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TRD Technology at ALICE

TRD Technology at ALICE. Matthias Hartig Johann-Wolfgang Goethe Universität Frankfurt/Main. Overview. ALICE Experiment ALICE TRD Chamber Design Front End Electronic Performance TRD Overview HERMES TRD NOMAD TRD AMS TRD Summary / Outlook. Large Hadron Collider.

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TRD Technology at ALICE

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  1. TRD Technology at ALICE Matthias Hartig Johann-Wolfgang Goethe Universität Frankfurt/Main

  2. Overview • ALICE Experiment • ALICE TRD • Chamber Design • Front End Electronic • Performance • TRD Overview • HERMES TRD • NOMAD TRD • AMS TRD • Summary / Outlook

  3. Large Hadron Collider Mont Blanc Genf CERN

  4. HMPID PID (RICH) @ high pt TOF PID TRD Electron ID TPC Tracking, PID ITS Vertexing Low pt tracking MUON m-pairs PMD g multiplicity PHOS g,p0 ALICE Experiment FMD, V0, T0, ZDC (not shown) Trigger, multiplicity, centrality EMCAL(not shown) Jet-calorimetry

  5. The ALICE Experiment

  6. ALICE ExperimentRequirements • Robust tracking performance • Needs to digest highest multiplicities (O(105) tracks !) • Need to cover low pt region (~100 MeV/c ) • Soft physics important for event characterization • But the high pt region as well (>100 GeV/c ) • Hard probes transmit information about early phase • Good PID capabilities over large pt-range essential • Many effects are flavour dependent • Sensitivity to rare probes • Heavy flavour, quarkonia, photons, ...

  7. ALICE ExperimentPID Capabilities (relativistic rise) TPC: (dE/dx) = 5.5(pp) – 6.5(Pb-Pb) % TOF:  < 100 ps TRD:  suppression  10-2 @ 90% e-efficiency

  8. Produced by fast charged particles crossing the boundary between materials with different dielectrical constants production probability ~a = 1/137 per boundary Characteristic: energy spectrum in keV region angel of emission ~1/g Spectrum determined by: number and distance of the surfaces thickness and plasmafrequence of the material Velocity of the charged particle (g > 1000) Radiator: Regular foils Fibre material Foam Transition Radiation DetectorTransition Radiation Measured spectrum of 2 GeV/c electrons

  9. Transition Radiation DetectorSchematic View • Radiator: • irregular structure • - Polypropylen fibers • - Rohacel foam (frame) • 4.8 cm thick • self supporting • Gas: • Xe/CO2 85/15 % • Drift region: • 3 cm length • 700 V/cm • 75 mm CuBe wires • Amplification region: • W-Au-platedwires 25 mm • gain ~ 10000 • Readout: • cathode pads • 8 mm (bending plane) • 70 mm in z/beam-direction • 10 MHz

  10. Transition Radiation DetectorDesign • Large area chambers (1-1,7 m²) • -> need high rigidity • Low rad. length (15%Xo) • -> low Z, low mass material

  11. TOF supermodule TRD Supermodule Transition Radiation DetectorSetup TRD Supermodul • TRD in Numbers: • 540 Chambers • 6 Layers • 18 Sectors (Supermodule) • Total Area: 736 m2 • Gasvolume: 27,2 m3 • Auflösung (r) 400 mm • Number of Readout Channels: 1,2 Millionen TPC

  12. Electron Identification PerformanceResult of Test Beam Data Typical signal of single particle LQ Method: Likelihood with total charge LQX Method: total charge + position of max. cluster PID with neural network • e/-discrimination< 10-2 • For 90% e-efficiency

  13. Readout Board (ROB) • 8 (6) ROBs per chamber • 7 different ROBs • 16+1 MCM per Board • Readout of 18 channels per MCM 2 x Optical Readout Interfaces Detector Control System Front End ElectronicOverview

