Recent TOB Developments

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 869 881 1010 1011 1013 1014 1015 1016 1030 1031 1038 1042 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.