1. Recent TOB Developments
First LT failure and
Stereo Module Status
J. Incandela
With slides provided by E. Chabalina, A. Affolder, Dean White

2. Module 705 before LT
After assembly module was tested (09/08) on ARCS at 400 V and graded “B” (6 faulty channels). No problems observed.

3. Module 705: LT data
Data was taken at 20°C on Sept.19 (10 days after the first test). A group of high noise channels is seen around channel 219 and increased CMN is seen in chip #2

4. Module 705 after LT - I
Module was re-tested on ARCS on 09/23. High noise in channel #219 and high CMN is observed at 400 V. At 200 V channel #219 has only slightly higher noise than the rest of the channels

5. Module 705 after LT - II
On ARCS kept module at 400 V for 30 minutes before testing (to allow current settle down)
CMN did not go away, it became even higher

6. Comparison of IV curves
”before” measurement is taken on 09/08 on ARCS before LT
“after” measurement is taken on 09/23 on ARCS after LT
green curve is a measurement done using Keithley on 09/24 with 1 minute interval between steps
No visual defects are observed on the sensors around noisy channel #219
At this point we can’t conclude whether the effect we observe is due to thermocycling or if it is some other effect

7. Why be concerned
Several people have argued that this may not be a real problem for several reasons:
It is mainly occurring at high bias voltages
It causes only a small amount of Common Mode Noise (CMN)
The noise is removed by CMN subtraction in the FED.
In fact we see evidence that all of the above are false at significant levels.
It may be that more sophisticated CMN removal algorithms are needed and hopefully the FED is capable of running them
It may be that the new ST sensors have a drastic reduction in this problem
We will study 110 or so recent ST sensors sent to the US (thanks Manfred et al.) as soon as they clear customs.

8. CMN Turn-on Voltage

9. Common Mode Subtracted Noise
25 ADC
6.5 ADC
(Peak Off)
Modules with CMN (micro-discharge problem)
Common mode subtracted noise in blue
For majority of modules with problems, the CM subtraction is imperfect.
7 of 12 have >2.0 ADC noise
3 of 12 have more than twice the usual noise

10. Common Mode Subtraction Variation
Module 1010
Module 1016
Common mode subtraction results clearly vary
Answer differs mode-to-mode or test-to-test
Would yield varying signal efficiency/noise during data taking
Not clear how this will evolve with time/radiation

11. UCSB Stereo Module Production
UCSB Stereo plate completed on schedule
Tested via dry runs and produced results as good as the r-phi plates “right out of the box”
We made a fixture to attach the cable stiffener on our hybrids.
First hybrid retrofitted last week. Tested cable by making/unmaking connection 20 times by hand. No apparent problem with functionality and no signs of cracking.

12. First Stereo Module First Stereo TOB module made at USCB
Well within specs mechanically and functions very well
Kapton circuit was missing a trace for bias. We made it by hand with Ag Epoxy. Otherwise this is a Grade A module!
First TOB SS6 module to be made today.