The ALICE Transition Radiation Detector Design and Performance

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The ALICE Transition Radiation Detector Design
and Performance
Johannes P. Wessels, Universität Münster for the
ALICE TRD Collaboration

• detector principle and overview
• results from testbeam measurements
• dE/dx
• transition radiation
• electron/pion separation
• position and angular resolution
• performance of electronics
• status of the project

IEEE Nuclear Science Symposium, Rome, Oct. 16-22,
2004
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Transition Radiation Detector (TRD)

• Purpose
• electron ID in central barrel pgt1 GeV/c
• fast trigger for high pt particles
• Parameters
• 540 modules -gt 760m2
• length 7m
• anticipated X/X0 15
• 28 m3 Xe/CO2 (8515)
• 1.2 million channels
• 17 million pixels
• 15 TB/s on-detector bandwidth
• weight 21 t
• total power 60kW

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Principle of Operation
7 mm
31 mm
48 mm

• two purposes PID momentum measurement

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Radiator

• polypropylene fibers (17 ?m)
• CF-backed ROHACELL foam
• irregular sandwich radiator
• parameterized for simulations

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Full Size Radiator
size 1200x1600 mm2 deformation at
center 1 mm _at_ 1 mbar
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Mounting of Electronics
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Radiator Comparison

• method likelihood on total charge averaged over
  4 detectors
• extrapolated to six layers
• pion rejection of 100 achieved over large
  momentum range
• little dependence on actual radiator producer

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?-Rejection vs. incident angle

• slight deterioration of pion rejection at small
  angles (0o-2o)
• not frequent in ALICE
• space charge effects diminish signal
• not included in simulations
• low gas gain preferable

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Resolution vs. Incident Angle

• quantitative understanding of all resolution
  effects
• significant improvement in position resolution
  with tail merging and tail cancellation
• position resolution better than 300 ?m
• angular resolution better than 0.8o

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Resolution vs. Signal-to-Noise

• resolution better for pions at given S/N ratio
• average signal larger for electrons
• comparable resolution for electrons and pions
• angular resolution smaller for electrons with
  radiator -gt L-shell fluorescence

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TRD electronics chain
PASA
TRAP - digital chip
40mm
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Preamp Shaper (PASA)

• 18 4th order preamplifier/shapers with
  differential outputs (21) 12 mV/fC, 13 mW/channel
• digital test structure for chip verification
• size of chip 3030 µm x 7280 µm
• full production received thinned to 300 µm

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PASA test results
crosstalk as function of inter-pad capacitance
gain 12.2mV/fC dynamic range 0.15fC..165fC shapi
ng time 40ns FWHM 120ns differential output
-1..1V noise at 25pF 702e noise slope
21e/pF integral non-linearity lt0.16 power
consumption 13 mW/channel
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TRD Stack Preparation

• test of 6 chambers at CERN this week
• e/? - beam up to 10 GeV/c

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Summary

• pion rejection and tracking capability fulfill
  specs
• quantitative understanding of
• dE/dx, position and angular resolution
• TR production absorption
• promising results of PASA and digital ASIC
  evaluation
• good trigger capability for high pt charged
  particles
• starting series production now
• aim to be ready for first events in 2007
• physics performance report
• http//alice.web.cern.ch/ALICE/ppr

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ALICE TRD Collaboration

• C. Adler, A. Andronic, V. Angelov, H.
  Appelshäuser, C. Baumann, T. Blank, C. Blume, P.
  Braun-Munzinger, D. Bucher, O. Busch,
  V. Catanescu, V. Chepurnov, S. Chernenko, M.
  Ciobanu, H. Daues, D. Emschermann, O.
  Fateev, S. Freuen, P. Foka, C. Garabatos, H.
  Gemmeke, R. Glasow, H. Gottschlag, T. Gunji, M.
  Gutfleisch, H. Hamagaki, N. Heine, N. Herrmann,
  M. Inuzuka, E. Kislov, V. Lindenstruth, C.
  Lippmann, W. Ludolphs, T. Mahmoud, A. Marin, J.
  Mercado, D. Miskowiec, Y. Panebratsev, V.
  Petracek, M. Petrovici, C. Reichling, K.
  Reygers, A. Sandoval, R. Santo, R. Schicker, R.
  Schneider, S. Sedykh, R.S. Simon, L. Smykov, J.
  Stachel, H. Stelzer, H. Tilsner, G. Tsiledakis,
  I. Rusanov, W. Verhoeven, B. Vulpescu, J.W., B.
  Windelband, C. Xu, V. Yurevich, Y. Zanevsky, O.
  Zaudtke
• Physikalisches Institut, Universität
  Heidelberg, Germany
• GSI, Darmstadt, Germany
• Kirchhoff Institut, Universität Heidelberg,
  Germany
• FZ Karlsruhe, Germany
• Universität Frankfurt, Germany
• Universität Münster, Germany
• NIPNE, Bucharest, Romania
• JINR, Dubna, Russia
• University of Tokyo, Japan

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