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The Alice Inner Tracking System

The Alice Inner Tracking System. Federico Antinori (INFN – Padova, Italy). Contents. Introduction Alice and the Inner Tracking System (ITS) ITS subdetectors (a bird’s eye view) Si strips (SSD) Si drifts (SDD) Si pixels (SPD) ITS performance Concluding remarks. Contents. Introduction

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The Alice Inner Tracking System

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  1. The Alice Inner Tracking System Federico Antinori (INFN – Padova, Italy) Federico Antinori - Vertex, Kona - Nov. 2002

  2. Contents • Introduction • Alice and the Inner Tracking System (ITS) • ITS subdetectors (a bird’s eye view) • Si strips (SSD) • Si drifts (SDD) • Si pixels (SPD) • ITS performance • Concluding remarks Federico Antinori - Vertex, Kona - Nov. 2002

  3. Contents • Introduction • Alice and the Inner Tracking System (ITS) • ITS subdetectors (a bird’s eye view) • Si strips (SSD) • Si drifts (SDD) • Si pixels (SPD) • ITS performance • Concluding remarks Federico Antinori - Vertex, Kona - Nov. 2002

  4. Alice • Ultrarelativistic nucleus-nucleus collisions at LHC • Why: • study behaviour of hadronic matter under extreme conditions of heating / compression • investigate confinement / deconfinement, generation of constituent masses Federico Antinori - Vertex, Kona - Nov. 2002

  5. (B< 0.4 T) Federico Antinori - Vertex, Kona - Nov. 2002

  6. Challenge: track densities at r = 4 cm (1st pixel layer): up to 100 / cm2 (2º slice) An inner tracker in Alice… • Vertexing (s, c, b) • strangeness: production sensitive to decrease of effective quark mass in deconfined phase • charm and beauty: “hard” probes of system formed in collision • Improve TPC tracking • high pT (extend TPC lever arm, improve spatial precision) • low pT (standalone ITS) • 1/b2 particle id (analogue r/o for drifts and strips) Federico Antinori - Vertex, Kona - Nov. 2002

  7. 2 strips 2 drifts 2 pixels Rout=43.6 cm Alice ITS • longitudinal coverage: • |h| < 1 (tracking), |h|<2 (multiplicity) Federico Antinori - Vertex, Kona - Nov. 2002

  8. Contents • Introduction • Alice and the Inner Tracking System (ITS) • ITS subdetectors (a bird’s eye view) • Si strips (SSD) • Si drifts (SDD) • Si pixels (SPD) • ITS performance • Concluding remarks Federico Antinori - Vertex, Kona - Nov. 2002

  9. Alice SSD • 2 layers, r = 38.5, 43.6 cm • double sided, stereo angle • (+ 27.5, -7.5) mradian • strips: 95 µm × 40 mm • analogue r/o • module size: 75 × 42 mm2 • sensitive length (in z): 86.2 and 97.6 cm • 1698 modules • 2.6 M channels Federico Antinori - Vertex, Kona - Nov. 2002

  10. SSD front-end: HAL25 • CMOS 0.25 µm radtol layout • 128 analog channels, input pitch 80 µm • Design ENC 200 e- + 8 e-/pF (1.5 µs shape) • Tuneable shaping 1.4  2 µs • Readout at 10 MHz, 200 Ω / 20 pF • Δ current output (±55 µA/MIP, 14 MIP range, linear 5%) • 2.5 V single power supply • JTAG digital, analogue and pulser control Federico Antinori - Vertex, Kona - Nov. 2002

  11. SSD Module Output cables Carbon ladder Cooling tubes Chips Detector Input cables Hybrid SSD module • Al-kapton microcables • all connections are done by TAB-bonding Federico Antinori - Vertex, Kona - Nov. 2002

  12. IReS-Subatech First STAR ladder: december 01 First ladder: pictures Federico Antinori - Vertex, Kona - Nov. 2002

  13. Alice SDD • 2 layers, r = 14.9, 23.8 cm • drift along rj • 294 µm anode pitch • analogue r/o • module size: 75.3 × 70 mm2 • sensitive length (in z): 44.4 and 59.4 cm • 260 modules • 133 k channels Federico Antinori - Vertex, Kona - Nov. 2002

  14. Drift Drift Silicon Drift Detector segmented 2 x 256 anodes MOS charge injectors for drift velocity monitoring Wafer: 5”, NTD, 3 k.cm, 300 m Active area: 7.02  7.53 cm2 guard region implanted HV voltage dividers 256 anodes (294 mm pitch)

  15. PASCAL-64 prototype AMBRA-4 prototype • CMOS 0.25 mm rad-tol • Full custom design: 10*9 mm2 • 64 preamplifiers (t ~ 40ns, RC-CR2 shaping) • 64 analogue memory channels (256 cells) • 32 10-bit linear ADCs • Differential outputs • CMOS 0.25 mm rad-tol • 4x16 kbytes SRAM buffers • 40 MHz working frequency • Fast trigger-abort recovery • JTAG interface • Differential inputs analogue memory preamplifiers 16+16 ADCs derandomization & data transmission SDD front-end Federico Antinori - Vertex, Kona - Nov. 2002

