CDF RUN II COMMISSIONING

Mitigation of the problem by reducing the DVDD current and DVDD current swing.

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All the theories that came up during the investigatiosn are consistent with the fact that the failure mode (yet to be understood) could be mitigated by reducing the DVDD current and the DVDD current swing

Some work has started in this direction. There are basically 4 ways to minimize the current and the current swing:

current.mpg 11 MB - Short movie (40 seconds) showing how the amplitude of the oscillation changes when the current through a pair of wire-bonds is ramped up from 13 to 20 to 30 to 40 to 50 to 60 to 70 to 80 mA with a step every 5 seconds.  THIS IS TO EXPLAIN THE POTENTIAL MITIGATION ACHIEVABLE BY LOWERING THE RDRIVER SETTINGS

occupancy.mpg 4 MB - Short movie (15 seconds) showing how the width of the current pulse affetc the amplitude of the oscillations. The current pulsed is lowered from 8 to 5 to 3 us with a step every 5 seconds  THIS IS TO EXPLAIN THE POTENTIAL MITIGATION ACHIEVABLE BY LOWERING THE OCCUPANCY

Here are the results of the scans of DVDD current swing versus occupancy (PHI and Z) and RDriver setting as performed by Reid, Julia and Steve.

3 different R-Driver settings have been already tried in CDF with the real silicon detector. The results are summarized in this Table from Jason. Still from Jason here is a more detailed analisys

Here is a link to the studies that show efficiencies vs read-out thresholds. This work was done by the Silicon Studies Group. We now have a conservative readout threshold of 7 and we are going to raise it to 9 today (10/30/2002).
 
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Last Updated Oct 30, 2002 by Gino Bolla
Gino Bolla