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

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

6. An inner tracker in Alice…
Challenge: track densities at r = 4 cm (1st pixel layer): up to 100 / cm2
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)
(2º slice)
Federico Antinori - Vertex, Kona - Nov. 2002

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

8. Federico Antinori - Vertex, Kona - Nov. 2002
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. Federico Antinori - Vertex, Kona - Nov. 2002
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): and 97.6 cm
1698 modules
2.6 M channels
Federico Antinori - Vertex, Kona - Nov. 2002

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

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

13. Federico Antinori - Vertex, Kona - Nov. 2002
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): and 59.4 cm
260 modules
133 k channels
Federico Antinori - Vertex, Kona - Nov. 2002

14. Silicon Drift Detector
segmented
2 x 256 anodes
Drift
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)
24/4/ th RRB J. Schukraft

15. Federico Antinori - Vertex, Kona - Nov. 2002
SDD front-end
preamplifiers
analogue
memory
16+16 ADCs
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
PASCAL-64 prototype
CMOS 0.25 mm rad-tol
4x16 kbytes SRAM buffers
40 MHz working frequency
Fast trigger-abort recovery
JTAG interface
Differential inputs
AMBRA-4 prototype
derandomization
&
data transmission
Federico Antinori - Vertex, Kona - Nov. 2002

16. Federico Antinori - Vertex, Kona - Nov. 2002
SDD resolution
Drift distance (mm)
Resolution (mm)
Anode axis (z)
Drift time axis (rj)
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. Federico Antinori - Vertex, Kona - Nov. 2002
Alice SPD
Picture of a solder bump bond (courtesy of VTT)
2 layers, r = 3.9, 7.6 cm
sensitive length (in z): 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
Chip
Sensor
bump-bonded assembly
Chip (150 µm thickness)
Sensor (200 µm thickness)
Federico Antinori - Vertex, Kona - Nov. 2002

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

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

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

24. Federico Antinori - Vertex, Kona - Nov. 2002
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. Federico Antinori - Vertex, Kona - Nov. 2002
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. Benchmark: D0  K-p+ Initial S/B ~ 5 · 10-6 Final S/B ~ 0.1
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)
total
bkgd-subtracted
107 events, all cuts applied
Federico Antinori - Vertex, Kona - Nov. 2002

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

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

31. Federico Antinori - Vertex, Kona - Nov. 2002
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. Federico Antinori - Vertex, Kona - Nov. 2002
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