Athena module construction
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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. Unambiguous detection. Study of recombination. Longterm goal (2-3 years):

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ATHENA - Module Construction

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Athena module construction

ATHENA - Module Construction

P. Riedler, J. Rochet

Athena module construction


  • ATHENA is an experiment at the CERN antiproton decelerator (AD).

  • The first run took place in August 2000.


  • Antihydrogen production

  • Unambiguous detection

  • Study of recombination

Longterm goal (2-3 years):

CPT-test with a

precision of 10-12-10-15

(spectroscopy of 1S-2S)

Athena module construction

2. ATHENA Vertex Detector

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

2 x 511 keV g


Charged pions

Silicon strip detectors

CsI crystals + photodiodes

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

Athena module construction

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

Silicon Vertex Detector:

Strip detector design and design checks for 77K

Tendering and industry contact for production of silicon detectors

Testing and QA

Development of module design for 77K environment

Construction of all ATHENA silicon strip modules


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

Athena module construction

Schematic cross-section of the ATHENA vertex Detector

  • 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

Athena module construction

Outer layer

Athena module construction

Inner layer

Athena module construction

3. Modules

Athena module construction

4. Constraints

  • Double sided strip detectors

    • handling

    • connections on both sides required

  • Temperature range: 77 K-300 K

    • mechanical stability (different TEC) - BUS!

    • glue

  • Two layers of double sided detectors within 37.5mm radius

    • bonds

    • mounting

Athena module construction

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)

Athena module construction

5.1 Glue Deposit:

  • Reliable

  • Regular

  • Repeatable

Commercial glue dispenser


Alignment setup with microscope

Athena module construction

Alignment hole on the jig for


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

Athena module construction

  • Tests to define:

  • Duration

  • Needle diameter

  • Pressure

  • Step width

  • Weight



Always weigh the two components of the glue!

Athena module construction

5.2 Material matching

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)

Athena module construction

Tests with lN2

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

The silicon detectors did not break!!!

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

Athena module construction

Thermal expansion coefficients:

Capton~30 ppm/K

Alumine6.5-6.7 ppm/K

Glass D2637.2 ppm/K

Glass AF 454.5 ppm/K

Carbon2.1 ppm/K

Silicon2.6-4.2 ppm/K

(~40µ deviation)


Produced on 200mm Si wafer (400µ)

Chr-Al-Ti-Ni-Au on 10µ polyimide

(bonding tests!)



Athena module construction

6. Module Construction


<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

Athena module construction

1. Align first detector to setup

Athena module construction

2. Align second detector to referene line

measure deviation over full length

Distance piece for bus

Reference line

Athena module construction

3. Apply glue

Weigh the two components (Mettler-Toledo)

Athena module construction

4. Bus mounted

control if pads on detector and bus are well alined

mount fixation (recheck alignment)

Remove chuck from alignment station (store 24 hours)

Athena module construction

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

Athena module construction

5. Gluing jig for hybrids

Athena module construction

5. Bonding

Athena module construction

  • Built 37 modules in 24 days

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

  • Parallel work on the hybrid mounting


n+ implant edge

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