Eric, thanks for the work. First let me clarify for everyone "why/is
it possible" for the CSPAM to be plugged into the STOP master even
though there is no CSPAM driven readout. Since several people have now
asked about this.
The first thing you need to understand is that the WFD is
automatically restarted on *every* event. A START signal is generated
at the end of the computer busy signal and if the WFDs aren't stopped
they will just ignore the START signal.
What this means is that in theory it would be perfectly acceptable to
STOP the WFDs on *every* event. After all, just because you STOP the
WFDs doesn't mean you have to read them out. All that really matters
is that is that if you STOP the system you restart it.
Now... Actually the way we cause the STOP is with the STOP-Master.
This unit generates a STOP (after a suitable delay) if one of its
inputs(one of a set of scintillator triggers) goes off. When we read
out an event we also read out the STOP-Master and it tells us what the
relative times between all the triggers in the event were.
The scheme which we use to decide when and what WFD channels to read
out is completely different and is implemented with a set of
CAMAC-List commands. So: is it necessary to plug in the CSPAM? No.
Is it OK? Yes. Why did we do it? It is an extra piece of information
(the time it took the CSPAM trigger to arrive relative to the other
triggers). I thought this extra piece of information(and redundancy)
would be useful. If people feel strongly that they want it unplugged
OK I don't really feel that strongly about it.
It doesn't have less jitters then other triggers(the ERP for example.)
The resolution is set by the 100ns clock of the STOP-Master itself.
So, in summary: There is no reason to unplug the CSPAM cable. The
fact that Eric measured 1.0 millisecond delay is interesting. Perhaps
the problem has gone away in more recent data. I copied a recent file
to Caltech today over the network to check this(run 10980). It took
about 5 hours and tonight I found out there seems to be no good
microvax 2 info in it. LGB didn't have this file in it for some
reason but I noticed that basically almost every event is a SM4 CIT
event on the first tank. What is going on? It looks like it might be
some sort of special calibration but it is not in the list.
In other news: I was able to see in this file that as Eric measured
the LIP input on the SM1 STOP-Master is fine. Apparently this problem
"fixed-itself" . Hmmm.... Ill try to get another file to look at the
2.5 usec thing. Eric send me the number of a good file before you
unplugged the CSPAM.
-Chris