When I fixed the Common Strobe (CS) delay yesterday so that it came
after the Physics Trigger (PT), I added too much delay (20ns?) so the CS
was COMFORTABLY after the PT. But this means the start to the TDC is
20ns later, and so likely the stop signals for the bottom tubes are too
close (45ns is the LeCroy-recommended minimum) to the start. Looking on
the scope at the tube signal inputs to the TDC, the bottom tubes do seem
to be a bit earlier than the top, by something less than 10ns.
I've changed the CS so it is around 12ns after the PT (which is really
too close when we run protons), TDCs should be ok now.
Karen Dow
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