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BTeV Silicon Pixel Detector

BTeV Silicon Pixel Detector. Test beam results 1999-2000 Talk given by G. Chiodini – Fermilab Research Technique Seminar - Fermilab – July 21, 2000. Overview. BTeV experiment Intersection region at the Tevatron Silicon pixel vertex detector Silicon pixel detector Test beam setup

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BTeV Silicon Pixel Detector

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  1. BTeV Silicon Pixel Detector Test beam results 1999-2000 Talk given by G. Chiodini – Fermilab Research Technique Seminar - Fermilab – July 21, 2000

  2. Overview • BTeV experiment • Intersection region at the Tevatron • Silicon pixel vertex detector • Silicon pixel detector • Test beam setup • SSD telescope and DAQ • Pixel planes tested • Test beam results • Pixel calibration • Charge collection • Charge-sharing • Spatial resolution • Magnetic field measurements • 4 Plane pixel telescope • Further studies • 0.25mm radiation tolerant FPIX2 • Pixel module bench test • Mechanics and cooling • Conclusions G. Chiodini - Fermilab

  3. BTeV is an experiment to study Heavy Quark • Physicsin the C0 IR of the Tevatron: • Mixing • CP violation • Rare Decays • … BTeV experiment • 1.6T Dipole magnet centered on the IR • Forward geometry (1.9<h<4.5) • Symmetric two arm spectrometer • Detached tracks in the 1stLevel trigger G. Chiodini - Fermilab

  4. BTeV experimentIntersection region at the Tevatron Luminosity=2×1032cm-2s-1 BR<1.5×10-5 L • 4×1011 b-hadrons/107sec • B0, B+, Bs (Lb, Bc) • Forward region <g>»6 • <2 interactions> per BCO • High density of tracks • Hadronic decays Ang. Correl. bb production Resolution B decay length in BTeV G. Chiodini - Fermilab

  5. BTeV experimentBTeV silicon pixel vertex detector • Decay time resolution (CP studies) Þ • good spatial resolution • high statistics data samples • 1st L trigger: prim. vertex and detached tracks Þ • high resolution points • detector close to the interaction region • low combinations and noise hits • Pixel vertex detector Þ • space points (x,y,z) • radiation hard (2×1014 particles cm-2y-1) • low occupancy and noise Planar pixel vertex detector Hybrid pixel detector Readout chip Sensor bump G. Chiodini - Fermilab

  6. BTeV experimentBTeV silicon pixel vertex detector – global layout 0.595m 1.482m Pixel frame lateral view cooling pipes Pixel frame end view G. Chiodini - Fermilab

  7. BTeV experimentBTeV silicon pixel vertex detector – half plane and module VCSEL optical driver Pin diode optical receiver Data serializer Control, monitoring, and, timing track beam • Module • ~ 1Gbyte/s • Rad-Hard components • (maybe optical device out rad. Area) • Half plane • 20% overlap of sensors in a single plane • 0.89% radiation length per plane G. Chiodini - Fermilab

  8. BTeV experimentSilicon pixel detector - hybrid detector • Independent development and optimizations of readout chip and sensor • Require 5000 bump-bonding per cm2 to connect the pixel cells to the readout cells • Bump-bonding of flipped chip • 2 acceptable bump metal (10-5 <bump failure<10-4): Indium (In) and solder (SnPb) • Under Bump Metal (Cr, TiW, Cu, Au, …): adhesion layer, diffusion barrier and oxide prevention • Bonding process:Indium Þ Metal bump both side, room T, pressure • Solder Þ Metal bump one side, high T, reflow G. Chiodini - Fermilab

  9. BTeV experimentSilicon pixel detector – sensor Vdep=depletion voltage , d=detector thickness, e=Si dielectric constant, Neff=effective impurity concentration Harsh radiation environment Þ p-type doping Þ high Vdep Þ detector must operate partially depleted after irradiation n+/n/p technology type inversion Inter-pixel isolation p-side multi-guard ring Surface current path Si-vacuum 0V G. Chiodini - Fermilab

  10. BTeV experimentSilicon pixel detector – sensor Sensor radiation hardness can be improved by defects engineering According to the ROSE (RD48) Collaboration a factor of 2 in the depletion voltage can be gain using oxygen enriched silicon G. Chiodini - Fermilab

  11. BTeV experimentSilicon pixel detector – FPIXn readout chip • Three generations of readout chip each one with a specific goal: • FPIX0 Þto establish a viable front-end • Hewlett Packard (HP) 0.8mm CMOS process • 12cols x 64 rows • analog voltage output • simple column based digital logic • FPIX1 Þto establish high speed digital logic • HP 0.5mm CMOS process • 18cols x 160 rows • 2-bit flash ADC in each cells • Complete column based digital architecture • FPIX2 ÞRadiation tolerant design • 0.25mm CMOS process (DSM) with Rad-Hard rules (guard rings and enclosed geometry transistors) • Redesigned analog FE feedback and leakage compensation • Simpler and faster digital section than FPIX1 • preFPIX2T (2cols x 160rows of FPIX2) • FPIX2 submission in few months G. Chiodini - Fermilab

