The D0 Silicon Microstrip Tracker D0SMT

1
The D0 Silicon Microstrip Tracker (D0SMT)

• Outline
• Design
• Detector Studies
• Coupling capacitors
• Radiation Damage
• LASER tests
• Electronics and readout
• Mechanical Assembly
• Production Testing
• Summary and prospects
• Installation in the spring of 2000

2
D0SMT Components

• Major SMT Subsystems
• Single Sided Ladder (3 chip)
• Double Sided 2o Ladder (9 chip)
• Double Sided 90o Ladder (6 chip)
• H Disk (SS back-to-back)
• F Disk (DS)

3
Barrel/Disk Module
4
H DISK

• Silicon IR 94.5 mm, OR 236 mm at wedge
  centerline
  
• Readout mounts on outer silicon detector
• Wedges alternate between two surfaces of a
  central cooling/support channel
  
• Effective stereo angle 15o

5
F Disk

• Silicon IR 26 mm, OR 105.27 mm at wedge
  centerline
  
• Readout mounts outboard of silicon, which allows
  disk to fit within a gap of 8 mm
  
• Wedges alternate between two surfaces of a
  centralcooling/support channel (beryllium)
  
• Effective stereo angle 30 degrees
• p-side Trace angle -15o with respect to wedge
  centerlinePitch 50 µm
  
• n-side Trace angle 15o with respect to wedge
  centerlinePitch 62.5 µm

6
Capacitor Studies

• In a double sided detector with grounded
  electronics, coupling capacitor breakdown will
  limit the lifetime of the detector.
  
• Studies
• Eliminate black hole effect in the SVX chip by
  bypassing parasitic transistor at the input (see
  VTX 96)
  
• Effect of wirebonding on capacitor breakdown
• 5-10 of capacitors fail at 50-100V after bonding
  (normally Vbd140V) on SS detectors
  
• No excess failures see on DS detectors with PECVD
  layer
  

7
n-side Capacitor Studies

• When electronics are connected to the n-side of a
  detector with shorted capacitors we see an
  anomalous current from the amplifier input
  
• Current is reduced when electronics is
  disconnected
  
• Effect seen on n-side only
• Caused by forward bias of the p-stop n junction

8
n-side Capacitor Studies
9
Irradiation Studies

• Expect 1 Mrad exposure for the inner layer per
  4fb1
  
• Irradiation with
• 8 GeV Protons from the Fermilab booster
• 1 MeV Neutrons (Lowell Mass.)
• Study
• Evolution of deletion characteristics
• Performance of detector and electronics

10
Irradiation StudiesCluster size
11
Irradiation Studiesnoise
12
H Disk Irradiation
Depletion voltage (volts)
Neutron fluence (1013/cm2)
Neff (1011/cm3)
Neutron fluence (1013/cm2)
13
Neutron Studies
Detector Studies using 1 MeV neutron source
14
Irradiation StudiesLASER Plateau
15
Detector Production

• Five detector types - 3-chip, 9-chip, 6-chip, F
  wedge, H wedge.
  
• All radiation testing complete
• laser and cosmic ray studies
• Measure in-situ rise times
• charge sharing distributions
• Probe testing
• 100 V capacitor breakdown test on each channel
• CV or alpha test to measure depletion
• IV Test
• Spot checks on
• Interstrip resistance
• Coupling capacitance
• Strip currents

16
Micron Detector Delivery
Needed for schedule
Needed for schedule
17
Readout System
18
D0SMT - Electronics

• SVXII Chip - done and tested
• Most issues involve bypassing and clock quality
• Needs careful hybrid(HDI) design
• HDIs - delivery pacing production
• Single layer flex 4 mil pitch, 2 mil vias
• Cables
• low mass, good frequency response (53 Mhz), low
  attenuation, no reflections, no radiation of
  clock signal to the calorimeter, fits in the
  allowed space.
• High impedance stripline
• 3 segments
• low mass section of varying length
• low mass fixed length
• high mass high quality section
• System tests underway now

19
Where we were burned

• HDI flex circuit - good prototypes but no good
  production circuits
  
• Find reliable company (Dyconex)
• pay extra
• Detector delivery - ordered detectors 2 years
  early but waited for BABAR, H1
  
• still a serious problem
• Cables
• low mass, high impedance striplines are
  difficult
  
• pay extra
• But we are now in production and expect to be on
  schedule

20
Mechanical Systems

• Design Philosophy
• Build planar assemblies (ladders, wedges, disks)
  precisely under (Zeiss) CMM
  
• Use mechanical tolerances to determine ladder
  placement in barrel (15 mm)
  
• Minimum Mass
• Be support structures
• Carbon fiber overall support

21
Ladder Assembly
22
Module Assembly
23
(No Transcript)
24
Ladder Assembly

• Match notches in Be support to posts in bulkhead
• 15 micron tolerance on Notched and posts
• 2 micron tolerances achieved in ladders

Detector fiducials relative to beryllium notches
Transverse offset from nominal (µm)
25
Rise Time Studies
Use LASER to excite SSD, Monitor preamp
26
Production Testing

• HDI Burn-in
• Encapsulation
• HDI Spot-check
• Ladder assembly
• Ladder Spot-check
• Ladder repairs
• Ladder burn-in
• LASER Test
• Insertion into detector

27
Laser TestingChannel uniformity
28
Laser TestingChannel Gains
29
Ladder and HDI
30
Summary

• We have achieved
• low mass flex/beryllium hybrids
• SVX II chip, 53 MHz readout
• Minimal dead area
• Precise construction
• A workable double sided design for moderate
  radiation doses
  
• Now we just have to build another 787,968
  channels