Hi Diana,<br><br>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:<br><br><a href="http://www.jlab.org/~adaq/halog/html/0902_archive/090222135910.html">http://www.jlab.org/~adaq/halog/html/0902_archive/090222135910.html</a><br>
<br>-Matt<br><br><div class="gmail_quote">On Mon, Feb 7, 2011 at 9:41 PM, Brad Sawatzky <<a href="mailto:brads@jlab.org">brads@jlab.org</a>> wrote:<br><blockquote class="gmail_quote">
The online discriminator threshold was 70mV as you found (it's also at<br>
the end of every start-of-run halog entry). That is roughly 1.5 p.e.'s<br>
This is is the signal that helped form our primary trigger.<br>
<br>
The optimal offline threshold is the one that Matt's study identified as<br>
giving the optimal signal:noise ratio.<br>
<br>
We would have run with a 3 p.e. threshold in the online trigger if the<br>
mirrors had been good enough to give us the predicted number of photons<br>
per electron track. This would have made a huge difference in the<br>
performance of the Cerenkov on the beamline-side. Unfortunately the<br>
mirrors turned out to suck, and we had to run with a lower threshold.<br>
<br>
-- Brad<br>
<div class="im"><br>
On Mon, 07 Feb 2011, Diana Parno wrote:<br>
<br>
> I'm wondering what the hardware threshold on the BB Cerenkov was<br>
> during the experiment, in terms of number of photoelectrons. I found a<br>
> HALOG entry placing the threshold at -0.070 V:<br>
><br>
> <a href="http://www.jlab.org/%7Eadaq/halog/html/0902_archive/090210201819.html">http://www.jlab.org/~adaq/halog/html/0902_archive/090210201819.html</a><br>
><br>
> Brad's Cerenkov tech note talks about gain-matching the PMTs to place<br>
> the one-p.e. peak at about 50 mV, which would put the threshold at<br>
> about 1.4 p.e. On the other hand, page 4 talks about a 3-p.e.<br>
> threshold, and I am not sure from context whether that's supposed to<br>
> be a hardware (online trigger) threshold or a software (offline cut)<br>
> threshold. If the threshold is 1.4 p.e., do we have a rough idea as to<br>
> the online pion rejection factor? (If it's 3 p.e., then Matt's study<br>
> from last month would give that factor, if I'm not mistaken.)<br>
><br>
> Best,<br>
> Diana<br>
><br>
</div><font color="#888888">--<br>
Brad Sawatzky, PhD <<a href="mailto:brads@jlab.org">brads@jlab.org</a>> -<>- Jefferson Lab / Hall C / C111<br>
Ph: 757-269-5947 -<>- Fax: 757-269-5235 -<>- Pager: <a href="mailto:brads-page@jlab.org">brads-page@jlab.org</a><br>
The most exciting phrase to hear in science, the one that heralds new<br>
discoveries, is not "Eureka!" but "That's funny..." -- Isaac Asimov<br>
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</div></div></blockquote></div><br><br clear="all"><br>-- <br>Matthew Posik<br>Email: <a href="mailto:posik@temple.edu">posik@temple.edu</a><br>Temple University Physics Dept.<br>Office: BA-319<br>Office #: 215-204-1331 <br>
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