Hiroyasu Tajima Stanford Linear Accelerator Center VERTEX 2005 November 11, 2005 Chuzenji-lake, Japan GLAST Tracker Woodblock print by Hasui Kawase Kegon fall Chuzenji lake

GLAST Tracker, H. Tajima, VERTEX 2005, NOV. 11, 2005 Outline Overview of GLAST Tracker.  Requirements.  Mechanical and electronics design. Production.  Alignment.  Production issues. Performance.  Bad strips, hit efficiencies.  TOT calibrations.  Threshold, trigger dispersions.  Transient noise issues. Current Status and Future Schedule.

GLAST Tracker, H. Tajima, VERTEX 2005, NOV. 11, 2005 GLAST/LAT Collaboration Gamma-ray Large Area Space Telescope Stanford University & Stanford Linear Accelerator Center NASA Goddard Space Flight Center Naval Research Laboratory University of California at Santa Cruz Sonoma State University University of Washington Texas A&M University – Kingsville Ohio State University Commissariat a l’Energie Atomique, Saclay Ecole Polytechnique, College de France, CENBG (Bordeaux) Hiroshima University Institute of Space and Astronautical Science University of Tokyo Instituto Nazionale di Fisica Nucleare Agenzia Spaziale Italiana Instituto di Fisica Cosmica, CNR Royal Institute of Technology, Stockholm Stockholms Universitet

GLAST Tracker, H. Tajima, VERTEX 2005, NOV. 11, 2005 GLAST/LAT Overview Satellite experiment to observe gamma-try from Universe.  Wide energy range: 20 MeV – 300 GeV  Large effective area: > 8000 cm 2 (5xEGRET)  Wide field of view: > 2 sr (4xEGRET) Scientific objectives.  Dark matter. Neutralino annihilation.  Particle acceleration. Cosmic ray origin Pair-conversion telescope.  “Clear” signature.  Background rejection.  e+e+ e–e–

GLAST Tracker, H. Tajima, VERTEX 2005, NOV. 11, 2005 Instrument Configuration Tracker: conversion, tracking.  Angular resolution is dominated by scattering.  Converter thickness optimization. Calorimeter: energy measurement.  8.4 radiation length.  Use shower development to compensate for the leak. Anti-coincidence detector:  Efficiency > 99.97%. Si Tracker 90 m 2, 228 µm pitch ~0.9 million channels CsI Calorimeter 8.4 radiation length Anti-coincidence Detector Segmented scintillator tiles 99.97% efficiency e+e+ e-e- 

GLAST Tracker, H. Tajima, VERTEX 2005, NOV. 11, 2005 Requirements for Tracker Conversion Efficiency > 58%. Aspect (H/W) ratio < 0.45 (for wide field of view). Active area > 19,000 cm 2 (Fraction > 88%). 6-in-a-row tracker trigger.  Efficiency > 90%.  Single layer trigger rate < 50 kHz.  Trigger jitter 0.5 MIP. Threshold dispersion < 10%. Noise data volume: 40 noise hits per event.  Average Noise occupancy < 5x Hit efficiency > 98% Dead time < 10% for 10 kHz. Power consumption < 160 W. Survival temperature range: -15 – 45 °C. Careful for what you wish in NASA project.

GLAST Tracker, H. Tajima, VERTEX 2005, NOV. 11, 2005 Mechanical Design Readout Cable Multi-Chip Electronics Module (MCM) 2 mm gap 19 Carbon-Fiber Tray Panels Titanium Flexure Mounts Carbon-Fiber Sidewalls (Aluminum covered) Silicon Strip Detectors 18 X-Y Pairs of Planes “Thin” Tungsten Foil (3% X 0 ) 12 Locations “Thick” Tungsten Foil (18% X 0 ) 4 Locations No Tungsten Foil 2 Locations 1 X 2 Y 3 X 4 Y 18 Y 17 X 16 Y 0 Y 5 type of trays.

GLAST Tracker, H. Tajima, VERTEX 2005, NOV. 11, 2005 Tray Structure Silicon Strip Detectors Bias Plane Tungsten Foil Multi-Chip Module Top Layer Wire Bonds Multi-Chip Module Bottom Layer Structural tray panel: C-C machined closeout frame Aluminum honeycomb core CFRP face sheets Microbonding

GLAST Tracker, H. Tajima, VERTEX 2005, NOV. 11, 2005 Readout Electronics Architecture GLAST Tracker Readout Controller (GTRC) 9 GTRC per cable. Communication between 24 GTFE and back-end electronics. TOT measurement from layer-OR trigger signal Emphasis on compactness, minimum of wiring, and redundancy: Serial, LVDS readout and control lines on flat flex-circuit cables. Any single component (GTFE, GTRC, cable) can fail without affecting the other.

