Puneeth Kalavase, UC, Santa Barbara

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Construction and Testing of CMS Rods

• Puneeth Kalavase, UC, Santa Barbara
• On behalf of US Tracker Outer Barrel group

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CMS Tracker
Outer Barrel (TOB)
Pixels
End Caps (TEC)
Inner Barrel Disks (TIB TID)
2,4 m
5.4 m
volume 24.4 m3 running temperature 10 0C
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Rods 101

• Rods Basic self-contained element of the TOB.

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Rods 101

• Carbon Fiber rod frames are built at Helsinki and
  shipped to CERN where communications and cooling
  infrastructure are incorporated. Then sent to US
  (FNAL and UCSB) where they are populated with
  modules and tested.
• Rods come in 3 flavors
• SS4 (Single Sided 4) - 6 modules each with 4
  readout chips (512 channels).
• SS6 (Single Sided 6) - 6 modules with 6 readout
  chips (768 channels).
• DS4 (Double Sided 4) - 12 modules with 4 readout
  chips, 6 of which are small angle stereo for
  better resolution in z direction.

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Tracker Outer Barrel (TOB)
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RODS
Communications Bus
AOH (Analog Optohybrid)
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Rod Assembly

• Rods are populated with sensors by engineers at
  both sites. Rate of rod assembly is 20-25
  rods/week at each site.

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Rod Testing

• Each rod put through preliminary 1 hour test in
  SRT (Single Rod Test stand). Basic functionality
  of Rods is tested.
• Perform Pedestal run in all 4 operating modes of
  readout chip and Charge Injection test in 2 of
  the 4 operational modes

Typical Pedestals
Typical Noise Profile
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Rod Testing

• Till now, most problems with the rods (new bad
  channels, communications failures, etc) have been
  found in SRT during our preliminary tests.
• After passing preliminary test, rods are tested
  in MRT (Multi Rod Test).
• MRT has capability to test up to 8 rods at one
  time.
• Goal is to push rods so that any weakness is
  discovered and fixed before integration in
  detector. Find possible pinholes, ie, weak
  coupling capacitors.
• MRT is a 2 day burn-in. We stress rods rods by
  cycling the temperature of the coolant from 20C
  to -23C. Run tests in both warm and cold.

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Rod Testing Multi Rod Stand
Lots of electrical, optical and cooling
connections!
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Bad Channel Flagging
Normalized Noise distribution has nice, tight
gaussian shape. Outliers are clearly visible and
can be easily cut on.
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Bad Channel Flagging
Plot of normalized Pulseheights response of
channel to charge injection Open Channels Noisy
Channels Shorts Pinholes (short in thin SiO2
layer, between AL strip and n-type bulk) would
show up here. Important to find pinholes because
they draw high current.
Bad modules are removed from rods and thoroughly
retested!
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Leakage Current
Monitoring Leakage Current is very important to
catch pinholes. Typical modules will have leakage
currents from 0.5-10 uA. If pinhole present,
current will be much higher.
uA
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Rod Production Status
On track to finish rod Production by mid summer
at the latest!
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Summary

• Module production is ramping down as we are
  almost done and the final step is to test and
  ship rods.
• Goal of testing is to stress rods and uncover any
  potential problems so that there are no surprises
  in detector. All problems encountered so far have
  been fixed.
• Production is going smoothly and rates are
  keeping pace with projected completion dates!
• Rods are being shipped to CERN for installation
  into TOB and final testing before integration
  with detector.