The ATLAS Pixel Detector

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The ATLAS Pixel Detector

• Pixel 2002 Workshop
• M. Garcia-Sciveres
• Lawrence Berkeley National Lab

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Aerial View of the LHC Site
Circumference of 27 km
Main CERN Site
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A Toroidal LHC ApparatuS
LHC beam pipe
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ATLAS Inner Detector
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Pixel Detector
3 hit design
1.3m
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ATLAS Pixel Collaboration

• University of Toronto, Canada
• Academy of Sciences of the Czech Republic
• Czech Technical University
• Charles University, Czech Republic
• CPPM, France
• U. of Bonn, Germany
• U. of Dortmund, Germany
• MPI, Germany
• U. of Siegen, Germany
• U. of Wuppertal, Germany
• INFN Genova, Italy

• INFN Milano, Italy
• INFN Udine, Italy
• Academia Sinica, Taiwan
• SUNY Albany, USA
• LBNL, USA
• Iowa State U., USA
• U. of New Mexico, USA
• Ohio State U., USA
• U. of Oklahoma, USA
• UC Santa Cruz, USA
• U. of Wisconsin Madison. USA

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Detector Parameters

• 3 Barrel layers, 33 Disks covering hlt2.5
• Inner radius 5cm Outer radius 12cm
• n on n oxygenated sensors, 400mm (z,R) x 50mm
  (phi) pixels.
• Number of channels 67M (barrel) 13M (disks).
• Readout type zero-suppressed time over
  threshold.
• Lifetime Dose, 1015 neq/cm2, 50MRad.
• LHC Interaction rate 40MHz.
• Max readout rate 160Gb/sec gt 7KHz trigger at 1
  occupancy.
• ASICs 0.25mm CMOS with rad. Tolerant layout .
• AC signal protocol LVDS in active volume,
  optical outside.
• Active volume operating power 6.5kW at 2V
• Silicon operating temperature lt0oC
• Cooling system evaporative C3F8.
• Radiation length at normal incidence 10 R.L.

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Performance
Test beam measurement of single Front End chip
bump bonded assembly. For single hits expect
ssqrt(12) x pitch 14mm.
s9mm
s13mm
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Test beam measurement of hit efficiency
unirradiated and fully irradiated assemblies.
Efficiency
0
Time (10ns/div.)
Time (10ns/div.)
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Sensors

• 2 Manufacturers CIS and Tesla
• Basic Requirements
• Leakage current after 1015 neq/cm2 lt50nA / pixel
• Total input capacitance lt400fF
• Inter-pixel capacitance small
• Signal after irradiation gt10Ke-

Simulation of 70 depletion voltage at innermost
layer. 150 LHC nominal fluence.
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Sensors (cont.)
100mm wafer with 3 tiles, n side
Detail of p-side multi guard ring structure
Charge collection efficiency (meas)
n implants and bias grid
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Custom ASIC Electronics

• Suite of chips all fabricated in 0.25mm
  commercial bulk CMOS.
• Use circuit library with special layout rules for
  radiation tolerance (based on RD49 library)

Module Control Chip Manages data control
between modules 16 chips
Optical interface chips
Front End Chip 2880 channels
Doric (from PIN diode to decoded LVDS)
VDC array (from LVDS to laser diodes)
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Readout architecture
Optical driver
FE chip
Module Control Chip
100m
sensor
FE chip
1m
Optical receiver
FE chip
power
HV bias
bump bonds
optical
LVDS control
LVDS data out
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The Bare Module
Solder Bumps
Indium Bumps
OR
50mm
16 chips. 46,080 bump bonds
Xray of bumps
2cm
Sensor
ICs
6.3cm
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Pixel Module
Pigtail (beyond)
Sensor
ASICs
Flex Hybrid (green)
Bumps
Wirebonds
Schematic Cross Section
(through here)
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Interconnection
Flex hybrid. Interconnects 16 Front End chips to
1 Module Control. Distributes power to all chips
and bias to sensor. All connections wirebonded.
Flex pigtail Al/Cu wire bundle connect flex
hybrid to patch panels at either end of pixel
detector.
Transition to optical at ends of pixel detector.
Power continues on Al/Cu wires to end or inner
detector.
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Production line oriented design
Bar code
Fully assembled module on frame

• Flex hybrids mounted on frames immediately after
  fabrication.
• All module assembly proceeds on frame.
• Allows safe shipping handling, testing,
  bar-code tracking, storage.
• Modules are removed from frame (by cutting
  sacrificial ends of flex) only at the time of
  attaching to a local support.

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Detector building blocks
Sector is replicated to form disks. 33 modules
(back side looks the same)
Bi-stave assembly Is replicated to form Barrel
layers. 2x13 modules
Same unit repeated many times for production line
assembly, uniformity of work at different sites
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Mechanics and services

• In the detector volume
• high power density
• minimum material (gt no thermal mass)
• cold operation
• lt10mm alignment maintained between room and
  operating temperatures
• Remain cold dry even during down times
• Outside detector volume
• Supply 2V power from 100m away with acceptable
  voltage drop
• Supply adequate cooling with minimal plumbing
• Meet overall detector geometry and installation
  constraints
• Minimize material in front of calorimeters at low
  angles

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Module support
Stave
Exploded view of sector
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Global Support
Solid computer model of frame (cutaway view)
disks
Need very stiff low mass structures with near
zero CTE (build at room temperature- operate down
to 25C). Use carbon composites, intense computer
modeling simulation
disks
barrel
F.E.A.
TV Holograph image
Real life prototype Disk section of frame
1st mode 515.6 Hz
1st mode546 Hz
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Pixel and Beam Pipe Assembly
A package that can be inserted in place into
the inner detector (and removed also)
Fits into a support tube that provides
mechanical support, but also electrical and
environmental isolation from the outside. Cold
inside dry inside out no matter outside
conditions
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Construction Timeline

• Sensor production started
• Pre-production chip submission Dec. 2002
• Production chip submission Summer 2003
• End Production Module assembly Dec. 2004
• Start integration at CERN Jan. 2005
• Start lowering detector into cavern Fall 2005
• Begin commissioning Spring 2006
• First collisions 2007