1. Performance and operation experience of the Atlas Semiconductor Tracker and Pixel Detector at the LHC Ewa Stanecka PAS, Cracow for the ATLAS collaboration Vertex 2013

2. Outline  Introduction  Operations and performance  Radiation damage  Combined tracking performance  Technical stop activities  Conclusions 15/09/2013Ewa Stanecka: Vertex20132

3. LHC and ATLAS detector  The Large Hadron Collider at CERN is the world’s highest energy particle accelerator.  Beams of 4TeV protons can be made to collide head-on at 4 points around the ring, where particle detectors record the results of the collisions. 15/09/2013Ewa Stanecka: Vertex20133  ATLAS is designed to:  Investigate the TeV scale  Search for the Higgs boson  Search beyond the Standard Model, Supersymmetry, Mini-black holes, Leptoquarks,Extradimensions  Make precision measurements of SM

4. ATLAS Inner Detector The ID consists of: – Pixel detector – Semiconductor Tracker (SCT) –Transition Radiation Tracker(TRT) All within 2T solenoid B-field. Pixel and SCT kept cold by evaporative cooling, using C 3 F 8 15/09/2013Ewa Stanecka: Vertex20134 Precision tracking at LHC luminosity over 5 units in η Precise primary/secondary vertex reconstruction Excellent b-tagging in jets Electron, muon, tau, b- and c-hadron reconstruction covers : |η| < 2.5 (2.0 for TRT)

5. Pixel Detector  3 barrel layers, 2 x 3- layer end-cap disks  1744 pixel modules, 80M+ channels  Intrinsic Resolution 10 μm/115 μm (R ϕ /z)  Cooled to average T = -13ºC 15/09/2013Ewa Stanecka: Vertex20135

6. Pixel Detector Module Sensor:  250 μm thick n-on-n sensor  47232 (328 x 144) pixels  Typical pixel size 50 x 400 μm 2 (50 x 600 μm 2 pixels in gaps between FE chips)  Bias voltage 150 – 600 V Readout:  16 FE chips, 2880 pixels each  Zero suppression in the FE chip, MCC builds module event  Pulse height measured by means of Time over Threshold  Data transfer 40 – 160 MHz depending on layer 15/09/2013 Ewa Stanecka: Vertex2013 6

7. Semiconductor Tracker (SCT)  4 barrel layers, 9 disks per end-cap  4088 modules, 6.3M channels (61 m 2 )  Intrinsic Resolution = 17 μm / 580 μm (R ϕ /z)  Operational T = -8ºC to ~5ºC  C 3 F 8 Evaporative Cooling, in common with Pixel detector 15/09/2013Ewa Stanecka: Vertex20137

8. SCT modules  Back-to-back sensors glued to highly thermally conductive substrates for mechanical thermal stability, wire-bonded to form ~12cm long strips  40mrad stereo angle between strips on opposite sides  1536 channels (768 on each side)  5.6W/module (rising to ~10W after 10 yrs LHC)  up to 500V sensor bias (nominal 150V)  Readout by 12 rad-hard ASICs (binary hit-no-hit) 15/09/2013Ewa Stanecka: Vertex20138 2112 barrel modules one shape 1976 end-cap modules 3 shapes

9. LHC/ATLAS data taking LHC delivered: -48,1 pb -1 in 2010 -5,61 fb -1 in 2011 -23,3 fb -1 in 2012 -31,2 nb -1 in 2013 50ns bunch spacing. 15/09/2013Ewa Stanecka: Vertex20139  ATLAS Trigger system selects interesting events.  “Level 1” hardware trigger, rate ~70kHz  Detector subsystems must read out their data at this rate!  Software-based High Level Trigger further reduces rate to 400Hz for data recording.

