The Alpha Magnetic
Spectrometer on the
International Space Station
Carmen Palomares
CIEMAT (Madrid)
On behalf of the AMS Collaboration
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AMS is a magnetic spectrometer to be installed on ISS ( 450 km)
The aim of AMS is the direct detection of primary cosmic rays
below the knee (NO UHECR):
Determination of energy with high resolution
Large
statistics
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Very good particle identification
AMS-02
 Large geometrical acceptance: 0.45 m2 sr
 Long exposure: 3 years
 Redundant measurements of the main
parameters
Operational conditions:
 High vacuum
 High radiation levels
 Strong gradients of temperature :
-60°C — +40°C
 Weight < 7 Tons
 Acceleration 3g (6g) launch (landing)
 Power consumption < 3 kW
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AMS Goals
Antimatter search (He) with a
sensitivity 103 better than
current limits
Dark matter search.
Non-baryonic DM: WIMP (LSP)
Signatures: e+, p
 High statistics study of
the cosmic ray spectrum
 Isotope separation
 Antiparticle spectrum
1 year
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AMS detector
Set of sub detectors devoted to the measurement of energy and
particle identification: Z, mass,…
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AMS detector
Energy ( R , p )
Tracker
(R)/R = 1.5% for 10 GV
Max. Dynamic Range 1 TV
ECAL
(E)/E ~ 3%
for 100 GeV electrons
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AMS detector
Particle Identification
Charge (Z): Tracker, ToF and RICH
Z  26 (small charge confusion)
Tracker + ToF  sing(Z)
Electron/hadron separation:
TRD: p/e rejection factor 102 - 103
in the range 1.5 – 300 GeV
ECAL: Hadron rejection factor 104
for E<1TeV
Test-beam results
 (Mass) :
ToF: ()/ = 3.5% (for =1)
RICH: ()/ ~ 0.1% for protons
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AMS detector status
The sub-detectors have been tested:
 Test-beams at CERN using prototypes of the final detectors
 Qualification tests of the flight elements
Currently, they are being assembled and qualified
Integration and functional tests of the whole detector at CERN (2006)
Magnet: coils already done
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Galactic Cosmic Rays
The high energy CR are produced, accelerated and
propagated in the Galaxy and provide information about
the sources and the matter content and magnetohydrodynamical properties of our Galaxy
Current critical measurements that can be achieved by AMS are:
• Very accuracy measurements of the spectrum of H & He (R 1 TV)
• Chemical abundances (from H to Fe)
• The ratio of spallation products such as Boron to the primary nuclei
such as Carbon as a function of energy (E  1 TeV)
• The energy dependence of the fraction of antiparticles (E100GeV)
• Isotopic ratios of elements (E  10 GV)
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Energy Spectrum
Protons and Helium:
The most abundant elements
Spectral index: Origin and acceleration, differences
between both species
Used to determine the expected fluxes of p and e+ ,
atmospheric neutrinos, etc…
protons
AMS-02
expectations
Helium
AMS-02
expectations
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Hadrons Z>2
In addition to the information provided by primary CR such
as C, N and O, secondary CR (produced by spallation) are
used to estimate the amount of matter traversed by the CR
(confinement volume and time)
AMS-02
expectations
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Radiactive Isotopes:
Provide information about the confinement
time of CR in the Galaxy
10Be
is specially interesting for
its half time (t1/2 = 1.51 106 years)
of the same order than the
confinement time of the CR in the
Galaxy
AMS-02
expectations
 After 3 years, AMS will collect
~105 10Be
 (m)/m = 2%
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Antiparticles
Pure secondary CR from interactions with the ISM
Exotic origin: A very good understanding of the expected CR fluxes
Antiprotons
Positrons
Data consistent with secondary CR
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No conclusive data
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Antiparticles
AMS will measure the
p
flux up
to 400 GeV
After 3 years will collect 106
p
AMS will collect 106 e+ and 107 eThese fluxes provide sensitivity to dark
matter in several scenarios
AMS-02
expectations
AMS-02
expectations
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Summary
• AMS will be the first large acceptance magnetic spectrometer
to operate in space for a long period of time
• Precise experimental measurements provided by AMS would
yield information about the galactic properties, constraining
propagation models
• AMS will be able also to discover some evidence for new
physics (dark matter) or new objects (e.g. stars made of
antimatter)
• Currently, AMS-02 is in the construction phase.
The detector must be ready for the launch by the end of 2007
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More Slides
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Light Isotopes
D and 3He are secondary particles coming from nuclear
interactions with the ISM and provide a description of the
propagation of p and He
6 hours
1 day
AMS-02
expectations
AMS-02
expectations
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Search of antimatter
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•Good understanding of GCR origin and
propagation will be used to discover some
evidence for new physics (dark matter) or new
objects (e.g. stars made of antimatter)
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ECAL
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Ring Imaging Cerenkov Detector
Radiator (aerogel)
()/ ~ 0.1% para =1
Charge determination up to Z~26
mirror
PMT Plane
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Transition Radiation Detector
20 layers
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