  14. Front End ElectronicReadout Board / Multi-chip Module • Analog part (PASA): • Preamplifier/shaper • Convrsion gain 12.4 mV/fC • Shaping time 120 ns (FWHM) • Equivalent noise ~700 e • Digital Part (TRAP): • ADC • Preprocessor, digital filters • Hit selection • Tracklet processing at 120 MHz 160cm 120cm • 260 000 CPUs working in parallel during readout • Measured Noise on the chamber ~1200 e

  15. Front End ElectronicDetector Control System • 1 DCS board per chamber: • FPGA and ARM core running Linux OS • Control of voltage regulators • MCM configuration • Clock and trigger distribution • Also used for other detectors 160cm

  16. Front End ElectronicOptical Readout Interface • 2 ORI boards per chamber: • Connects 4 (3) ROBs to GTU • High speed readout: 2.5 GBit optical link 160cm 120cm

  17. TRD TriggerOnline Tracking • Challenges: • tracking of all charge particles • time budget of 6.1 ms • Trigger Requirements: • electron and electron pairs • with high pt (> 2GeV/c) • Local Tracking Unit (LTU) • on each chamber • linear tracklets fit • ship tracklets to GTU • Global Tracking Unit (GTU) • find high momentum tracks through all 6 layers • generate trigger

  18. Offline TRD TrackingStandalone Track Resolution • Cluster reconstruction: • charge sharing between pads • pad response function • tail cancellation • TR absorption • Track position • Track angel • In bending plane: • Hit resolution < 400 mm (for each time bin) • Angular resolution < 1 deg. (for each plane) • Track angular resolution: < 0.4 deg.

  19. Offline Tracking PerformanceEfficiency and Resolution for Pb+Pb • Efficiency: • high software track-finding efficiency • lower combined track efficiency • (geometrical acceptance, particle decay ) • Efficiency independent of track multiplicity dNch/dy = 6000 • Momentum resolution: • long lever arm ITS + TPC +TRD (4cm <r<370cm) • resolution better for low multiplicity (p+p) • pt/pt  5 % at 100 GeV/c and B = 0.5 T

  20. HERMES TRDLepton Scattering Experiment • DIS measurement at 27 GeV at HERA • electron identification: • TRD, preshower, calorimeter • (RICH,TOF)

  21. HERMES TRDLepton Scattering Experiment • Aktive area 0.75 x 3.25 m2 • 2 x 6 modules • Irregular radiator • polypropylen fibers • 6.35 cm thick • Readout • MWPC • flexible windows • Gaps to keep MWPC thickness • 90/10 % Xe/CH4 • Result: • dismantled 2007 • PRF > 102 for > 2 GeV/c • more than 10 years successful operation

  22. NOMAD TRDNeutrino Oscillation Experiment • Appearance of nm -> nt • nt + N-> t- + X • t- -> e- + ne +nt • Background from ne in neutrino beam • Total pion rejection > 105 at 90% electron efficienty at 1-50 GeV/c • TRD 103,preshower, EM calorimeter • End of operation 1999 • Aktive Area 2.85 x 2.85 m2 • 9 modules • Regular radiator • 315 polypropylen foils • 15 mm thick • 250 mm space • Readout • 176 straw tubes • 3 m long • 16 mm diameter • 80/20 % Xe/CH4

  23. AMS TRDAntimatter Search in the Universe • Space based Detector • AMS 1: space shuttle • AMS 2: 3 y on the ISS • 6 modules • Irregular radiator • polypropylen fibers • 2.00 cm thick • 80/20 % Xe/CH4

  24. Summary ALICE TRD chambers 80 % ready FEE Integration / SM production 30 % ready MCM configuration needs fine tuning 4 SM installed At least 3 successful TRDs TRD powerful tool to identify electrons from 1 – 100 GeV/c Summary / Outlook Outlook • Gas detector for TR measurement ? • Slow • Xe is expensive • Xe difficult to get • New development of radiator material ?

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