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The Transition Radiation Detector of AMS-02 for the indirect search of Dark Matter

The Transition Radiation Detector of AMS-02 for the indirect search of Dark Matter. Francesca Spada University of Rome La Sapienza & INFN for RWTH Aachen, KNU Daegu, IEKP Karlsruhe, MIT Boston, Università La Sapienza & INFN Roma

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The Transition Radiation Detector of AMS-02 for the indirect search of Dark Matter

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  1. The Transition Radiation Detector of AMS-02 for the indirect search of Dark Matter Francesca Spada University of Rome La Sapienza & INFN for RWTH Aachen, KNU Daegu, IEKP Karlsruhe, MIT Boston, Università La Sapienza & INFN Roma 6th International Workshop on the Identification of Dark Matter Rhodes, 11-16 september 2006 F.R.Spada – INFN Rome I

  2. AMS-02 – Alpha Magnetic Spectrometer AMS-02 will fly at least 3 years on the ISS (International Space Station) AMS Acceptance: 0.45 m² sr Weight: 6700 kg Dimensions: 3.5x2.3x2.3 m3 Power: 2500 W Mission duration: ≥3 years ISS Dimensions: 108 x 80 m2 Orbit: Elliptic (400 km) Inclination 51.57°, 15.62 revs/d DT: -150 ÷ +30 °C SPACE SHUTTLE Acceleration: 3 (6) g Launch: 2009 F.R.Spada – INFN Rome I

  3. The AMS-02 detector The TRD is placed on top of the detector TRD Electronics crates TOF Trigger - st = 125 ps RICH For A ≤ 27, Z ≤ 28, separation > 3s in 1-12 GeV Electromagnetic CALorimeter 3D sampling – lead/scintillating fibres p+ rejection > 104 in 10-300 GeV CRYOMAGNET and TRACKER B = 0.9 T Charge separation = 1s up to 1 TeV F.R.Spada – INFN Rome I

  4. p+ e+ mc= 130 GeV AMS-02 – Physics motivations • Spectroscopy of cosmic particles with AMS-02 allows • direct search of Antimatter (antihelium nuclei) • indirect search of Dark Matter • Observation of positrons of 10 – 100 GeV in the cosmic rays spectrum is a signature of the annihilation of dark matter candidates like neutralinos χ Positron excess observed in the region around 50 GeV by HEAT Further investigation is worthwile! Cosmic rays spectrum is dominated by protons: n(p)/n(e+) = O(104) To detect positrons with a 90% efficiency: proton rejection factor of 106 is needed joint use of ECAL and TRD (Transition Radiation Detector) F.R.Spada – INFN Rome I

  5. AMS-02 TRD Ovewrview • The AMS-02 TRD essentials • The radiator and the straw tubes • The gas system • Gas gain • Thermal control • Signal extraction F.R.Spada – INFN Rome I

  6. Construction Octagon/straw tubes RWTH Aachen Gas Supply/Circulation System MIT – Design CERN & MIT - Construction Slow Control System INFN Rome I TRD DAQ TH Karlsruhe F.R.Spada – INFN Rome I

  7. charged particle radiator g g g g g g vacuum The Transition Radiation • A highly relativistic charged particle crossing the interface between two media with different dielectric constants emits a transition radiation in the X-ray region • This can be used for particle discrimiation at very high energies • Emission probability at each crossing ~ 1% • To increase the TR emission the number of interfaces crossed must be maximized F.R.Spada – INFN Rome I

  8. Radiator: layers of fibre fleece material increase probability of TR emission The AMS-02 TRD • Interleaved with straw modules filled with high-Z gas mixture • 20 layers arranged in a conical octagone structure in alternate projections provide 3D tracking F.R.Spada – INFN Rome I