  12. BTeV experimentSilicon pixel detector – FPIX readout chip FPIX1 detailed block diagram • 132 ns bunch crossing (BCO) • Column-based and data driven architecture G. Chiodini - Fermilab

  13. BTeV Silicon Pixel Detector Test beam results 1999-2000 J.A. Appel, J.N. Butler, G. Cardoso, H. Cheung, G. Chiodini, D.C. Christian, E.E. Gottschalk, B.K. Hall, J. Hoff, P. A. Kasper, R. Kutschke, S.W.Kwan, A. Mekkaoui, R. Yarema, and S. Zimmermann Fermi National Accelerator Laboratory C. Newsom - University of Iowa A. Colautti, D. Menasce, and S. Sala - INFN(Milan) R. Coluccia and M. Di Corato - Universita’ di Milano M.Artuso and J.C. Wang – Syracuse University Particular thanks to W. Baker, C. Brown, J. Kilmer, T.Kobilarcik, beams division, operators, MAB, SiDET … G. Chiodini - Fermilab

  14. Setup: SSD telescope and DAQ Magnet DAQ E T H E R N E T • I/O Board • - Controls and Initializes • 4 pixel readout chips • - GPIB controller: HV, • thresholds and pulser • Automatic pixel calibration VME COMPUTER I/O BOARD STAR TFIB G. Chiodini - Fermilab

  15. Samples of FPIX0 and FPIX1 readout chips bump-bonded to ATLAS sensor prototypes Setup: Pixel planes tested n+np indium bump-bonding 50x400 mm2 cells FPIX0 64x12cells 8 bit external ADC FPIX1 160x18cells 2 bit internal FADC • ST1-CiS p-stop • ST2-CiS p-spray • Bonded active area 3.2x4.4mm2 • Two ST1-Seiko p-stop • ST2-Seiko p-spray • Bonded active area 8x6.8mm2 G. Chiodini - Fermilab

  16. FPIX0 Inner Board Setup: Pixel planes tested Analog Buffer 8 bit ADC Pixel detector Light protected FPIX1 Inner Board PC Board Interface G. Chiodini - Fermilab

  17. Setup: Pixel planes tested Close-up middle station Slots at different angles : 0, 5 10, 15, 20, 30 degrees G. Chiodini - Fermilab

  18. Results:pixel calibration - pulse generator FPIX0 bump-bonded to ST1 CiS p-stop Qth=2500±400e- Qnoise=106±13e- Qnoise,ADC=400±96e- Dynamic range £1.5MIP G. Chiodini - Fermilab

  19. Results: Pixel calibration - X ray sources Vth0 = Threshold knob G. Chiodini - Fermilab

  20. Results: Charge collectionSingle chip CiS p-spray <Q>=21500e- Qmp=18300e- Charge losses 400 mm 50 mm Charge losses are thought not to be intrinsic to the p-spray technology but a feature of this particular sensor design. G. Chiodini - Fermilab

  21. Results: Charge collectionSingle chip CiS p-stop <Q>=30100e- Qmp=24700e- Saturation bump for CS=1 • The Landau distribution convoluted with a Gaussian function fit well the charge distribution. • Only less than 0.7 % of the events have a signal less than 15000 e-. G. Chiodini - Fermilab

  22. Results: Charge collectionSingle chip CiS p-stop Landau distribution Single pixel sQmp Qmp »4.2% G. Chiodini - Fermilab

  23. Track inclination Results: charge-sharing Diffusion Relative fraction of cluster sizes (CS) FPIX0 CiS p-stop Qth=2500e- Vbias=-140V Vdep=-85V c) Delta rays emission G. Chiodini - Fermilab

  24. Results: charge-sharingDelta rays emission G. Chiodini - Fermilab

  25. Results: spatial resolutionPosition Finding Algorithm Charge Sharing Q Charge fluctuations qR qL x Track position is correlated to the charge of the left and right hit in the cluster Digital algorithm Head-tail algorithm where It reduces to charge-weighting for N=2 and f=pitch/2h G. Chiodini - Fermilab

  26. Results: spatial resolutionh distribution and correlations G. Chiodini - Fermilab

  27. Results: spatial resolutionEta function f(h) G. Chiodini - Fermilab

  28. Results: spatial resolutionGaussian fit residual distribution ST1 CiS FPIX0 detector Analog Pulse height used x y 50mm 400mm CS=1,…,6 • Xpred = projection of the kalman fit on the plane using all the planes, BUT the one under test (spred = 2.1 mm) . • Xmeas= coordinate measured by the plane under test using the head-tail analog interpolation. G. Chiodini - Fermilab

