Re: SM4 WFD

Charles Lane (lane@DUPHY4.Physics.Drexel.Edu)
Wed, 27 Sep 95 15:04:46 EDT

> While triggering the scope on the CSPAM input of the WFD STOP MASTER in
> SM4, I looked at the STOP input to the WFDs in SM4. The STOP was always
> arriving at 1000.1+-0.05 microsecs after the CSPAM. However, about
> 5% of the time, although CSPAM was firing (and the scope was triggering)
> I was not able to see the STOP signal coming out of the WFD STOP master.
> I don't think this has to do anything with the computer busy, as the
> CSPAM input to the STOP MASTER is already busy-veto'd (if the signal is
> taken out of the SPU) and definitely the dead time during calibrations
> is much less than 5%.

Sounds like a problem in the STOP MASTER. Maybe the previous event left
it in a state where it wouldn't issue another stop?

> I was wondering if the problem Chris is observing can be the result of having
> the CSPAM actually plugged into the WFD STOP MASTERs. Since CSPAM is
> neither setting the WFD_PATREG nor reading the WFD, I see no reason why
> CSPAM should be plugged into these modules (and thus creating STOPs).
> But if this fact is somehow related to Chris' observation, then I would
> expect this to be present throughout the whole detector.

I'd expect it too.

> I think we should eventually unplug the CSPAM inputs from the rest of the
> WFD STOP MASTERs *if WFD readout on CSPAM events is not going to be
> performed*.

As long as the FMT and HIPT inputs are still connected, okay!

If we are trying to trim the time-window for muons, it still might
be useful to have a CSPAM stop, because of the relatively small trigger
time jitter will allow a tighter window.

--
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