10. LHC/ATLAS data taking  High instantaneous luminosity leads to up to 40 pp interactions per bunch crossing (μ).  High detector occupancy.  Non-zero rate of Single Event Upsets (SEUs) 15/09/2013Ewa Stanecka: Vertex201310

11. SCT data taking 99% of readout channels operational 15/09/2013Ewa Stanecka: Vertex201311  SCT bias voltage maintained at safe 50V level until “Stable Beams” declared, at which point HV is ramped to 150V.  Automated action in 2012, though with shifter oversight. Year 201020112012 Lumi-weighted SCT good data fraction 99.9%99.6%99.1% TotalOut-of-readout (Barrel/Endcap) Fraction (Total) Modules408811/190.73% Chips4905638/170.11% Strips62791684111/72520.18%  Automatic recovery (reconfiguration) of modules giving persistent readout errors.  Reconfiguration of all modules every 30 minutes during running (recover from SEUs).

12. Evolution of SCT configuration 15/09/2013Ewa Stanecka: Vertex201312

13. SCT Efficiency  Define intrinsic hit efficiency as “hits-per- possible-hit”, i.e. ignore non-operational modules from both numerator and denominator.  To measure efficiency of each module side, perform track fits ignoring that side, and then see if we see a hit. 15/09/2013Ewa Stanecka: Vertex201313 Efficiency well above 99% for all layers+sides!

14. SCT single Hit Efficiency 15/09/2013Ewa Stanecka: Vertex201314  The mean intrinsic hit efficiency for each layer of the SCT measured in 8 TeV proton-proton collisions.  Taken from a special run in 2012 with a low number of p-p interactions per crossing.

15. SCT Noise  Too many fake hits from noise could impair the pattern recognition in tracking software.  SCT was designed to have noise occupancy lower than 5x10 -4.  Occupancy can be measured either in standalone calibration runs, or as part of normal ATLAS data-taking (look in empty bunch-crossings).  Noise is well within design limits. 15/09/2013Ewa Stanecka: Vertex201315

16. Evolution of SCT Noise and Gain 15/09/2013Ewa Stanecka: Vertex201316

17. Pixel data taking 15/09/2013Ewa Stanecka: Vertex201317 Year 201020112012 Lumi-weighted Pixel good data fraction 99.1%99.8%99.9%  99.9% Pixel data taking efficiency in 2012  95% of the modules are active in data taking in 2012  Inoperable fraction gets addressed in the LS1 repairs

18. Readout limitations 15/09/2013Ewa Stanecka: Vertex201318 In case of high burst data rate or SEUs module busies, timeouts and desynchronization are frequent Mitigated by real-time recovery actions, resulting in great reduction of dead time: O(s) → O(ms) Module desynchronization addressed by automatic reconfiguration of the affected module. Limitations will be removed by the installation of new ROD/BOC system for Layer 2 which provide higher through-put.

19. Pixel threshold and noise Threshold and noise is determined by measuring the discriminator activation curve as a function of the injected charge The Pixel Detector is operated at a threshold of 3500 e-, typical dispersion 40 e-. Typical noise is since the beginning below 200 e- for regular sized pixels. Online Noise Mask of Pixels with noise occupancy > 10 -6 hits/event Noise occupancy O(10 -9 ) hits/pixel/beam crossing (after masking) 15/09/2013Ewa Stanecka: Vertex201319

20. Pixel Time-over-threshold (ToT )  Time-over-threshold (ToT, length of discriminator signal) information (in units of 25 ns) is read out together with the hit information → measurement of the deposited charge  Time-over-threshold tuned pixel by pixel to 30 BC @ 20ke  The ToT resolution achieved with the internal calibration is sufficient to distinguish p from K in minimum bias events below 1 GeV/c. The dE/dx resolution is 12% 15/09/2013Ewa Stanecka: Vertex201320

21. Pixel Hit-to-Track Association Efficiency In all active modules including dead and masked pixels Efficiency ~99% for nearly all parts Slightly lower efficiency in the outermost discs due to individual modules 15/09/2013Ewa Stanecka: Vertex201321

22. Radiation damage 15/09/2013Ewa Stanecka: Vertex201322 Expected Radiation Dose and Depletion Voltage Shift – Status as of End 2012

23. SCT Radiation damage Evolution of Leakage current in SCT Barrels compared to a prediction 15/09/2013Ewa Stanecka: Vertex201323 Radiation damage is not yet having a significant impact on the operating characteristics of SCT modules.

