GLAST LAT Readout Electronics

Marcus Ziegler IEEE 2005 1

SCIPPSCIPP

The Silicon Tracker Readout The Silicon Tracker Readout Electronics of the Gamma-ray Electronics of the Gamma-ray Large Area Space TelescopeLarge Area Space Telescope

Marcus Ziegler

Santa Cruz Institute for Particle PhysicsUniversity of California at Santa Cruz

GLAST LAT Collaboration

ziegler@scipp.ucsc.edu

Gamma-ray Large Gamma-ray Large Area Space Area Space TelescopeTelescope

GLAST LAT Readout Electronics

Marcus Ziegler IEEE 2005 2

SCIPPSCIPPGLAST LAT Tracker OverviewGLAST LAT Tracker Overview

e+ e–

The LAT Tracker is divided into:

- 16 Tracker Towers

- Each stack is composed of 19 trays.

Tray:

- Carbon-composite panel

- Si-strip detectors on both sides

- On the bottom side of the tray, is glued an array of tungsten foils.

- Adjacent trays are rotated by 90o, with a 2mm gap in between, to form an x,y measurement plane.

GLAST LAT Readout Electronics

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SCIPPSCIPPOne Tracker TowerOne Tracker Tower

Requirements for GLAST:

Power < 200 W/channel

Efficiency > 98%

Noise occupancy < 5x10-5

Self triggering

Trigger rate up to 10 kHz

Minimal dead area

Minimize single point failures

GLAST LAT Readout Electronics

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SCIPPSCIPPCharacteristics of the Si-TrackerCharacteristics of the Si-Tracker

• 9126 Si-strip detectors from 6” wafers

• 74 m2 of Si (228m pitch)

• 884 736 readout channels

• 160 Watt power consumption

GLAST LAT Readout Electronics

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SCIPPSCIPPReadout SchemaReadout Schema

GTFE GTFE GTFE GTFE GTFE GTFE

GTRC

GTFE GTFE GTFE GTFE GTFE GTFE

GTRC

GTFE GTFE GTFE GTFE GTFE GTFE

GTRC GTRC

GTRC

GTRC

Data and trigger signalsControl signals

• 9 MCMs per side of the tower and 24 GTFE chips per MCM board • 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

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SCIPPSCIPPRight Angle InterconnectRight Angle Interconnect

GLAST LAT Readout Electronics

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SCIPPSCIPPDetail of an MCM, at One EndDetail of an MCM, at One End

Omnetics connector

Pitch-adapter flex circuit with 90° radius

GTRC ASIC

GTFE ASIC

Polyswitch

GLAST LAT Readout Electronics

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SCIPPSCIPPMechanical ChallengesMechanical Challenges

Flex Circuit

Internal Cu Planes

ASIC and Conductive Glue

Wire Bond

Encapsulation FillEncapsulation Dam

Fiberglass

Fiberglass Riser

• X-ray cross section of the edge of the MCM with the right angle 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 Ziegler IEEE 2005 9

SCIPPSCIPPSystem PerformanceSystem 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 a typical 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 32,000 electrons for a MIP passing through 400 m silicon.

Noise Occupancy:

The average fraction of channels above threshold at any snapshot in time.

For a typical integrated tracker module we measured a noise occupancy of 4.7x10-7

GLAST LAT Readout Electronics

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SCIPPSCIPPDetection efficiencyDetection 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 %

Hit efficiency

The overall efficiency was measured for each layer using cosmic-ray tracks.

We obtained efficiencies for the individual towers of about 99.6%

Inefficiency comes from dead channels and low fluctuations in the ionization.

GLAST LAT Readout Electronics

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SCIPPSCIPPPhoton event Photon event

GLAST LAT Readout Electronics

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SCIPPSCIPPCurrent statusCurrent status

All 16 tracker towers (TKR and CAL) are installed into the lat (next is ACD)

LAT integration completion in Jan 2006

Environmental testing at NRL until June 2006

Launch in August 2007