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