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User name saw
Log entry time 12:01:54 on March 17, 2011
Entry number 352282
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keyword=F1 reference time funIn 352266, in response to a question about what determines the timing of the reference time, Brad notes:
It should be the retimed L1A. You want the timing for gates, etc on the BigBite side to come from the particle in BigBite, not from the L1A which is timed off the HRS.If this is the case, then we can't determine time of flight relative to the HRS unless the HRS time is being recorded in the same TDCs that hold the retimed L1A reference time.
I would think that what we want is a reference time that has a timing determined by one particular HRS and that is easily correctable for HRS TOF, pulse height time walk, etc. Then the hodoscopes times are relative to the HRS and we can hope to see coincidence timing.
To illustrate, that the reference time is probably determined by a BigBite retiming, I show below the F1 reference time relative to the beginning of the F1 window for event type 3 and event type 5. (Event types 1,2, and 4 look just like the event type 3 plot) These plots are possible to make, because the F1 data header word contains the time of the beginning of the F1 window, albeit with a poor (7ns) resolution.
To me, it looks like the reference time is random relative to the common stop going to the F1s, and that the retiming circuit piles up stuff at the edges of the coincidence window. Presumably, HRS/bigbite coincidences lie between peaks. I don't know the meaning of the extra peak in the event type 5 picture. I suppose it could be coincidences with an HRS, but maybe it is just a funky retiming.
F1 reference time for event types 1-4
F1 reference time for event type 5
