1. F.R.Spada – INFN Rome I The TRD of AMS-02 on the International Space Station Francesca Spada University of Rome La Sapienza & INFN Rome I for RWTH Aachen, KNU Daegu, IEKP Karlsruhe, MIT Boston, Università La Sapienza & INFN Roma III Workshop on Advanced TRDs, OSTUNI – September 9, 2005

2. F.R.Spada – INFN Rome I The AMS-02 experiment AMS-02 will fly during 3 years at a mean altitude of 400 km on the ISS (International Space Station) The detector has an acceptance of 0.5 m2 sr and will be used to study the flux of particles coming from space Direct search of Antimatter Indirect search of Dark Matter AMS-02 TRD+ECAL

3. F.R.Spada – INFN Rome I The AMS-02 detector The TRD is placed on top of the detector TRD TOF Trigger -  t = 125 ps CRYOMAGNET and TRACKER B = 0.9 T Charge separation = 1  up to 1 TeV RICH For A ≤ 27, Z ≤ 28, separation > 3  in 1-12 GeV Electromagnetic CALorimeter 3D sampling – lead/scintillating fibres p + rejection > 10 4 in 10-300 GeV Electronics crates

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

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

6. F.R.Spada – INFN Rome I The AMS-02 TRD Radiator: layers of fibre fleece material increase probability of TR emission Interleaved with straw modules filled with high-Z gas mixture 20 layers arranged in a conical octagone structure in alternate projections provide 3D tracking 12 middle layers in x direction 4 top + 4 bottom layers in y direction  vacuum charged particle radiator

7. F.R.Spada – INFN Rome I The fleece radiator Radiator material: LRP 375 BK (Freudenberg) Fleece: 10 µm thick Propylene fibres Density: ρ = 0.06 g/cm 3 Fleece radiator TR-yield

8. F.R.Spada – INFN Rome I The straw tubes 6 mm tubes filled with Xe/CO 2 [80:20] at a pressure of 1250 mbar Tubewall: 72 µm Kapton-Aluminium sandwich Wires: 30 µm W/Au tensioned with 100 g Every module contains 16 straws The structure is stabilized by lengthwise and crosswise stiffeners

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

10. F.R.Spada – INFN Rome I 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 modules installed aluminium + CFC support structure

11. F.R.Spada – INFN Rome I Gas gain Quality check: For each straw module (16 wires) each wire sampled in 10 segments with 55 Fe calculate deviation from average gain get RMS for each module reject modules with RMS>2 To obtain the required proton rejection power, a stringent control over gas parameters is necessary wire dependence due to differnces in wire positioning and tensioning

12. F.R.Spada – INFN Rome I Gas gain 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 o C to -15 o C in 15 days To obtain the required proton rejection power, a stringent control over gas parameters is necessary MLI M-structure TRD dissipative element radiative link radiator Thermal stability through multilayer insulation Temperature monitoring with 200 Dallas temperature sensors in the whole TRD

13. F.R.Spada – INFN Rome I 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 TRD OCTAGON 41 segments 1.4 bar Circulation Box 1.4 bar Manifolds Xe Vessel Mixing Vessel 12 bar CO 2 Vessel Supply Box

14. F.R.Spada – INFN Rome I Gas system – Box S Engineering model: CERN - Flight model: ARDE Corp. Mixture: Xe:CO 2 80:20 to 1% accuracy Gas tanks initial content: Xe: 49.5 kg (8420 ℓ @ 1bar) CO 2 : 4.5 kg (2530 ℓ @ 1bar) Xe 49.5 kg CO 2 4.5 kg

15. F.R.Spada – INFN Rome I Gas System - Box C Gas flow: 1 ℓ/h per gas circuit (41 ℓ/h) Gas gain monitor: Calibration tubes coated with Fe 55 Spirometer to measures CO 2 fraction

16. F.R.Spada – INFN Rome I Gas system control Main DAQ Computer communicates via CAN bus with a control board and then with the dedicated boards for the electomechanical devices Electronic control UGBS UGBC Circulation pump Manifolds UGFV Xe & CO 2 tanksTRD USCM GAS 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

17. F.R.Spada – INFN Rome I Energy deposit in the TRD different highly-relativistic particles leave different energy deposits: E photon ≈  ▪ keV (test beam results on a 60 cm heigth prototype)

18. F.R.Spada – INFN Rome I Proton rejection Energy deposit distribution is normalized, and for each track hit the probability density functions of the hit to belong to a proton or a positron track are calculated Combined probabilities of the event are built: To determine whether a TRD track belongs to a proton or to a positron, a likelihood method is used

19. F.R.Spada – INFN Rome I Proton rejection Likelihood function: L = W e /(W e +W p ) Assuming that events with L 10 2 is reached up to 250 GeV with 90% electron efficiency (MC). 20 GeV Electrons Log Likelihood 160 GeV Protons 0.6 E e- =20 GeV

20. F.R.Spada – INFN Rome I 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 10 6 is needed (ECal provides 10 4 ) The AMS TRD will provide the additional proton rejection factor of 10 2 Straw modules assembly: in progress Gas system mechanical components and electronics: in production Front-end electronics: undergoing space-qualification tests READY FOR FINAL INTEGRATION OF TRD IN 2006

21. F.R.Spada – INFN Rome I Front-end electronics and DAQ Power: 20 Watt for 5248 channels Multiplexed pulsheight only TRD crate