Tancredi,
Actually the TDCs that were dropping below the 45ns minimum were the
big TOFs, not the small paddles. When including the small paddles in
the trigger as substitutes for big TOFs, it's not clear to me what
determines the timing. We're in Common Strobe (CS) mode, where the CS
is the OR of the meantime of all the left "TOF"s. Since the small
paddles have short transit times, I suppose one of them determines the
timing of the CS. That means the TDC start will be EARLIER than in our
usual configuration, no?
Maybe the short transit times in the small paddles explain why we have
to check/change the CS delay compared to the physics trigger(PT),
whenever we switch the trigger from cosmics to efficiency check to
flasher.
The solution is to look at the scope, make sure the CS is after the
PT. And then look at the TDC start compared to the individual tube TDC
stop signals, make sure the time diff is more than 45ns.
At some point (after we get wider pulses out of the MLU so we can have
the CS more than 10ns after the PT) maybe we will need to replace the
TDC stop cables with longer ones, or maybe not. The 11ns I took out of
the TDC start might just be enough.
Karen
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