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User name R. Michaels
Log entry time 16:28:54 on July 2,2010
Entry number 329461
This entry is a followup to: 329213
keyword=comments on coincidence measurements
This log entry tries to anticipate the TDC spectrum we'll
be looking at for finding coincidences. I don't think anyone
has thought about this.
An early activity will be to find true e- pi+ coincidences to
verify the timing setup.
We'll be looking at the "trigger flags".
Triggers are defined in halog 329213 and 329311
Triggers were plugged into a TDC to make trigger flags,
see halog 329275
What we may see is shown in fig 1 for the trigger on the two
Since we aligned all the triggers at the trigger supervisor, it's
not obvious which one will define the timing for the true coinc-
dences. If we aligned perfectly, then the time gap "TG" in fig 1
would be zero. I expect TG to be between 0 and 10 nsec. The
"true coincidence" peak will be bigger or smaller depending on
the signal-to-background ratio.
Note, there are variations on this. In the "scope picture", B
could be earlier than A. This means that A defines the coincidence
timing. This would reverse the roles. The common stop for the TDC
comes from whatever made the timing at the TS.
Also, this picture assumed that ps1 = ps3 = ps4 = 1.
In the more common case where ps1 and ps3 are large, the self-timing
peak will occur on the left side for each of T1 and T3.
Anyway, we'll have fun sorting out what the peaks mean.