)

7. AMS-01 on Discovery during STS-91 Flight

8. 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 (13 GeV/c) for better e/p separation • Low Energy Particle Shielding (LEPS): • Carbon fibre, shield from low energy (<5MeV) particles

9. AMS deintegration at CERN: Silicon Tracker on assembly jig

10. AMS Silicon Detectors on the Automatic testing facilty (Perugia)

12. AMS silicon tracker module

13. AMS silicon tracker module

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

15. 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

16. New limit on antiHe

17. Event reconstruction Measure Rigidity (R, R1, R2) Sign of Rigidity Absolute value of Z Velocity (b) Apply cuts Test antiHe hypothesis Compute limit

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

20. RESULTS on Primary Cosmic Ray Spectra

27. Electron data

28. Energy Range of AMS on ISS p+ up to several TeV p- up to 200 GeV e- up to O(TeV) e+ up to 200 GeV He,….C up to several TeV anti – He…C up to O(TeV) g up to 100 GeV Light Isotopes up to 20 GeV

30. 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 mm,  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.

31. 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).

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

34. Sensitivity of future CR experiments

35. 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.

36. AMS-02 on ISS