24. Pixel Radiation Damage  Radiation damage in sensor visible in leakage current and shift of depletion voltage  Type inversion happened early 2012 for B-Layer, late 2012 for Layer 1 and not yet for Layer 2  Depletion voltage/depth can be determined by  using crosstalk method before type inversion  track depth method after type inversion 15/09/2013Ewa Stanecka: Vertex201324 Cooling stops

25. Tracking performance Up to 4,000 tracks per event in high-pile-up conditions seen in 2012! 15/09/2013Ewa Stanecka: Vertex201325 Excellent agreement between data and Monte Carlo simulation.

26. Impact parameter and vertex reconstruction 15/09/2013Ewa Stanecka: Vertex201326 Precise track resolution of the ATLAS Inner Detector result in an transverse impact parameter of O(10)μm Very good vertex and secondary vertices position resolution

27. Inner Detector Radiology 15/09/2013Ewa Stanecka: Vertex201327 Secondary hadron vertex distribution is used for accurate material map

28. Technical stop activities - SCT SCT power and cooling were switched off in February 2013 –Cooling and powering of SCT is expected to return in Mid 2014 Numerous SCT consolidation activities – Upgrade/expansion of SCT-DAQ Installation of an additional 38 Read-Out Drivers (RODs) These will remove a critical DAQ bottleneck and will allow us to be able to read out the SCT up to 3x10 34 cm -2 s -1 (assuming 25ns bunch spacing) Installation of new TX optical engines in the Back Of Crate (BOC) cards –ROD firmware upgrade 15/09/2013Ewa Stanecka: Vertex201328

29. Technical stop activities - Pixel  Pixel Detector was extracted from the ATLAS detector in the beginning of LS1and since April 2013 is in a lab on the surface for refurbishment  New Pixel Quarter Service Panels nSQP will be integrated into the Pixel detector, after the old services have been dismounted  New position of opto-boards allows maintenance each year  allow Layer 1 readout speed upgrade to 160 Mbit/s  Layer 2 DAQ Upgrade:  operate single link at 80 Mbit/s  additional off-detector hardware will be installed (ROD/BOC)  Install fourth pixel layer: Insertable B-Layer (IBL) at R= 3.3 (see talk by Fabian Huegging on Thursday) 15/09/2013Ewa Stanecka: Vertex201329

30. Technical stop activities – ID common infrastructure  Testing/repair of evaporative heaters system, which ensures thermal shield between silicon detectors and TRT operating in room temperature  Commissioning of new Thermosiphon cooling system which will replace compressor based cooling system  Cleanness: avoiding the pollution produced by working components like compressors and/or pumps.  Leak reduction: due to the reduction of the connections as a direct consequence of the simplification of the main loop.  Accessibility: allows a full time access for preventive and corrective maintenance to all the active parts of the system.  Reliability: increases the reliability using standard industrial material for the Chiller and passive components for the main loop 15/09/2013Ewa Stanecka: Vertex201330

31. Conclusions  The Pixel detector and SCT have performed extremely well during LHC Run 1 and have contributed to the rich and diverse program of ATLAS physics.  Efficiency and noise match or exceed design specifications.  We have put great emphasis on configuration stability reliability and up time during operations.  The effects of radiation damage (increase in leakage currents) are entirely consistent with our expectations (Hamburg/Dortmund model).  Excellent combined tracking performance.  Ongoing upgrades and consolidation of SCT and Pixel detector during the first long shut-down of the LHC to improve the cooling system and expand the DAQ system to be able to cope with 3 times the design luminosity. 15/09/2013Ewa Stanecka: Vertex201331