# Presentation: 806070

## Status of the ATLAS Pixel Detector APS April Meeting 2004

- Sven Vahsen,
- Lawrence Berkeley Laboratory,
- for the ATLAS Pixel Collaboration

## Overview: The scale of things

- 1.3 m

- ATLAS

- ATLAS Pixel Detector
- Module.
- Production just started.
- Will focus on modules
- today.

- 6 cm

- Pixel

- x1744

- 50 x 400 μm

- x46080

- ATLAS Pixel Detector
-  Innermost sub detector, provides
-  precise tracking in high    multiplicity environment
-  3D-vertexing
-  B meson tagging

## The Pixel Detector

- 1.3 m

- Cross section  of barrel:

- 1.3 m

- In the nominal detector, 1744 modules overlap on the support structure to provide
-    hermetic coverage: 3 space points for |η|<2.5 for collisions up to 11 cm from nominal IP
- 3 barrel layers at r = 5, 9, 12 cm
- 2 x 3 disk layers
- Will be first large-scale active pixel device in operation
- 97.5% of pixels read out by dedicated preamp: 80 Million Channels
- 6.5 kW operating power in active volume, at 2V
- Detector will operate at -7°C.
- Cooling integrated into local support structure via thinned aluminum tubes, C3F8  evaporation.
- Total mass is 10% X0 normal to beam
- We may have to settle for a 2 hit system

## The Pixel Detector Module

- The Pixel Module consists of:
- Sensor: 2 cm x 6 cm x 250 μm n bulk silicon rectangle, with 47,268 n+ pixels; (most 50 x 400 μm)
- Pixels read out via 16 FE chips. 16 x 2880 charge sensitive preamp channels connected to sensor via bumping
- Module Control Chip (MCC): receives hits from FE channels, builds module-level events, communicates with “outside” world via “Type 0” cable
- Kapton flex circuit: routes signals between FE and MCC. Routes LV (2V, 1.6V) to chips and HV (150-600V) to sensor

- ~ 2 x 6 cm

-  Data is read out electrically from module via 1m “Type 0” cable @ up to 160 Mb/s
-  Data is converted between electrical and optical at far end of Type 0 cable

- Module on PCB support frame (lab use only)

## The Pixel Detector Module

- Sensor wafer
- 16 FE chipsBump-bonded onto sensor

- 50 μm pitch

- Solder bumps

- Final version of FE chip is “FE-I3”: 0.25 μm CMOS process, IBM
- First FE-I3 wafers dec’03. Typical yield 70%  extensive testing at wafer & chip level
- First FE-I3 Modules assembled January ’04

## Each channel of the FE chip has a charge-sensitive preamplifier with programmable threshold.  [+ a lot of nice bonus feature]
When the charge picked up by the FE channel from the pixel sensor exceeds the programmed threshold, the FE outputs the beam crossing ID and the Time Over Threshold (TOT)
Thresholds are measured in lab by repeatedly injecting a series of known test charges into a pixel’s preamp:

The resulting distribution is fit with an “s-curve”, which gives us the threshold and noise of the pixel

- When the charge picked up by the FE channel from the pixel sensor exceeds the programmed threshold, the FE outputs the beam crossing ID and the Time Over Threshold (TOT)
- Thresholds are measured in lab by repeatedly injecting a series of known test charges into a pixel’s preamp:
- The resulting distribution is fit with an “s-curve”, which gives us the threshold and noise of the pixel

- Lab Measurements of Modules

- threshold

- Noise

- No. times over threshold

- Injected charge

## Lab Measurements of Modules @ -10°C

-  Empirically, a module is usually stable with threshold set to > 10 x noise
-  We typically tune the modules to a threshold of 3000 e-
-  [A Minimum Ionizing Particle perpendicular to the sensor yields ~20 000 e-]

- FE-I3

- FE-I3

- Lab Measurements of Modules @ -10°C

- Typical threshold distribution

- Typical Noise Distribution:

- Precise threshold tuning takes 1h/module in the lab. FE-I3 features “auto-tune”, which does a good job in 30 seconds.

## Performance after irradiation

-  Extensive irradiation and test-beam programs have been carried out with previous   generations of Front End Chip.
-  No show stoppers seen, Modules still work well at ~ 50 MRad.

-  FE-I3 irradiation starting in one week, test beam later this summer
-  Only minor changes from FE-I2  FE-I3, so no change in rad. hardness expected

- Typical hit efficiency seen for MIP’s in testbeam:
- 99% before, 97% after irradiation

- FE-I2 irradiated to 60 MRad:

## Lab Measurements of Modules

- The preamp’s Time Over Threshold (TOT) is proportional to the ionization charge in the sensor.
- Low energy X-rays like to Compton-scatter, and their whole energy cango towards creating electron-hole pairs in the sensor
- Lab measurement with 60 keV X-ray source: expect 60k / 3.6 = 16.6k electron-hole pairs

- Single pixel

- Chip 5

-  Q (TOT) in a single pixel

- We correctly measured the X-ray energy!

