ATHENA - Module Construction

P. Riedler, J. Rochet

1. ATHENA

• ATHENA is an experiment at the CERN antiproton decelerator (AD).• The first run took place in August 2000.

Goals:

•Antihydrogen production

Longterm goal (2-3 years):CPT-test with a precision of 10-12-10-15

(spectroscopy of 1S-2S)

•Unambiguous detection

•Study of recombination

A detector system surrounds the recombination zone to detect H via its annihilation signals:

Charged pions2 x 511 keV “back-to-back”

Silicon strip detectors CsI crystals + photodiodes

Determine the charged vertex and check the collinearity of the 2 within a time-window (~1µs).

2. ATHENA Vertex Detector

Petra’s activities (Nov. 1998-March 2001) in ATHENA:

Silicon Vertex Detector:

Strip detector design and design checks for 77KTendering and industry contact for production of silicon detectorsTesting and QA Development of module design for 77K environmentConstruction of all ATHENA silicon strip modules

Beamcounter:

Development of ultra-thin silicon beamcounter (6-67µm) for 5.3MeV antiprotons at 10K (5x107 mips per µm)

• Cylindrical symmetry• Outer diameter: 139.7 mm• Inner diameter: 75 mm• Length: 241.1 mm

• Temperature: 77K• Vacuum: 10-7 mbar

• 16-fold symmetry

• 2 layers Si strip-detectors •192 CsI crystals with Si photodiodes

• 8960 read-out channels

Schematic cross-section of the ATHENA vertex Detector

Outer layer

Inner layer

3. Modules

4. Constraints

• Double sided strip detectorso handlingo connections on both sides required

• Temperature range: 77 K-300 Ko mechanical stability (different TEC) - BUS!o glue

• Two layers of double sided detectors within 37.5mm radiuso bondso mounting

5. Gluing and matching of the module components

Glue: araldite W106 low temperature mixture (50:50)(Advice from the group of M. Hominal at CERN)

Temperature cycling (300K-77K-300K)

• Reliable • Regular• Repeatable

Commercial glue dispenser+

Alignment setup with microscope

5.1 Glue Deposit:

Final setting glue drop for 18s every 10.6mm, 3bar N2

Alignment hole on the jig for needle

Tests to define:• Duration• Needle diameter• Pressure• Step width• Weight

SiliconGlas

Always weigh the two components of the glue!

Production of prototypes:

Prototype 0: 160 mm Si + PCB hybrid + capton (V0) Prototype 1: 162 mm Si + alumine hybrid + alumine bus (V1)Prototype 2: 162 mm Si + alumine hybrid + glass (D263) bus (V1)Prototype 3: 162 mm Si + alumine hybrid + alumine bus (V1)Prototype 4: 162 mm Si + alumine hybrid + glass (AF45) bus (V1)Prototype 5: 162 mm Si + alumine hybrid + carbon bus (V1)Prototype 6: 162 mm Si + alumine hybrid + silicon bus (V1)

5.2 Material matching

Tests with lN2

Alumine bus - prototype module seen from the side at lN2 temperature

Glass bus - prototype module seen from the side at lN2 temperature

The silicon detectors did not break!!!

Thermal expansion coefficients:Capton ~30 ppm/KAlumine 6.5-6.7 ppm/KGlass D263 7.2 ppm/KGlass AF 45 4.5 ppm/KCarbon 2.1 ppm/KSilicon 2.6-4.2 ppm/K(~40µ deviation)

Bus:Produced on 200mm Si wafer (400µ)Chr-Al-Ti-Ni-Au on 10µ polyimide(bonding tests!)Laser-cutting NEW!

Precision:<100µm over the full detector length required (164 mm)Align the detectors to one reference line on one jig no alignment in z required!Microscope reference: n+ implantation edge

6. Module Construction

1. Align first detector to setup

2. Align second detector to referene line measure deviation over full length

Distance piece for busReference line

3. Apply glue Weigh the two components (Mettler-Toledo)

4. Bus mountedcontrol if pads on detector and bus are well alinedmount fixation (recheck alignment)Remove chuck from alignment station (store 24 hours)

Cals put onto lense-paper on top of the bus (1.125 kg)

5. Gluing jig for hybrids

5. Bonding

• Built 37 modules in 24 days

• 1-1.5 hours work on the alignment setup per module

• Parallel work on the hybrid mounting6

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Entries

100806040200Misalignment from (0/0) [micron]

(0/0)n+ implant edge