The AMS Transition Radiation Detector and the Search for Dark Matter
Gianpaolo Carosi Lab for Nuclear Science, MIT The AMS Collaboration Lake Louise Winter Institute 2/23/05
Outline• Signatures of dark matter in cosmic rays
• Overview of the AMS-02 detector
• Principles of Transition Radiation
• Construction of the AMS TRD system
• Physics reach of AMS-02 detector with the TRD
The Problem of Dark Matter• What is it?
-Matter which appears to not interact electromagnetically.
-Observed from gravitational interactions only!
v2
v1
Galactic Rotation Curves
R1
R2
R2R1
v1 v2
00 SUSY Dark Matter
• Neutralino – majorana particles
Direct searches: Scattering off nuclei
Indirect searches: Look for annihilation products.
Positrons: low intrinsic background
Energy correlated to WIMP mass
X 0
X 0
e+
e-
HEATBalloon Experiment
ve
ve
_
AMS-02 experimentConstraints:•9 g at takeoff/landing.•Weight < 14809 lbs•Power = 3 kW•Temperature: -40˚ - +65˚ C•Date rate = 2 Mb/sec•3 year remote operation without servicing
Operational ExperienceAMS-01 engineering test flight10 days: ~ 100 Million events
ISS
The Experiment
TRD: p+ rejection 102-103
ECAL: p+ rejection 103-104
Principle of Transition RadiationHigh energy charged particles crossing boundary between materials of different dielectric constants gives off X-rays.
Detection possible with Lorentz boosts > 300.
Discriminate e+ (TR) / p+ (no TR)
AMS TRD: Proportion tubes and fleece radiator
Construction of AMS TRDTRD Octagon/straw tubesRWTH Aachen
TRD Gas Supply/Circulation SystemMIT – Design CERN & MIT - Construction
TRD Slow Control SystemMIT & INFN Rome
TRD DAQTH Karlsruhe
DAQ Electronics Slow Control and Monitoring
50 liter/hr
DetectorVolume
DistributionSystem
CirculationSystem
Supply/MixingSystem
Vibration TestsThermal Vacuum Tests
Leak Tests
Extensive Testing
328 Modules (5248 straw tubes) Lengths: 0.8 – 2.0 m and 100 μm tolerance
Straw tube walls
Carbon Fiber Structure
Aachen
328 straw modules have been produced:
Gas System: Box S
• Mix Gas:
Xe:CO2 80:20
(to 1% accuracy)
• Refresh Supply Daily:
max 7 liter/day
Engineering model: CERN Flight system: ARDE Corp.
Xe49.5 kg
CO2
4.5 kg
Gas System:Box C• Circulate Gas:
50 liter/hr through Octagon• Monitor gas gain:
Calibration tubes coated with Fe55
Spirometer: Measures CO2 fraction
TRD Gas Slow Control/Monitoring
TRD DAQTRD FE-electronics: 20 Watt for 5248 channels => multiplexed pulse height only
• 20 layer TRD detector in the test beam at CERN in 2000• we have recorded 3 million events providing signals for protons, electrons,
muons and pions at energies from 5-250 GeV
HEAT experiment(experimental data + DM model)
AMS-02 experiment(simulated data + DM model)
Physics Reach
TRD + ECAL
Paolo Maestro: SIENA
AMS on the ISS: 2008
AMS TRD currently under constructionBeam tests: achieve 102-103 p+ rejection to 300 GeVCombined with ECAL will obtain precise e+ spectrum
Summary
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