Bob has plots of the average t0 for scintillators in each TDC, both west and east. You can see that the t0 varies in a consistent way, except of course for the pair of TDCs that show the large jump. The jump occurs at about the same time that the east side had its TDCs replaced with the new revision and the west side received some east side TDCs. We think that the west side TDC showing the jump received the problematic east side TDC.
The next page shows the BMU crossing times, which show the same variation, albeit at with a much smaller variation. The last page (4) shows the average crossing time on west and east, and you can clearly see the same pattern as in the scintillators. In addition, you can see the east settles on a crossing time 2 nsec earlier than the west. This time difference has been known for a long time.
Since this same pattern pertains to both scintillators and wires, and to both west and east, I think we can conclude that the origin is upstairs and has nothing to do with our preamps or pulse shaping in the collision hall. If this is a problem with the timing pulse fanned out to the TDCs in a crate, it has to originate back at the pulse generator. In that case other systems should see the same effect.
Modified 26-July-2004 at 10:34
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