GLAST LAT Readout Electronics Marcus ZieglerIEEE SCIPP 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 Gamma-ray Large Area Space Telescope

GLAST LAT Readout Electronics Marcus ZieglerIEEE SCIPP GLAST LAT Tracker Overview e+e+ e–e–  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 if the tray is an array of tungsten foils glued that match the active area of the detectors. -Trays are rotated by 90 o to form an x,y plane with a 2mm gap in between.

GLAST LAT Readout Electronics Marcus ZieglerIEEE SCIPP Tower Requiements: Power < 200  W/channel Efficiency > 98% Noise occupancy < 5x10 -5 Trigger rate 10 kHz Minimize single point failures

GLAST LAT Readout Electronics Marcus ZieglerIEEE SCIPP Readout Schema All front end chips can be programmed at any time from both sides The layer OR is used as a trigger primitive (6 layer in a row form the usual tracker trigger) The strip hits can be latched in one of the four GTFE readout buffers and be read out to both sides Measure of the deposited charge by counting the clock ticks the layer OR is high

GLAST LAT Readout Electronics Marcus ZieglerIEEE SCIPP Detail of an MCM, at One End Omnetics connector Pitch-adapter flex circuit with 90° radius GTRC ASIC GTFE ASIC Polyswitch

GLAST LAT Readout Electronics Marcus ZieglerIEEE SCIPP Mechanical Challenges Flex Circuit Internal Cu Planes ASIC and Conductive Glue Wire Bond Encapsulation Fill Encapsulation Dam Fiberglass The “Cliff” X-ray cross section of the edge of the MCM with the right angel interconnect. 1-layer Kapton flexible circuit that is glued over 1mm radius machined into the edge of the polyimide-glass PWB.

GLAST LAT Readout Electronics Marcus ZieglerIEEE SCIPP System Performance Power consumption: A low (<200  W / channel) power consumption was achieved by keeping the amplification and digitization schemes very simple. -> The power consumption of one tracker tower during data taking is measured to be 9.9 W Noise Performance: The shaper output peaking time is about 1.5  s. For 36 cm long Si strips (about 41 pF load) the noise charge is about 1500 electrons. The most probable signal is electrons for a MIP passing through 400  m silicon. Noise Occupancy: The average fraction of channels above threshold at any snapshot in time. For an integrated tracker module we measured a noise occupancy of 4.7 x 10 -7

GLAST LAT Readout Electronics Marcus ZieglerIEEE SCIPP Detection efficiency The fraction of active area within one plane of 16 SSDs is 95.5 % Taking into account the dead area between the towers the active fraction of the over all tracer is 89.4 % Inefficiency comes from dead channels and low fluctuations in the ionization. The overall efficiency was measured for each layer using cosmic-ray tracks. We obtained efficiencies for the individual towers of: 98.6%, 99.6%, 99.5%, 99.6%, 99.4%, 99.6%, 99.7%, 99.6%, and 99.7%

GLAST LAT Readout Electronics Marcus ZieglerIEEE SCIPP Threshold and Gain Uniformity Threshold measurements from a typical single MCM. The measurements were made by fitting threshold scans from an internal-charge-injection run. The injected charge corresponded to about 1.5 fC (0.29 MIPs).

GLAST LAT Readout Electronics Marcus ZieglerIEEE SCIPP Current status All 16 tracker towers are integrated into the grid