GLAST Tracker, H. Tajima, VERTEX 2005, NOV. 11, 2005 Tracker Front-end Electronics GTFE (GLAST Tracker Front-end Electronics) ASIC  Preamplifier - shaper - discriminator  One threshold DAC and one calibration DAC per chip.  64 channels per chip, 24 chips per MCM.  Noise: ~1500 e for 4 SSD ladder.  Gain: ~100 mV/fC.  Peaking time: 1.5 µs.  0.1 mW/channel. GTFE GTRC

GLAST Tracker, H. Tajima, VERTEX 2005, NOV. 11, 2005 SSD SSD reference crosses 8.95 cm 8.95 cm x 8.95 cm. 226 µm pitch. 400 µu thick. Manufactured by HPK. 10,368 wafers. 0.5% rejection fraction. 2.5 µm dicing accuracy. INFN/Pisa

GLAST Tracker, H. Tajima, VERTEX 2005, NOV. 11, 2005 Ladder and Tray Assembly Ladder Assembly  Take advantage of excellent dicing accuracy.  Manual alignment.  Precise SSD alignment within ladder.  No CMM required. Tray Assembly  20 µm ladder placement accuracy. INFN/Pisa

GLAST Tracker, H. Tajima, VERTEX 2005, NOV. 11, 2005 Tower Assembly Alignment pin ~1m 8 type of cables due to space constraint Stacking trays Attach cables Side panel

GLAST Tracker, H. Tajima, VERTEX 2005, NOV. 11, 2005 Tray Alignment by Muon Track X4 X3 X2 X1 X0 real position ideal position res =  x +  z · cot(θ) θ horizontal displacement: 157  m vertical displacement: 81  m MC Data after alignment Residual rms = 137  m Residual rms = 124  m Scattering dominant INFN/Pisa

GLAST Tracker, H. Tajima, VERTEX 2005, NOV. 11, 2005 Production Issues Delamination due to thermal-vacuum cycles.  Kapton bias circuit. Extremely difficult to glue tungsten. Polymer coating of tungsten.  Wire-bonding encapsulation. Silicone contamination from pitch-adapter bonding process. - Eliminate use of silicone based tape. SSD movement due to CTE mismatch of tungsten foil. -Eliminate encapsulation for SSD wire-bonding. -Reduce thermal excursion. Pitch-adapter cracking.  Silent modification of Ni plating process. Flex circuit delivery delays.  Incompetent vender. MCM PWB ASIC Pitch-adapter flex bonded over radius Adhesive Kapton Bias Circuit

GLAST Tracker, H. Tajima, VERTEX 2005, NOV. 11, 2005 Flight Module Delivery All flight modules are delivered and integrated.  Flex cable delivery has been bottle neck. ACD is being integrated. Total Monthly

GLAST Tracker, H. Tajima, VERTEX 2005, NOV. 11, 2005 Hot and Dead Strips Hot strip definitions.  Data mask. Mask noisiest strips to satisfy 5x10 -5 average occupancy. 7 masked strips.  Trigger mask. Mask noisiest strips to satisfy 50 kHz layer trigger rate. Dead strips Mean: 0.8 / layer Hot strips Mean: 0.7 / layer 1%

GLAST Tracker, H. Tajima, VERTEX 2005, NOV. 11, 2005 Disconnected Strips.  Broken pitch adapter.  Disconnected wire-bond between MCM and SSD.  Disconnected wire-bond between SSDs. Broken ladder strips Mean: 4.4 / layer Disconnected strips Mean: 3.0 / layer 1%

GLAST Tracker, H. Tajima, VERTEX 2005, NOV. 11, 2005 Hit Efficiencies Specification: hit efficiency > 98%.  99.0% of layers satisfy the specification.  Average efficiency: 99.6%.  2%

GLAST Tracker, H. Tajima, VERTEX 2005, NOV. 11, 2005 TOT/Calibration DAC Calibration TOT gain is calibrated for each channel. Use MIP signals to calibrate “calibration” DAC. With gain correction Without gain correction ~30% rms ~8% rms

GLAST Tracker, H. Tajima, VERTEX 2005, NOV. 11, 2005 Trigger Jitter Trigger jitter important for ACD veto.  Trigger time walk due to input charge is dominant source of trigger jitter.  Specification: Trigger jitter 0.5 MIP.  Proper threshold setting necessary. Specification Trigger timing for 0.5MIP

GLAST Tracker, H. Tajima, VERTEX 2005, NOV. 11, 2005 Threshold Dispersion Trigger threshold.  Threshold at pulse peak.  Dispersion: 5.9%. (within chip: 5.2%, chip-to-chip: 2.7%). Threshold for data capture.  Strip data is captured ~2 µs after trigger request.  Larger dispersion due to variation of fall time.  Dispersion: 12.0%. (within chip: 8.3%, chip-to-chip: 7.0%). ~2 µs

GLAST Tracker, H. Tajima, VERTEX 2005, NOV. 11, 2005 Transient Noise Issue 6 layers out of 612 layers exhibit transient noise.  Infrequent (0/day – a few/hour).  Confined within one ladder.  Noisy ladder different episode to episode.  Many strips are affected at the same.  No apparent dependence on bias voltage or vacuum. No major effect on operation.  Trigger rate, occupancy within specification on ground. Occupancy time profileLayer-OR time profile Strip profile

GLAST Tracker, H. Tajima, VERTEX 2005, NOV. 11, 2005 Current Status and Future Schedule All flight detector modules are delivered.  Tracker meet all specifications. DAQ integration and online software test.  Now – Jan Environmental test at NRL.  Feb – June Beam test at CERN(?)  Spare modules.  Proposal in preparation.  ~ June Space craft integration. Launch from Kennedy SFC.  Sep  Largest Silicon Detector in the Space. Spitzer Telescope Launch on a Delta II Heavy (near Earth)