1. The ATLAS Inner Detector Installation and hardware commissioning
11th Pisa Meeting on Advanced Detectors Commissioning and performance of the ATLAS Inner Detector with first beams and cosmic data Attilio Andreazza INFN and Università di Milano for the ATLAS Collaboration
The ATLAS Inner Detector
Installation and hardware commissioning
Data taking in 2008
Subdetectors characterization
Alignment and tracking performance
Outlook

2. A Toroidal LHC Apparatus
A. Andreazza – Commissioning of ATLAS Inner Detector
11th Pisa Meeting on Advanced Detectors, La Biodola, 24 May 2009

3. A. Andreazza – Commissioning of ATLAS Inner Detector
Momentum resolution (pT)/pT = 0.05% pT [GeV/c]  1%
Impact parameter resolution (0.25<||<0.5) (d0) = 10 m 140 m / pT [GeV/c]
2 T solenoidal magnetic field
Acceptance ||<2.5 (transition radiation tracker ||<2)
A. Andreazza – Commissioning of ATLAS Inner Detector
11th Pisa Meeting on Advanced Detectors, La Biodola, 24 May 2009

4. A. Andreazza – Commissioning of ATLAS Inner Detector
Transition Radiation Tracker (TRT)
4 mm diameter straw tubes
351 k channels
resolution 130 m
polypropylene/polyethylene as transition radiation material: electron id 0.5 GeV<E<150 GeV
SemiConductor Tracker (SCT)
4088 modules
80 m strips (40 mrad stereo)
6 M channels
resolution 17 m  580 m
Pixel
1744 modules of pixels
mostly 50 m  400 m
80 M channels
resolution 10 m  110 m
A. Andreazza – Commissioning of ATLAS Inner Detector
11th Pisa Meeting on Advanced Detectors, La Biodola, 24 May 2009

5. Inner Detector Installation
Detector installation timeline:
SCT+TRT barrel: Aug 2006
SCT+TRT end caps: May-Jun 2007
Pixel: 28th Jun 2007
Connectivity completed in Apr 2008
Cooling plant accident 1st May 2008 (Pixel+SCT)
recovered for beam pipe bake-out 23rd Jul – 1st Aug 2008
now operated for >2600 hr
For 2008 data taking
TRT: 98% operational
SCT: 99% barrel 97% end caps
Pixel: 98.5% operational
data taking: 98% barrel, 85% end caps
conservative operation on some cooling circuits, will operate in 2009
Pixel installation
Evaporative C3F8
cooling plant (T=-10C)
A. Andreazza – Commissioning of ATLAS Inner Detector
11th Pisa Meeting on Advanced Detectors, La Biodola, 24 May 2009

6. A. Andreazza – Commissioning of ATLAS Inner Detector
First LHC beams
A. Andreazza – Commissioning of ATLAS Inner Detector
11th Pisa Meeting on Advanced Detectors, La Biodola, 24 May 2009

7. A. Andreazza – Commissioning of ATLAS Inner Detector
First LHC beams
Inner detector partly operational with the first LHC beams:
fear of damage from beam losses in silicon
TRT on
SCT end caps:
20 V bias voltage
1.2 fC threshold (normal operation at 150 V, 1 fC)
SCT barrel and pixels off
Beam splash events:
beam scraping on tertiary collimators (140 m from detector)
multiple halo particles crossing the whole detector at the same time
used for synchronization: SCT 25 ns TRT 1 ns
Beam
SCT end caps 31 19
ToT [ns]
TRT barrel
A. Andreazza – Commissioning of ATLAS Inner Detector
11th Pisa Meeting on Advanced Detectors, La Biodola, 24 May 2009

8. A. Andreazza – Commissioning of ATLAS Inner Detector
Cosmic rays
A. Andreazza – Commissioning of ATLAS Inner Detector
11th Pisa Meeting on Advanced Detectors, La Biodola, 24 May 2009