  16. Anode axis (z) • Drift time axis (rj) Resolution (mm) Drift distance (mm) SDD resolution Corrections applied: • doping inhomogeneity map • residual non-linearity of voltage divider • T-dependence of drift velocity • drift-dependent non-linearity of centroid due to diffusion widening Federico Antinori - Vertex, Kona - Nov. 2002

  17. SSD, SDD cooling & support • lightweight, carbon-fibre support ladders • liquid cooling • C6F14 (H20 also considered) Federico Antinori - Vertex, Kona - Nov. 2002

  18. Picture of a solder bump bond (courtesy of VTT) bump-bonded assembly Sensor Chip bump-bonded assembly Sensor (200 µm thickness) Chip (150 µm thickness) Alice SPD • 2 layers, r = 3.9, 7.6 cm • sensitive length (in z): 28.6 cm (for both layers) • hybrid (bump-bonded) silicon pixel assemblies • In / PbSn bumps • pixel size: 50 × 425 µm2 • binary r/o • module size: 12.8 × 69.6 mm2 • 240 modules • 9.8 M channels Federico Antinori - Vertex, Kona - Nov. 2002

  19. 13.5 mm 15.8 mm SPD front-end • Alice1LHCb pixel chip mixed signal (analogue/digital) • commercial 0.25 µm CMOS • radiation tolerant design • 50 µm x 425 µm pixel cell • JTAG controls • 8192 pixel cells • ~100 µW / pixel Federico Antinori - Vertex, Kona - Nov. 2002

  20. Bus Ladder: 5 chips+1 sensor MCM ALICE1LHCb chip Silicon sensor Grounding foil Cooling tube Carbon-fibre sector SPD half-stave Each Stave is built of two HALF-STAVES, read out on the two sides of the barrel, respectively. 193 mm long Federico Antinori - Vertex, Kona - Nov. 2002

  21. 2mm 11mm SMD component 7 7 7 7 6 6 5 5 4 3 2 2 1 1 PIXEL DETECTOR Aluminum Polyimide READOUT CHIP Glue COOLING TUBE SPD bus 7 layer Al-Kapton flex Federico Antinori - Vertex, Kona - Nov. 2002

  22. SPD test beam July 2002, CERN-SPS H4 beam singles online residuals s=16.4µm (along 50 µm axis) ladder Federico Antinori - Vertex, Kona - Nov. 2002

  23. SPD cooling & support • lightweight carbon fibre support sectors • integrated cooling • evaporative C3F8 Federico Antinori - Vertex, Kona - Nov. 2002

  24. Contents • Introduction • Alice and the Inner Tracking System (ITS) • ITS subdetectors (a bird’s eye view) • Si strips (SSD) • Si drifts (SDD) • Si pixels (SPD) • ITS performance • Concluding remarks Federico Antinori - Vertex, Kona - Nov. 2002

  25. Impact Parameter Resolution (rj) • better than 50 µm for pT > 1.3 GeV/c • ~10 µm at high pT Federico Antinori - Vertex, Kona - Nov. 2002

  26. Impact Parameter Resolution (z) Federico Antinori - Vertex, Kona - Nov. 2002

  27. Momentum Resolution • Large effect of ITS on momentum resolution at high pT • high spatial precision • increase of lever arm Federico Antinori - Vertex, Kona - Nov. 2002

  28. 107 events, all cuts applied total bkgd-subtracted Benchmark: D0 K-p+ • Initial S/B ~ 5 · 10-6 • Pb-Pb collisions at LHC with dN/dy = 6000 • invariant mass and particle-id cuts only • Final S/B ~ 0.1 • after vertexing and pointing cuts • Significance S/√(S+B) ≈ 35 • for 107 events (~15 days data taking) Federico Antinori - Vertex, Kona - Nov. 2002

  29. electron tags vs impact parameter Benchmark: B  e± + X • i.p. from ITS • electron id: • TRD (transition radiation) • TPC (dE/dx) Federico Antinori - Vertex, Kona - Nov. 2002

  30. beauty / total e tags vs. impact parameter cut pT> 3 GeV pT> 2 GeV pT> 1 GeV d0threshold (µm) Federico Antinori - Vertex, Kona - Nov. 2002

  31. Contents • Introduction • Alice and the Inner Tracking System (ITS) • ITS subdetectors (a bird’s eye view) • Si strips (SSD) • Si drifts (SDD) • Si pixels (SPD) • ITS performance • Concluding remarks Federico Antinori - Vertex, Kona - Nov. 2002

  32. Concluding remarks • ITS will allow Alice to access heavy flavour sector in nucleus-nucleus collisions • essential information from hot, dense initial stages of collision • ITS design ~ frozen • very tight integration constraints: getting here has taken years of hard work and dedication of tens of physicists and engineers • Very challenging times ahead • tight construction plan in order to be ready for 1st beam (installation in Alice in 2006) Federico Antinori - Vertex, Kona - Nov. 2002

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