1. GLAST LAT Silicon Tracker Marcus ZieglerIEEE 2005 1 The Silicon Tracker Readout Electronics of the Gamma-ray Large Area Space Telescope Marcus Ziegler Santa Cruz Institute for Particle Physics University of California at Santa Cruz GLAST LAT Collaboration ziegler@scipp.ucsc.edu Gamma-ray Large Area Space Telescope

2. GLAST LAT Silicon Tracker Marcus ZieglerIEEE 2005 2 GLAST LAT Tracker Overview e+e+ e–e–  Si Tracker 880 000 chanels 160 Watts The LAT Tracker is devided into: -16 Tracker Towers each stack is composed out of 19 trays Tray: Carbon-composite panel with Si-strip detectors on both sides. On the bottom side is a tungsten foil bonded

3. GLAST LAT Silicon Tracker Marcus ZieglerIEEE 2005 3 Tower

4. GLAST LAT Silicon Tracker Marcus ZieglerIEEE 2005 4 Electronics Packaging Kapton readout cables. Tested SSDs procured from Hamamatsu Photonics 19 “trays” stack to form one of 16 Tracker modules. Electronics and SSDs assembled on composite panels. 4 SSDs bonded in series. Composite panels, with tungsten foils bonded to the bottom face. 2592 10,368 342 648 342 18 Carbon composite side panels Chip-on-board readout electronics modules. Electronics mount on the tray edges. “Tray”

5. GLAST LAT Silicon Tracker Marcus ZieglerIEEE 2005 5 Detail of an EM MCM, at One End Nanonics Connector (will be Omnetics) Pitch-adapter flex circuit 90° radius GTRC ASIC GTFE ASIC Polyswitch Grounding screw hole Shown prior to wire-bond encapsulation and conformal coating.

6. GLAST LAT Silicon Tracker Marcus ZieglerIEEE 2005 6 Readout Electronics

7. GLAST LAT Silicon Tracker Marcus ZieglerIEEE 2005 7 Electronics Packaging  Dead area within the tracking volume must be minimized.  Hence the 16 modules must be closely packed.  This is achieved by attaching the electronics to the tray sides.  Flex circuits with 1552 fine traces are bonded to a radius on the PWB to interconnect the detectors and electronics. Detector signals, 100 V bias, and ground reference are brought around the 90° corner by a Kapton circuit bonded to the PWB. Composite Panel High thermal conductivity transfer adhesive PWB attached by screws Detector Readout IC Machined corner radius with bonded flex circuit.

8. GLAST LAT Silicon Tracker Marcus ZieglerIEEE 2005 8 Mechanical Structure  Carbon-fiber composite used for radiation transparency, stiffness, thermal stability, and thermal conductivity.  Honeycomb panels made from machined carbon-carbon closeouts, graphite/cyanate-ester face sheets, and aluminum cores.  High-performance graphite/cyanate-ester sidewalls carry the electronics heat to the base of the module.  Titanium flexure mounts allow differential thermal expansion between the aluminum base grid and the carbon-fiber tracker. SSDs Bias Circuits Tungsten Panel MCM Flexure Mounts Thermal Gasket Bottom Tray

9. GLAST LAT Silicon Tracker Marcus ZieglerIEEE 2005 9 Conclusions  Solid-state detector technology and modern electronics enable us to improve on the previous generation gamma-ray telescope by well more than an order of magnitude in sensitivity.  The LAT tracker design uses well-established detector technology but has solved a number of engineering problems related to putting a 900,000 channel silicon-strip system in orbit:  Highly reliable SSD design for mass production  Very low power fault-tolerant electronics readout  Rigid, low-mass structure with passive cooling  Compact electronics packaging with minimal dead area  We have validated the design concepts with several prototype cycles and are now approaching the manufacturing stage.  We’re looking forward to a 2007 launch and a decade of exciting GLAST science!