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ATHENA - Module Construction

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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  1. ATHENA - Module Construction P. Riedler, J. Rochet

  2. 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): CPT-test with a precision of 10-12-10-15 (spectroscopy of 1S-2S)

  3. 2. ATHENA Vertex Detector A detector system surrounds the recombination zone to detect H via its annihilation signals: 2 x 511 keV g “back-to-back” 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).

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

  5. 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

  6. Outer layer

  7. Inner layer

  8. 3. Modules

  9. 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

  10. 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)

  11. 5.1 Glue Deposit: • Reliable • Regular • Repeatable Commercial glue dispenser + Alignment setup with microscope

  12. Alignment hole on the jig for needle Final setting glue drop for 18s every 10.6mm, 3bar N2

  13. Tests to define: • Duration • Needle diameter • Pressure • Step width • Weight Silicon Glas Always weigh the two components of the glue!

  14. 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)

  15. 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

  16. Thermal expansion coefficients: Capton ~30 ppm/K Alumine 6.5-6.7 ppm/K Glass D263 7.2 ppm/K Glass AF 45 4.5 ppm/K Carbon 2.1 ppm/K Silicon 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!

  17. 6. Module Construction 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

  18. 1. Align first detector to setup

  19. 2. Align second detector to referene line measure deviation over full length Distance piece for bus Reference line

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

  21. 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)

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

  23. 5. Gluing jig for hybrids

  24. 5. Bonding

  25. Built 37 modules in 24 days • 1-1.5 hours work on the alignment setup per module • Parallel work on the hybrid mounting (0/0) n+ implant edge

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