<html>
<head>
<meta content="text/html; charset=windows-1252"
http-equiv="Content-Type">
</head>
<body text="#000000" bgcolor="#FFFFFF">
<div class="moz-cite-prefix">Hi Nathan,<br>
this is a very interesting study. I'd like to add a comment to the
discussion (something we already mentioned some time ago at one of
the Ecal meetings)<br>
<br>
- In FADC mode 7, for every event and for every channell over
threshold, we record 4 numbers: <br>
* Energy (in FADC counts, i.e the sum of the samples around the
signal peak)<br>
* Time<br>
* Pedestal (average of the first 4 samples, in FADC counts)<br>
* Signal amplitude (in FADC counts, i.e. the max signal height)<br>
<br>
We can think about 2 ways of subtracting the pedestal using these
data<br>
<br>
1) Event by event, as energy - pedestal *
fadc_integration_window_width<br>
2) On average, computing the average pedestal for a given channel
over the run, and then subtracting it as before<br>
<br>
If we expect the pedestal to be roughly constant during a run (if
the beam current is constant), then I expect the second solution
to be better than the first one.<br>
With the first solution, event by event the pedestal noise affects
the energy resolution.<br>
<br>
<br>
Andrea<br>
<br>
On 01/10/2015 10:48 PM, Nathan Baltzell wrote:<br>
</div>
<blockquote cite="mid:2BA0F196-3319-439C-9C67-CB2D21A5EBFE@jlab.org"
type="cite">
<pre wrap="">Hi Everyone,
Here is a recent look at some pedestal studies. It appears they have an effect from pileup.
It’s not significant for many channels, but for high rate channels near the beam I think we
are going to want to correct it. It would be interesting to see if Luca’s gain calibration sees
any current-dependence coming from incorrect pedestals.
-Nathan
</pre>
<br>
<fieldset class="mimeAttachmentHeader"></fieldset>
<br>
<pre wrap="">_______________________________________________
Hps-ecal mailing list
<a class="moz-txt-link-abbreviated" href="mailto:Hps-ecal@jlab.org">Hps-ecal@jlab.org</a>
<a class="moz-txt-link-freetext" href="https://mailman.jlab.org/mailman/listinfo/hps-ecal">https://mailman.jlab.org/mailman/listinfo/hps-ecal</a>
</pre>
</blockquote>
<br>
</body>
</html>