The ALICE Transition Radiation Detector Design and Performance  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 Johannes P. Wessels, Universität Münster for the ALICE TRD Collaboration IEEE Nuclear Science Symposium, Rome, Oct , 2004

ALICE Setup ALICE setup ITS TPC TRD TOF PHOS HMPID MUON ARM PMD FMD

Transition Radiation Detector (TRD)  Purpose: electron ID in central barrel p>1 GeV/c fast trigger for high p t particles  Parameters: 540 modules -> ~760m 2 length: 7m anticipated X/X 0 ~ 15 % 28 m 3 Xe/CO 2 (85:15) 1.2 million channels 17 million pixels 15 TB/s on-detector bandwidth weight ~ 21 t total power: ~ 60kW

Principle of Operation  two purposes: PID & momentum measurement 7 mm 31 mm 48 mm

Radiator  polypropylene fibers (~17  m)  CF-backed ROHACELL foam  irregular sandwich radiator  parameterized for simulations

Full Size Radiator size: 1200x1600 mm 2 deformation at center 1 1 mbar

Assembly of TRD Chambers - precision mounting jigs - 3D measurement system

Mounting of Electronics

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

Improvement of  -rejection  bi-dimensional likelihood analysis improves pion rejection  probability of finding largest cluster in a given time bin

 -Rejection Using Neural Network  feed-forward neural network w. 15 input neurons  2 hidden layers  factor 3-7 improvement over LQX method  pion rejection of

 -Rejection vs. incident angle  slight deterioration of pion rejection at small angles (0 o -2 o )  not frequent in ALICE  space charge effects diminish signal  not included in simulations  low gas gain preferable

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 0.8 o

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 -> L-shell fluorescence

TRD electronics chain PASA TRAP - digital chip 40mm

Preamp Shaper (PASA)  18 4 th 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

PASA – test results gain: 12.2mV/fC dynamic range: 0.15fC..165fC shaping time: 40ns FWHM: 120ns differential output: V noise at 25pF: 702e noise slope: 21e/pF integral non-linearity: <0.16% power consumption: 13 mW/channel crosstalk as function of inter-pad capacitance

ADC Performance Muthers, Tielert, Kaiserslautern 0.18  m CMOS 10 bit, 10 Ms/s 0.1 mm 2, 9.5 mW ENOB: 1 MHz DNL: -0.4;0.6 INL: -0.8;0.7

Filter Non- linearity Pedestal Gain Tail Crosstalk

TRD Trigger Timing Drift time t [ns] relevantpipelineADCoutput Calculate  fit PASAADC Tracklet Preprocessor TPP TRD event buffer CalculateTracklets Tracklet Preprocessor TPP Tracklet Processor TP event buffer Tracklet Merger TM Data ship Global Tracking GTU TRD N. Herrmann, V. Lindenstruth, B. Vulpescu

TRD Stack Preparation  test of 6 chambers at CERN this week  e/  - beam up to 10 GeV/c

Cosmic Ray Track  readout with MCMs  Ar/CO 2 (85/15)  V anode = 1400 V  v d = 2.6 cm/  s

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 p t charged particles  starting series production now  aim to be ready for first events in 2007  physics performance report

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

Transition Radiation  Poisson distribution for measured TR photons  some loss of TR clusters in analysis 2 GeV/c  Parameterization as regular foil stack  270 interfaces, 10  m thick, 80  m spacing  no momentum dependence in simulation