  9. Computer Tomography X-ray of the straw tubes F.R.Spada – INFN Rome I

  10. Tubewall: 72 µm Kapton-Aluminium sandwich Polycarbonate endpieces AW 134 glue for potting Copper-Tellurium crimp connectors to the electronic board Double O-ring gas connectors Gas tightness • Forseen gas storage: 8420 ℓ for Xe at 1 bar (49.5 Kg) 2530 ℓ for CO2 at 1 bar (4.5 Kg) • Measured CO2 leak rate (diffusion through the straw walls): 0.23·10-6ℓ·mbar/s/m • Total TRD CO2 leak rate (tubes + polycarbonate endpieces): 1.5·10−2ℓ·mbar/s • TRD operation pressure: 1.4 bar a 287 ℓ loss of CO2 over 3 years safety factor ~ 8 Gas tightness of the straw modules over 3 years is a key point for the operation of the TRD in space F.R.Spada – INFN Rome I

  11. Support structure • conical octagon structure of aluminum honeycomb with carbon fibre walls 201 cm x 62 cm, accuracy < 100 μm Total weight: 207 kg matches stability and lightness requirements aluminium + CFC support structure modules installed F.R.Spada – INFN Rome I

  12. Gas gain To obtain the required proton rejection power, a stringent control over gas parameters is necessary • gas density dependence • Example: a 3°C temperature change causes a 1% gas density variation, which implies a gas gain variation of about 5% • Temperature variation during the orbit: from T = +35 oC to -15 oC in 15 days Thermal stability through multilayer insulation and heaters T>0°C Temperature monitoring with 200 Dallas temperature sensors in the whole TRD F.R.Spada – INFN Rome I

  13. Circulation Box 1.4 bar Manifolds Supply Box Xe Vessel 107 bar TRD OCTAGON 41 segments 1.4 bar Mixing Vessel 12 bar CO2 Vessel 65 bar Gas system • During the operation the gas mixture is circulated in the TRD through a manifold system from a circulation system and refilled by a supply box containing the gas tanks F.R.Spada – INFN Rome I

  14. Gas system – Box S Engineering model: CERN - Flight model: ARDE Corp. • Mixture: Xe:CO2 80:20 to 1% accuracy Gas tanks initial content: Xe: 49.5 kg (8420 ℓ @ 1bar) CO2: 4.5 kg (2530 ℓ @ 1bar) Xe 49.5 kg CO2 4.5 kg F.R.Spada – INFN Rome I

  15. Gas System - Box C Gas flow: 1 ℓ/h per gas circuit (41 ℓ/h) Gas gain monitor: • Calibration tubes coated with Fe55 • Spirometer to measures CO2 fraction F.R.Spada – INFN Rome I

  16. Xe & CO2 tanks Circulation pump TRD Manifolds GAS Electronic control UGBS UGBC UGFV USCM Gas system control • Main DAQ Computer communicates via CAN bus with a control board and then with the dedicated boards for the electomechanical devices Also monitor of pressure and temperature in the gas system and in the TRD modules, and of the composition of the gas mixture In case of overpressure, or power or communication failure, actions are taken that drive the system into a safe status F.R.Spada – INFN Rome I

  17. p/e+ Separation in AMS-02 The TR emission in a TRD protorype has been studied at a test beam comparing 20 GeV electrons and 160 GeV protons Overall proton rejection factorfor a 90% electron efficiency: 106 ECAL Shower-Shape: 103ECAL+Tracker E / p: 10 TRD TR-Cluster: 102÷ 103 F.R.Spada – INFN Rome I

  18. 20 GeV Electrons 160 GeV Protons Log Likelihood Log Likelihood 0.6 0.6 Proton rejection in the TRD • Likelihood function:L = We /(We+Wp) • Assuming that events with L < 0.6 are from light particles, a proton rejection factor >102 is reached up to 250 GeV with 90% electron efficiency (MC). Ee-=20 GeV F.R.Spada – INFN Rome I

  19. Conclusions • AMS will perform direct search of antimatter and indirect search of dark matter measuring charged particles and nuclei up to TeV energies • To detect positrons with a 90% efficiency, an overall proton rejection factor of 106 is needed (ECal provides 104) • The AMS TRD will provide the additional proton rejection factor of at least 102 • Straw modules assembly: finished • Gas system mechanical components and electronics: in qualification • Front-end electronics: finished READY FOR FINAL INTEGRATION OF TRD IN 2007 AMS LAUNCH FORSEEN IN 2009 F.R.Spada – INFN Rome I

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