ATLAS SCT Endcap Detector Modules

Lutz FeldUniversity of Freiburg

for the ATLAS SCT Collaboration

Vertex 20025.6m

Vertex 2002 Lutz Feld, Freiburg University 2

Endcap Disks covered by 3 Rings of Modules

outer modules

inner modules

cooling block

power tapes

middle modules(on backside)

• 9 disks in each endcap, ~1.2m diameter CF structure

• 132 detector modules on a full disk, 1976 endcap modules in total

• modules have central mounting and cooling point module overlap easy

• each module serviced by a power tape and 3 optical fibres

• evaporative cooling circuits serve up to 13 modules

Vertex 2002 Lutz Feld, Freiburg University 3

3 Module Types

outer module(52 per ring)

inner module(40 per ring)

middle module(40 per ring)

Vertex 2002 Lutz Feld, Freiburg University 4

Endcap Module Design: Silicon Sensors

strip direction

strip direction

4 wedge shape silicon sensors

768 p-in-n strips,single sided

supplied by Hamamatsu and CiS

sensor alignment < 5µm

40mrad stereo angle

Vertex 2002 Lutz Feld, Freiburg University 5

Endcap Module Design: „Spine“

strip direction

strip direction

sensors are glued to „spine“:

TPG bar for heat removal(1700 W/m/K)

AlN wings for mechanical stability

mounting points and cooling contactsmounting points and cooling contacts

Vertex 2002 Lutz Feld, Freiburg University 6

Endcap Module Design: Hybrid

strip direction

strip direction

hybrid:flex circuit on carbon-carbon

hybrid connected to sensors only by fanins thermal split

12 ABCD3TAbinary read-out chips (DMILL)

Vertex 2002 Lutz Feld, Freiburg University 7

Hybrid

• development of hybrid was critical and needed several iterations

• very low impedance is key for successful operation of binary ABCD chips

• requirements:• double sided, 12 readout chips• supply well filtered analogue/digital power• com/data lines and drivers for optical link• detector bias supply (up to 500V)• heat removal (7W)• low mass

• implementation:• 6 layer copper/Kapton flex circuit• ~75µm feature size, ~3000 micro vias• flex folded around carbon-carbon

substrate• full assembly and basic testing in industry

Vertex 2002 Lutz Feld, Freiburg University 8

Thermal Performance of Endcap Module• evaporative C3F8 cooling system, capable to cool down to –30°C

• central module cooling block, split between hybrid and detectors,long modules have additional far end cooling block

• detailed simulations, confirmed by measurements of non-irradiated and irradiated modules on an evaporative cooling test rig

expected after 10 years expected after 10 years

inner module outer module

detector temperature vs. radiation damage for coolant at –21°C

Vertex 2002 Lutz Feld, Freiburg University 9

Electrical Performance• binary front-end chip occupancy vs. threshold „s-curves“

• signal height and noise are derived from „s-curves“

• relevant for operation: hit efficiency and noise occupancy

• noise occupancy determined by– front-end noise (fixed for given ASIC and detector)– channel-to-channel threshold variations (threshold trim per channel)– additional noise: common mode, feedback etc. (the difficult part...)

occupancy vs. channel and threshold occupancy vs. threshold

Vertex 2002 Lutz Feld, Freiburg University 10

16 Prototype Modules

• 9 outer, 2 middle, 5 inner

• modules built reliably inside

tolerances, in several institutes

• noise 1500 e or less

• noise occupancy @1fC: ~10-5

• gain ~50mV/fC

• threshold spread 150 e

ENC noise

threshold spread

gain

Vertex 2002 Lutz Feld, Freiburg University 11

System Test: 4 Modules on a Disk Sector

with 4 modules on disk

• no extra noise

• common mode noise negligible

noise for each chip when operatedsimultaneouslysingly

common mode noise

Vertex 2002 Lutz Feld, Freiburg University 12

Testbeam Results• binary read-out: efficiency and noise occupancy at given threshold

• spec: single hit efficiency > 99% while noise occupancy < 5E-4

• long modules before / after irradiation to 1.6 or 3.3 E14 24GeV-p/cm2

in a beam of 180 GeV pions

• 10 years LHC operation ~2.6 E14 p/cm2

• spatial resolution of 23µm achieved, as expected from pitch/sqrt(12)

non-irradiated@ 150V bias

1.6E14 24GeV-p/cm2

@ 480V bias3.3E14 24GeV-p/cm2

@ 480V bias

Vertex 2002 Lutz Feld, Freiburg University 13

Summary & Outlook

• ATLAS SCT endcap modules final design review in August 02

• now preparing for production of 2000 modules (+spares):– ASICs and detectors: ~80% delivered– hybrid: pre-series of 100 pieces in production, first samples delivered;

for production: full assembly and basic testing in industry– spines and fan-ins: pre-series in production, first samples delivered;

production can start soon

• module assembly and QA at 7 sites– good experience with assembly of prototype modules (>20)– preparation of production tooling and qualification over next months– production will take about 1.5 years