Overview and Status of the ATLAS Pixel Detector

Overview and Status of the ATLAS Pixel Detector

Overview and Status of the ATLAS Pixel Detector Claudia Gemme, CERN/INFN-Genova on behalf of the ATLAS Pixel Community 10th ICATPP Conference, Como, Oct 8th 2007 ATLAS: A Toroidal LHC ApparatuS The ATLAS Pixel Detector B-Layer Layer-1 B-Layer Disks

Beampip e The Pixel Detector is the innermost part of the tracking system for the ATLAS experiment. It consists of three barrel layers and six disks, covering with three precise measurement points the region up to =2.5. Innermost layer (B-layer) at R=5 cm. A total of 80 million channels and a sensitive area of 1.6 m2. Modules will operate in an environment temperature below 0C and inside a 2T solenoidal magnetic field. Components have been tested

to be rad-hard up to: NIEL > 1015 1 MeV n/cm2 dose > 500 kGy Module concept Modules are the building block of the Pixel Detector. There will be 1456 barrel modules and 288 forward modules. Each module has 46080 pixels in an area of ~10 cm2 Module are placed on cooling/support structure (staves in the barrel, sectors for the endcaps).

Modules components: Sensors are n+ pixels on n substrate, 60.8mm16.4 mm 250 m active silicon volume. Pixel size 50 m (R) 400 m (). Bump bonds between Si sensor and 16 front-end electronics chips (both SnPb and In bumps used). Module Controller Chip on flex hybrid to perform distribution of commands and event building Micro-cable (~1m) connected to service panel (PP0) Front-End Electronics I Each FE connected to 2880 pixels

FE receive commands, clock, Level-1 trigger from controller chip at 40 Mbit/s rate Charge injection circuitry allows to measure/calibrate relevant parameters. Pixel-level control logic (14bits) to adjust e.g. Threshold and Time-over-Threshold (ToT). Each channel can be individually tuned, to get uniform response: threshold: 4000 e threshold dispersion: 40-90 e noise: 140-180 e- Front-End Electronics II Ideal pulse shape is almost triangular with fast rise and slow return to baseline. Timing of this signal is critical 1. Timewalk:

low pulse height signals arrive later than high pulse height; if delay is too high, the pulse is associated to the subsequent bunch crossing. uniform efficiency requires good synchronization. 2. Time over Threshold (ToT) used to interpolate position of multi-hit clusters as a function of =Q2/(Q1+Q2) Time over Threshold for a m.i.p. tuned to 30 clock cycles 20 ns In-time threshold 1 m.i.p. timewalk ToT Service Panels and Optoboard Service panels bring services

out of inner detector volume (~7m) Active part: optoboards that provide electrical/optical data conversion 272 Optoboards: Data-out: 8-VCSEL array (40 to 160 Mbit/s) to offdetector electronics (RODs) Data-in: PiN diode receives commands, clock, Lv1 Commissioning of End-Cap (Fall 06) In fall 2006 before final detector integration: performed a 10% system test One end-cap (144 modules) Scintillators for cosmics

trigger One prototype service panel Services close to final version operation at -10 C, using evaporative cooling; connection to off-detector readout electronics via optical fibres Achievements: Commission services Commission DAQ and offline with cosmic and random triggers. Service quarter panel Pixel endcap A 8

More on Optoboards Three problems affects the optoboards VCSELs: Temperature dependence Low optical power at low T, but optoboards coupled to cooling Forced the use of heaters to keep the optoboards at room temperature. Common-Series-Resistance Symptom: VCSEL dying during production (aging process?) No dead VCSEL observed since Oct. 2006 10C 5C -5C -10C

-15C -25C -20C Channel Slow-Turn-On: Shown later not to affect operation after tuning of optical threshold 9 Cosmics run I ns Delay VS module number Disk 0 Hits in time with trigger Flat noise distributio n

ns 10 ns ns Disk 1 Disk 2 Timewalk spreads hits through different bunch crossings The LVL1 distribution is sensitive to module timing and has been used to Check module relative synchronization with resolution better than 1 ns. Cosmics run II Occupancy: hit probability per bunch crossing of a pixel. True random

occupancy is order of 10-10 Efficiency can be computed using particles which cross overlapping modules in the same disk (24% of tracks) Average efficiency ~99% After masking 89 (out of 1.6106) pixels with occupancy greater than 10-4 Signal Noise 10-10

* Pixel Package Integration (MarJun07) Service panel Connection of cooling pipes Beampipe End-cap 12 Permanent connection of micro-cables SQP integration and Connectivity Test Connectivity test to check Permanent module connection to services Last chance to repair before

installation in the pit! The first time the full detector is readout using the full readout chain 1 module Connectivity test setup: Use cosmic test hardware (can only test ~10% of pixel at a time) No cooling available: possible switching on only a reduced part of the detector at a time. Hardware T interlock 2 modules on 3 modules on

Results of the Connectivity Test Check optical and As built detector quality: electrical connections: LV, HV, Env sensors Micro-cables mapping Optical fiber mapping Optoboard tunability Results: Only 2 module failures: One broken HV cable LV short problem 1 PiN and 1 VCSEL single channel dead Every optoboard tunable

Required DCS/DAQ development Localised inefficiencies ~0.12% 2 unusable modules 3 dead FE chips None of these in the B-layer! Individual bad pixels ~0.2% Layer 2: Layer 1: B-Layer: Disks: 0.29% 0.20% 0.07% 0.15% Most relevant failures: disconnected bumps noisy channels

reduced charge collection ... and then diving June 25 June 29 Pixel Commissioning plans Atlas combined run M5 (22 Oct 5 Nov): Data taking with off-detector electronics, few modules and Simulated ROD events. Connection of the detector (Dec/Jan): Test/commissioning of electrical/optical/cooling connections Sign-off of the detector (Feb/March): Commissioning of the cooling system with detector powered Calibration and noise measurements

Data taking Combined run with ID sub-systems for ID sign-off Cosmics run with Atlas (Mar/April) Conclusions The ATLAS Pixel detector construction has been completed and the detector has been installed on June 29! Detailed information of each of the 80M channels: Unfortunately final connection to the services will not be possible until December: operation only in March. the fraction of defective pixels is below 0.4% One endcap has been used

for system commissioning: matching of optical components proved to be critical reconstruction and simulation software validated using cosmics rays: noise occupancy O(10-10) efficiency >99% resolution matches MC expectation. ...to be awakened by waiting As Sleeping Beauty afor cosmics kiss Prince Charming

Backup Common Serial Resistance (CSR) Symptom: like a dead VCSEL Some failed boards recovered A procedure is developed to measure the resistance of the inaccessible CSR and the worst boards are rejected.(~7% ) The reason is not understood yet Conductive epoxy thickness? Time dependent ? Optical Power Ratios (H/R Suspicious STO Optical Power Ratio (High/Random) Connections at PP1 A Quadrant at PP1

Type 1 cables Type 2 cables (connectors only) Optofibers faceplate Corrugated panels (Outer/Inner)

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