- γ

## Lab Measurements of Modules

- 	[Charge injection measurements of thresholds mainly test the pixel’s preamp (they don’t directly involve the sensor]
- The X-ray measurements depend on a functional bump-bond between the sensor and FE-chip.
- Individual bump defects and “chip peal-off” are thus readily revealed by X-ray source measurements:

- (white pixels had no hits after module exposed to X-ray source for 1h)

## Production Testing of Modules

- The collaboration has just began more routine mass production and testing of FE-I3 modules. ~ 20 built & tested so far.
- About 13 hours of electrical testing + 48 hours thermal cycling / module.
- Testing 1744 modules is a huge effort
- Modules are ranked by quality, best ones are loaded onto local support structures (“sectors” and “staves”).
- Will flash some pictures of pre-production sectors in the time left...

- “Burn in”: Continuous
- operation & thermal
- cycling, +/- 30°C

- 48h hours

- initial electrical
- Tests,
- room temp

- 3 hours

- Repeat most initial
- Electrical tests,
- room temp

- Full electrical
- characterization,
- -10°C

- 2 hours

- 8 hours

## Pre-production Disk Sector (= part of endcap)

- back

- front

- Carbon fiber support plate

- Aluminum cooling tube

- Modules on front and back
- of sector overlap to provide
- full coverage

- empty

## IR Image of Disk Sector, power off

- Tchiller = 18oC

- Analog and Digital Power off

- M420005

- M420108

- M420015

## IR Image of Disk Sector, power on

- Tchiller = 18oC

- Analog and Digital Power on
- All three Modules configured & receiving Clock

- M420005

- M420108

- M420015

- TNTC= 22.4oC

- TNTC= 21.0oC

- TNTC = 24.0oC

## X-ray Image of Disk Sector

- up in coldbox

- LBL_13

- LBL_14

- LBL_16

- down in coldbox

- IZM

- AMS

- IZM

- Shadow
- of cooling
- tube

- LBL_4

- LBL_7

- LBL_3

- LBL_13

- LBL_14

- LBL_16

## Other activities

- A lot of ATLAS Pixel Detector work has been and is ongoing in areas that I did not describe today
- “Module component” production & production testing (FE & Sensor wafers, FE chips, MCC, flex, Type0 cable, etc.)
- Further integration of the detector
- Off-detector electronics
- Optical link
- Evaporative cooling
- Support structure
- Insertion tool
- Software

## Status Quo & Milestones Ahead

- After almost a decade of design, lab tests, irradiations & test beams...
- The FE chip design has been finalized with FE-I3
- Production of final-version ATLAS pixel modules has begun
- FE-I3 module loading onto local supports about to begin
- Irradiation of FE-I3 modules at CERN in one week
- Pixel test beam & ATLAS combined test summer ‘04
- All Pixel Detector components arrive at CERN by summer ‘05
- Installation of the Pixel Detector into ATLAS summer ‘06
- Startup of LHC & ATLAS in ‘07

## BACKUP SLIDES

## Production Testing of Modules

- The collaboration has just began more routine “mass” production and testing of FE-I3 modules
- After assembly, each module undergoes a large variety of electrical tests (threshold & TOT calibration, cross talk measurement, X-ray measurement, leakage current etc.)
- Due to the large number of channels, and limited parallel readout in our lab-setups, module-level electrical tests are among the more time-consuming part of the production chain:
- About 13 hours of electrical testing + 48 hours thermal cycling / module.
- Testing 1744 modules is a huge effort

- “Burn in”: Continuous
- operation & thermal
- cycling, +/- 30°C

- 48h hours

- initial electrical
- Tests,
- room temp

- 3 hours

- Repeat most initial
- Electrical tests,
- room temp

- Full electrical
- characterization,
- -10°C

- 2 hours

- 8 hours

## Several Institutes are involved in the module production. At LBL we are assembling and testing the disk modules.
The first Modules that may actually end up in ATLAS have just passed through the production chain:

Based on the electrical tests, the “best” modules will be loaded onto local supports (sectors and staves). 

- The first Modules that may actually end up in ATLAS have just passed through the production chain:
- Based on the electrical tests, the “best” modules will be loaded onto local supports (sectors and staves).

- Production Testing of Modules

- We are currently operating at 50-60% of our maximum production rate. (Without buying “more stuff”.)
- Although it’s a bit early to judge, my (personal) feeling is we are in good shape to get the work done in time.