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GLAST Tracker: High-Efficiency Particle Detection System

The GLAST Tracker is a low-profile, modular, and redundant design particle detection system for the Gamma Ray Large Area Telescope (GLAST). It features precise track detectors, a segmented calorimeter, and a charged particle anticoincidence shield for enhanced background rejection. The tracker is designed to minimize multiple-scattering errors and self-veto at high energy.

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GLAST Tracker: High-Efficiency Particle Detection System

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  1. GLAST:Gamma Ray Large Area Telescope The GLAST Tracker and its assembly R.Bellazzini 1 Hamamatsu 27/03/2001

  2. GLAST Concept Low profile for wide f.o.v. Segmented anti-shield to minimize self-veto at high E. Finely segment calorimeter for enhanced background rejection and shower leakage correction. High-efficiency, precise track detectors located close to the conversions foils to minimize multiple-scattering errors. Modular, redundant design. No consumables. Low power consumption (580 W) Charged particle anticoincidence shield  Conversion foils Particle tracking detectors • Calorimeter • (energy measurement) e+ e- Pair-Conversion Telescope Photons materialize into matter-antimatter pairs: E -> me+c2 + me-c2 2 Hamamatsu 27/03/2001

  3. Tracker Grid Thermal Blanket ACD DAQ Electronics Calorimeter The Large Area Telescope (LAT) • Array of 16 identical “Tower” Modules, each with a tracker(Si strips) and a calorimeter (CsI with PIN diode readout) and DAQ module. • Surrounded by finely segmented ACD (plastic scintillator with PMT readout). • Aluminum strong-back “Grid,” with heat pipes for transport of heat to the instrument sides. 3 Hamamatsu 27/03/2001

  4. The LAT Hardware 4 Hamamatsu 27/03/2001

  5. One Tracker Tower Module Carbon thermal panel Electronics flex cables GLAST Tracker Design Overview • 16 “tower” modules, each with 37cm  37cm of active cross section • 83m2 of Si in all, like ATLAS • 11500 SSD, ~ 1M channels • 18 x,y planes per tower • 19 “tray” structures • 12 with 3% Pb or W on bottom (“Front”) • 4 with 18% Pb or W on bottom (“Back”) • 2 with no converter foils • Every other tray is rotated by 90°, so each Pb foil is followed immediately by an x,y plane of detectors • 2mm gap between x and y oriented detectors • Trays stack and align at their corners • The bottom tray has a flange to mount on the grid. • Electronics on sides of trays: • Minimize gap between towers • 9 readout modules on each of 4 sides 5 Hamamatsu 27/03/2001

  6. Tray assembling Carbon-carboncloseout • Trays are C-composite panels (Al hexcel core) • Carbon-fiber walls provide stiffness and the thermal pathway • from electronics to the grid. 6 Hamamatsu 27/03/2001

  7. Prototyping of the GLAST SSD Preserie HPK detector on 6’’ wafer Gained experience with a large number of SSD (~5% of GLAST needs) Additional Prototypes: Micron (UK), STM (Italy), CSEM (Switzerland) 7 Hamamatsu 27/03/2001

  8. Calendar Years 2010 2003 2000 2005 2002 2004 2001 Launch Inst. Delivery SRR I-CDR M-CDR I-PDR NAR M-PDR Implementation Ops. Formulation Inst. I&T Inst.-S/C I&T Build & Test Flight Units Build & Test Engineering Models Schedule Reserve SSD Procurement Ladder Production Tray Assembly Project schedule 8 Hamamatsu 27/03/2001

  9. Tests on preserie of final HPK SSD Comparison between HPK and GLAST results Measurements at Hiroshima U. (20), INFN-Pisa (10), SLAC (5) 9 Hamamatsu 27/03/2001

  10. Average tilt Planarity Tests on preserie of final HPK SSD Mechanics and dimension measurements Thickness Strip size = 64 ± 1 mm Pitch = 228.01 ± 0.01 mm Active width = 87557 ± 5 mm 10 Hamamatsu 27/03/2001

  11. Ladder assembly box Alignment Glueing 11 Hamamatsu 27/03/2001

  12. Ladder assembly Trasfer box Service box for bonding 12 Hamamatsu 27/03/2001

  13. Q/A during assembly • Acceptance tests (mechanics and leakage current @150V). • Leakage current after glueing the ladders. • Leakage current after bonding the strips. • Leakage current after encapsulation. • Leakage current after connection to the electronics. • Burn-in of individual strip with cosmic rays. • Complete set of tests (depletion voltage, bulk/interstrip and • decoupling capacitance, isolation resistors, leakage current • before and after irradiation,…) on test structures at the • batch level. • This strongly relies on detailed, stable and well documented tests made at the factory. 13 Hamamatsu 27/03/2001

  14. Alignment measurements Ladder assembly tools manufactured by G&A (Oricola, Italy). Precision of alignment within ± 8 mm 14 Hamamatsu 27/03/2001

  15. BTEM tray and tower assembly 15 Hamamatsu 27/03/2001

  16. Conclusions • R&D and specifications on SSD fully finished. • HPK pre-serie in full agreement with specifications. • Production of ladders can start in fall. • Production strategy strongly relies on mechanical tolerances • and Q/A tests made at the factory. • Production rates of 600-700 SSD per month are required • for more than one year. 16 Hamamatsu 27/03/2001

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