[Halld-tagger] first results on fiber light yields

[Alexander Somov]

Hello Richard,

> | Why 2) is about 20% wider (was it a different readout channel)?
> Because it runs through 100ft of cable, whereas 1 and 3 run through 50ft of
> cable.
>
> | (there could be some sampling effects due to the different pulse
> | shape around the peak. I would also compare amps without the
> | splitter).
> I cannot remove the splitter because without it we have no FADC trigger.
> We need to split one of the signals to discriminate it.   I agree there
> are details at the 10% level that relate to where the peak falls in the
> FADC clock.  But the fall time is slow enough that this cannot be more than
> exp(-2ns / 16ns) ~ 12%.  The FADC / scope discrepancy is much greater than
> that.  See Fernando's email for the numbers.

I would split the laser diod pulser and trigger from it (fadc could also
slightly override disc threshold as it DC coupled)

Cheers,
        Alex