9. A. Andreazza – Commissioning of ATLAS Inner Detector
2008 Cosmics data-taking
ATLAS combined run September 13th  October 26th
Different magnetic field configurations
Commissioning and calibration month
ID Combined run November 26th December 1st
Magnetic system off
4 statistics in one week
Solenoid off
Solenoid on
TRT tracks
4940k
2670k
SCT tracks
1150k
880k
Pixel tracks
230k
190k
A. Andreazza – Commissioning of ATLAS Inner Detector
11th Pisa Meeting on Advanced Detectors, La Biodola, 24 May 2009

10. A. Andreazza – Commissioning of ATLAS Inner Detector
Level-2 track trigger
For cosmic data, ID acceptance is much narrower than Calorimeter/Muon system: efficient cosmic data taking needs a ID based trigger.
Tracker cannot be read at L1 ...but its information is available for L2 trigger
pointing triggers to be used also during collision
special TRT based trigger for cosmics data taking
Efficiency comparable with offline reconstruction.
commissioning of
L2 track trigger
ID run
A. Andreazza – Commissioning of ATLAS Inner Detector
11th Pisa Meeting on Advanced Detectors, La Biodola, 24 May 2009

11. Calibration and CharacterizaTion

12. Detector calibration (example 1)
Detector characterization and calibration performed before data-taking
Tuning the operation point
Guarantee uniformity of detector response
Particularly relevant for pixels:
80 M channels
charge measurement using Time over Threshold technique
can tune on nominal working point:
4000 e threshold with 40 e dispersion
30 ToT per m.i.p. (20 ke) with 2% dispersion
ATLAS Preliminary
Pixel Time over Threshold
vs. Charge calibrations
Observed ToT spectrum agrees with expectation better than 5%
A. Andreazza – Commissioning of ATLAS Inner Detector
11th Pisa Meeting on Advanced Detectors, La Biodola, 24 May 2009

13. Detector calibration (example 2)
Detector characterization and calibration performed before data-taking
Tuning the operation point
Guarantee uniformity of detector response
SCT foresees to operate not fully depleted:
define working point based on noise vs. bias voltage
threshold 1 fC (6 ke)
ATLAS Preliminary
SCT Barrel
Noise vs. bias voltage
Very low noise occupancy:
TRT <1% noise on track
SCT 10-5
Pixel  (after masking 10-4 noisy channels)
A. Andreazza – Commissioning of ATLAS Inner Detector
11th Pisa Meeting on Advanced Detectors, La Biodola, 24 May 2009

14. A. Andreazza – Commissioning of ATLAS Inner Detector
Detector efficiency
Detector efficiency obtained looking for holes on tracks
When discarding dead modules it is well above 99%  ? 
A. Andreazza – Commissioning of ATLAS Inner Detector
11th Pisa Meeting on Advanced Detectors, La Biodola, 24 May 2009

15. Lorentz angle determination
Drift in silicon is affected by EB effect
Charge is (de)focused along the Lorentz angle direction:
Point displacement: thicknesstan(L)/2
 30 m for pixels
 10 m for SCT
measurement using cluster size vs. incidence angle :
Pixel Barrel
A. Andreazza – Commissioning of ATLAS Inner Detector
11th Pisa Meeting on Advanced Detectors, La Biodola, 24 May 2009

16. Lorentz angle: T dependence
The data quality, both in terms of conditions monitoring and reconstruction allows already to see small effects:
Expected from parameterization
da/dT = mrad/K
Small effect: ~0.1 m/K
...but nice it can be observed
Parameterization: C. Jacoboni et al., Solid-State Electronics 20 (1977)
T. Lari, ATL-INDET
A. Andreazza – Commissioning of ATLAS Inner Detector
11th Pisa Meeting on Advanced Detectors, La Biodola, 24 May 2009

