Finding ST Sensors that cause CMN: A Follow up to TSC Meeting N. 215 Prof. J. Incandela UC Santa Barbara US CMS Tracker Project Leader Tracker Steering Committee Meeting Number 216 March 4, 2004 These slides were prepared with the help of Tony Affolder and are based upon work done this past week by the dedicated efforts of the UCSB production group

TSC No.216 March 4, J. Incandela 2 Is Increased Bias Current and CMN Correlated? As of TSC #215 held on Feb , UCSB had in stock 22 sensors which upon reprobing showed a current change of  I > 1.5  A These sensors were probed both at UCSB and U Rochester with uniform results (like many of those reported on this last tracker week) We ordered these sensors by increasing  I We built 8 modules with 9 of these sensors We picked every other sensor in the ordered list starting with the one with the lowest  I The sensor with large  I was always placed in position furthest from hybrid in module construction 1 module was built with 2 “bad” sensors 6 of 8 modules have common mode noise Of the two modules without common mode noise: The “bad” sensor had < 2  A of increased current Increased noise is seen around a known, and hence unbonded, pinhole The other module now has current consistent with QTC measurement after construction We expect ~11 of the 13 sensors remaining from the original 22 will cause CMN in modules

TSC No.216 March 4, J. Incandela Sensors Channels 442 at 80V Increased bias current seen at 60V in sensor reprobing

TSC No.216 March 4, J. Incandela Sensors Channels 203 at 70V Increased bias current seen at 30V in sensor reprobing 251 at 130V Increased bias current seen at 130V in sensor reprobing

TSC No.216 March 4, J. Incandela Sensors Channels at 150V Increased bias current seen at 250V in sensor reprobing

TSC No.216 March 4, J. Incandela Sensors Channels at 200V Increased bias current seen at 220V in sensor reprobing

TSC No.216 March 4, J. Incandela Sensors Channels 505,506 at 350V Increased bias current seen at 400V in sensor reprobing

TSC No.216 March 4, J. Incandela Sensors Channels 280, 281 at 250V Increased bias current seen at 250V in sensor reprobing

TSC No.216 March 4, J. Incandela 9 Updated Correlation Plot All CMN modules built at UCSB to date: 12 of 13 sensors with  I >3  A caused common mode noise 2 of 9 modules with  I between 2-3  A caused common mode noise

TSC No.216 March 4, J. Incandela 10 Conclusions The correlation is strong and it is at the same level first seen last summer. It is no fluke. It is therefore not at all difficult to identify affected sensors.