[d2n-analysis-talk] BB Cerenkov hardware threshold

[Matthew R. Posik]

Hi Diana,

Just FYI, you can also see the ADC threshold by plotting the TDCs vs the
ADCs. Yi gives a pretty good description of what these plots show in the
last paragraph here:

http://www.jlab.org/~adaq/halog/html/0902_archive/090222135910.html

-Matt

On Mon, Feb 7, 2011 at 9:41 PM, Brad Sawatzky <brads at jlab.org> wrote:

> The online discriminator threshold was 70mV as you found (it's also at
> the end of every start-of-run halog entry).  That is roughly 1.5 p.e.'s
> This is is the signal that helped form our primary trigger.
>
> The optimal offline threshold is the one that Matt's study identified as
> giving the optimal signal:noise ratio.
>
> We would have run with a 3 p.e. threshold in the online trigger if the
> mirrors had been good enough to give us the predicted number of photons
> per electron track.  This would have made a huge difference in the
> performance of the Cerenkov on the beamline-side.  Unfortunately the
> mirrors turned out to suck, and we had to run with a lower threshold.
>
> -- Brad
>
> On Mon, 07 Feb 2011, Diana Parno wrote:
>
> > I'm wondering what the hardware threshold on the BB Cerenkov was
> > during the experiment, in terms of number of photoelectrons. I found a
> > HALOG entry placing the threshold at -0.070 V:
> >
> > http://www.jlab.org/~adaq/halog/html/0902_archive/090210201819.html
> >
> > Brad's Cerenkov tech note talks about gain-matching the PMTs to place
> > the one-p.e. peak at about 50 mV, which would put the threshold at
> > about 1.4 p.e. On the other hand, page 4 talks about a 3-p.e.
> > threshold, and I am not sure from context whether that's supposed to
> > be a hardware (online trigger) threshold or a software (offline cut)
> > threshold. If the threshold is 1.4 p.e., do we have a rough idea as to
> > the online pion rejection factor? (If it's 3 p.e., then Matt's study
> > from last month would give that factor, if I'm not mistaken.)
> >
> > Best,
> > Diana
> >
> --
> Brad Sawatzky, PhD <brads at jlab.org>  -<>-  Jefferson Lab / Hall C / C111
> Ph: 757-269-5947  -<>-  Fax: 757-269-5235  -<>- Pager: brads-page at jlab.org
> The most exciting phrase to hear in science, the one that heralds new
>  discoveries, is not "Eureka!" but "That's funny..."   -- Isaac Asimov
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-- 
Matthew Posik
Email: posik at temple.edu
Temple University Physics Dept.
Office: BA-319
Office #:  215-204-1331
WebSites:
Temple:
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d2n:
http://hallaweb.jlab.org/experiment/E06-014/
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