17. TRT threshold behavior
ATLAS preliminary
TRT provide “bubble chamber” quality tracking and transition radiation for high momentum particles.
Double threshold:
low threshold for tracking
high threshold to discriminate possible transition radiation.
Observed transition radiation from high p muons!
ATLAS preliminary
A. Andreazza – Commissioning of ATLAS Inner Detector
11th Pisa Meeting on Advanced Detectors, La Biodola, 24 May 2009

18. ALIGNMENT AND TRACKING PERFORMANCE

19. Inner detector alignment
Alignment based on minimization of residuals: r = measurements– extrapolation
Different strategies tested:
global 2
used for Silicon and TRT
take full correlation into account
invert 6N6N matrix
local 2
Si-only ignore correlation term between objects
invert N 66 matrices
robust
Si-only
residuals for special tracks (example overlapping modules)
N=number of objects in alignment
A. Andreazza – Commissioning of ATLAS Inner Detector
11th Pisa Meeting on Advanced Detectors, La Biodola, 24 May 2009

20. A. Andreazza – Commissioning of ATLAS Inner Detector
Limited statistic/not uniform coverage:
N cannot be all Si objects from start.
progress aligning macro structures layers, half shells, staves... modules
use constraints from mechanical structures
SCT alignment supplemented by optical FSI (Frequency Scanning Interferometry) system.
A. Andreazza – Commissioning of ATLAS Inner Detector
11th Pisa Meeting on Advanced Detectors, La Biodola, 24 May 2009

21. Residuals distribution
perfect alignment =16 m
after alignment =174 m
after alignment =24 m
p>2 GeV
perfect alignment =24 m
RMS of residuals from first alignment already in the ballpark expected from perfect alignment.
N.B.: these are not intrinsic resolutions
extrapolation error is not negligible,
multiple scattering contribution.
after alignment =30 m
p>2 GeV
A. Andreazza – Commissioning of ATLAS Inner Detector
11th Pisa Meeting on Advanced Detectors, La Biodola, 24 May 2009

22. Track parameter resolution
Resolution of track parameters can be obtained:
splitting the track in two segments
compare extrapolation at the interaction point of the segments.
Resolution not far from perfect alignment,
already before LHC startup!
perfect alignment =32 m
p>2 GeV
after alignment =49 m
N.B.:
plots before correcting for 2
integrated over full momentum spectrum
perfect alignment =4 TeV-1
after alignment =5 TeV-1
p>2 GeV
A. Andreazza – Commissioning of ATLAS Inner Detector
11th Pisa Meeting on Advanced Detectors, La Biodola, 24 May 2009

23. A. Andreazza – Commissioning of ATLAS Inner Detector
Summary and outlook
The ATLAS inner detector has been commissioned with cosmic rays and single beam data in 2008:
Detector successfully operated from September to December
Extensive characterization and calibrations performed at the pit
After alignment tracking performance already adequate for initial data taking.
Preparing for 2009 data taking:
Some repair ongoing on the Si detectors:
Evaporative cooling system have been significantly reworked to improve modularity and reliability.
Optical transmitters in the ROD, which showed ESD damages due to the fabrication process, are being replaced with components manufactured with a tighter QA plan.
Expect to run in 2009 with 99% of SCT and 98.5% Pixel operational
To do list:
check alignment stability with initial cosmics
improve statistics for horizontal tracks
A. Andreazza – Commissioning of ATLAS Inner Detector
11th Pisa Meeting on Advanced Detectors, La Biodola, 24 May 2009

24. Summary and outlook Watching for LHC collisions!
but further significant improvements in detector understanding require collision data:
end caps characterization and alignment
performance on pointing tracks
vertex reconstruction
Watching for LHC collisions!
For more details, see posters:
J. Weingarten, Results from the Commissioning of the ATLAS Pixel Detector with Cosmics Data
H. Pernegger, ATLAS Silicon Microstrip Tracker Commissioning and Silicon Sensor Performance
R. Moles, Alignment of the ATLAS Inner Detector Tracking System
A. Andreazza – Commissioning of ATLAS Inner Detector
11th Pisa Meeting on Advanced Detectors, La Biodola, 24 May 2009