  29. Results: spatial resolutionSpatial resolution vs angle ST1 CiS FPIX0 detector Qth= 2500e- Vbias= 140V Vdep= 85V Excellent spatial resolution at all angles using analog information G. Chiodini - Fermilab

  30. Results: spatial resolutionComparison between detectors Qth=2500e- Qth=2200e- Qth=3780e- • Most of the difference in spatial resolution between FPIX0 (nominal 8 bit) and FPIX1(2 bit) is due to the different readout threshold. • The charge losses in FPIX0 p-spray degrades the spatial resolution • BTeV requirement: better than 9 mm G. Chiodini - Fermilab

  31. Results: spatial resolutionComparison with simulation Good agreement between data and BTeV pixel detector simulation package with input parameters describing the detector properties (such as Vbias, Vdep, …) corresponding to the sensors used in the test beam Comparison FPIX0 beam test data and simulation for binary and 8 bit analog readout Comparison FPIX1 beam test data and simulation for 2 bit analog readout and 2 values of threshold G. Chiodini - Fermilab

  32. Results: spatial resolutionComparison 8-bit ADC and 2-bit ADC FPIX0(8-bit) Qth=3720e- FPIX1(2-bit) Qth=3780e- Going from nominal 8-bit to 2-bit analog information the resolution degrade by less than 1mm FPIX0(8-bit) Qth=2500e- Comparison nominal 8-bit FPIX0 and “2-bit” FPIX0 degraded by software G. Chiodini - Fermilab

  33. Results: spatial resolutionBias voltage For track angle > 5 degrees no degradation of the resolution when the detector is over depleted. ST1 CiS FPIX0 detector Nominal bias voltage G. Chiodini - Fermilab

  34. Results: spatial resolutionThreshold As expected, larger readout threshold degrades the spatial resolution. ST1 CiS FPIX0 detector Nominal threshold G. Chiodini - Fermilab

  35. Results: spatial resolution2D spatial resolution ST1 CiS FPIX0 detector Sigma= 4.65±0.10 mm x y 400+400 mm Good spatial resolution also when the charge isshared between the long pixel dimension. G. Chiodini - Fermilab

  36. Results: spatial resolutionNon-Gaussian resolution function CS=1 and track angle < 10 degs: Square convoluted with a Gaussian CS>1 track angle < 10 degs and all CS track angle > 10 degs: Gaussian + power law • Non-Gaussian part: • 15% of events: half in the constant • term and half in the tails • power law with an exponent ³2 G. Chiodini - Fermilab

  37. Results: Magnetic field measurementFPIX0 p-stop in the fringe field Charge collection in magnetic field Fringe field up to 0.6T Ratio double/single Vbias=-190V ageometry » aLorentz=mH,eB G. Chiodini - Fermilab

  38. Results: 4 plane pixel telescope 2.2mm thick diamond target 1mm Excellent tracking capability even in high track enviroment Interaction vertex in the target Thousands of triggered multiple interactions events 1mm Interaction vertex in pixel plane G. Chiodini - Fermilab

  39. Radiation dose in BTeV near the beam comparable to ATLAS first layer (1014cm-2y-1) • Pre-FPIX2 prototypes implemented in commercial 0.25mm CMOS process from two vendors • Pre-FPIX2 irradiation tests with Co60 at Argonne confirm the RD49 Collaboration results at CERN Further studies: Radiation Hard FE ALICE/LHCb-RICH chip in DSM irradiated up to 30 Mrad (g,p): no large Single Event Upset rate and no evidence of Gate Rupture Failure preFPIX2T g irradiated at 33Mrad equivalent to 10 years running for BTeV at full luminosity of 2×1032cm-2s-1 G. Chiodini - Fermilab

  40. L AYER PAIR Cu / Ni / Au L aye r P a ir 1 D i e l ec tri c L aye r pa ir 2 Condu c to r Further studies: Module bench test ATLAS 16 chips T1 p-stop 5 Fpix1 chips HDI flex circuit M1 M2 M3 M4 Upilex-SGA • Multilayer Kapton High Density Interconnect cable. • Very high density routing design: • Line center spacing = 40 mm • Via center spacing = 208mm (350mm) G. Chiodini - Fermilab

  41. Further studies: Mechanics and cooling Nonporous carbon tubes, “flocking” carbon, and “fuzzy” carbon Shingled detector Heat exchanger test heated up by two aluminum plates G. Chiodini - Fermilab

  42. Conclusions • The FPIX-type FE performs well as expected and needed • GREAT data sample to gain operational experience with pixel silicon detectors (3M useful events) • Primary features of the beam test results are clear: • Very good resolution at all angles • 3 bit ADC good choice for FPIX2 • Little sensitivity to the bias voltage • Excellent tracking capability • Good agreement between simulation and real data indicates a good understanding of the detector performance • Rapid progress in global systems issue:bump-bonding, rad-hard sensor, rad hard front-end, modules, cooling, mechanical support, … G. Chiodini - Fermilab

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