[d2n-analysis-talk] BB trigger timing

[posik at jlab.org]

Hi Brad,

  So I am going over the trigger diagrams at

https://hallaweb.jlab.org/wiki/index.php/DAQ_Diagrams

I guess my first question is with the first trigger diagram, the one titled
"Trigger Timing at the BigBite Weldment"

What is the Big Bite weldment? Is this the spot where the T1 is actually
formed, meaning that TDC shower sums generated a T1?

I have written some things over the image of the trigger diagrams that I
am looking at. For the first diagram refer to trigger_dia_1.png.

 Taking now T1 as an example I see that there is a time on the arrow after
the T1 trigger, I assume that this is just the time delay that the wire
introduces to the T1 for the first wire (154 ns). It then goes to PS707,
which I think is discriminator. Then a PS754. I have a list of the
different components used and it says that this is a Quad Logic. I Do not
know what this is, but there is two outputs from this unit. One goes into
forming the T5 and the other goes to NIM-ECL LT. Could the PS707 be
acting as a sort of splitter? I also do not know what the NIM-ECL LT
does.

 So if I add up the timing of the wires, then does that mean that the T1
reaches the Trigger supervisor 174 ns ? Also I was wondering if you knew
the resolution of the Big Bite TDCs (1881's). Looking at the scintillator
db files, I seen 35ps/chan, however I do not know how correct this is.


Now the second trigger diagram at

https://hallaweb.jlab.org/wiki/index.php/DAQ_Diagrams

titled "Re-timing at the Big Bite Weldment" deals with the L1A from the
trigger supervisor and re-times it. For this part I will refer to
trigger_dia_2.png. We have our L1A which goes to ECL-NIM LT unit and then
to the PS754. The signal is then split to a LC222 and a PS754. I think the
LC222 is a gate delay generator, and is responsible for forming a large
L1A gate? The large L1A gate is then compared to the T6 gate and this is
what is responsible for forming the re-timed L1A?

There are three inputs listed in a dotted box below this "Re-timing at the
Big Bite Weldment" diagram and I was wondering if how I have them labeled
in red in the trigger_dia_2.png image is correct?

Thanks
Matt

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