25. BACKUP

26. A. Andreazza – Commissioning of ATLAS Inner Detector
Optical link
Optical communication system between on and off detector electronics.
Need to be tuned to work in safe error free region.
Observed high rate of failure of VCSELS in TX plugins used by the Si detectors:
consistent with electrostatic damage:
well know failure mode for VCSEL
shift if IV curve typical of ESD
could be reproduced with ESD gun
components being replaced by new lot manufactured with stricter ESD protection.
error free region
phase [ns]
PiN threshold [DAC]
10
01
clock edge
A. Andreazza – Commissioning of ATLAS Inner Detector
11th Pisa Meeting on Advanced Detectors, La Biodola, 24 May 2009

27. Cosmics ray properties
Cosmic and Test Beam
specialized tracking algorithm developed for detector commissioning
NewTracking
default tracking algorithm for collision data
performance in agreement with dedicated algorithm
A. Andreazza – Commissioning of ATLAS Inner Detector
11th Pisa Meeting on Advanced Detectors, La Biodola, 24 May 2009

28. Cosmics ray properties
N.B.: blue and red are two different tracking algorithms
A. Andreazza – Commissioning of ATLAS Inner Detector
11th Pisa Meeting on Advanced Detectors, La Biodola, 24 May 2009

29. Front-end electronics concept
Fast charge amplifier with constant current feedback.
Fast discriminator with tunable threshold (7-bit DAC)
Storage of hits during the trigger latency time in 64 “End of Column” memory buffers for each column pair of 2×160 pixels
A. Andreazza – Commissioning of ATLAS Inner Detector
11th Pisa Meeting on Advanced Detectors, La Biodola, 24 May 2009

30. SCT Front-end electronics
A. Andreazza – Commissioning of ATLAS Inner Detector
11th Pisa Meeting on Advanced Detectors, La Biodola, 24 May 2009

31. Pixel Detector calibration uniformity
Pixel detector channels can be individually tuned to provide a high uniformity of response.
Threshold dispersion
At the end of tuning, pixels differentiate only for noise levels:
Different pixel sizes
A. Andreazza – Commissioning of ATLAS Inner Detector
11th Pisa Meeting on Advanced Detectors, La Biodola, 24 May 2009

32. Processing and calibration data flow
Detector offline calibrations
Quasi-online alignment
A. Andreazza – Commissioning of ATLAS Inner Detector
11th Pisa Meeting on Advanced Detectors, La Biodola, 24 May 2009

33. A. Andreazza – Commissioning of ATLAS Inner Detector
24h calibration loop
After data taking some devoted stream are user for calibrations:
general purpose express stream
in cosmics replaced by “extended” ESDs
specialized streams (alignment)
During data taking, expected to provide calibrations within 24 h
in some cases mainly monitoring
Not fully in place for 2008 running:
single run statistics not enough for some calibrations
but most algorithms exercised
Pixel noise mask determination
provides random noise occupancy O(10-10)
Pixel charge interpolation
A. Andreazza – Commissioning of ATLAS Inner Detector
11th Pisa Meeting on Advanced Detectors, La Biodola, 24 May 2009

34. Muon energy loss in calorimeters
Comparing standalone muon and ID tracks, it is possible to measure energy loss in the calorimeter:
Measurement consistent with expectations: PID-Muon 3 GeV/c
A. Andreazza – Commissioning of ATLAS Inner Detector
11th Pisa Meeting on Advanced Detectors, La Biodola, 24 May 2009

35. Material distribution
A. Andreazza – Commissioning of ATLAS Inner Detector
11th Pisa Meeting on Advanced Detectors, La Biodola, 24 May 2009