<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>
<meta content="text/html; charset=ISO-8859-1"
http-equiv="Content-Type">
</head>
<body bgcolor="#ffffff" text="#000000">
I forgot to mention:<br>
Always the first and the last channel of a preamp have some tail.<br>
This is an edge effect when the edge strip is not the center of the<br>
cluster I guess but rather the upper and lower edge respectively<br>
and given only one strip hit for this event.<br>
<br>
cheers,<br>
Beni<br>
<br>
<br>
<blockquote cite="mid:4DD29AD6.8010901@jlab.org" type="cite">Hi
Gerard,
<br>
thanks for the idea. I took only the fastest trip for each preamp
card.
<br>
had here the result. This cleans up the spectra dramatically. Also
you
<br>
can see that for a given card the timing seems to drift for groups
of
<br>
strips. In particular strip 1 ot 24 you see a distinctive wiggle.
<br>
<br>
cheers,
<br>
Beni
<br>
<br>
<blockquote type="cite">Hi Beni,
<br>
I'm not sure what to make of that tail either. One question
that might be
<br>
related: are you putting a point on the histogram for every
strip? What would it
<br>
look like if you just used the earliest strip hit? Certainly the
side strips
<br>
which see smaller signal will not cross the timing threshold as
soon as the
<br>
central strip(s) do. That effect must produce a tail to the left
in this plot,
<br>
but whether it would be such an extreme tail, I don't have a
clue.
<br>
Have you had an opportunity to begin to optimize the LE
threshold? (I'm still
<br>
guessing this would mainly be done with a goal of overall drift
coordinate
<br>
resolution, so maybe that has to wait a bit. But on the other
hand also would
<br>
worry that all results are threshold dependent and is it set
roughly where we
<br>
will want it?)
<br>
Sincerely,
<br>
<br>
Gerard
<br>
<br>
On 5/17/2011 8:20 AM, Beni Zihlmann wrote:
<br>
<blockquote type="cite">Hi All,
<br>
attached are 3 plots. The first is a 2d plot for FDC wire 11
on cosmic
<br>
data. The vertical axis is the strip number and the horizontal
axis
<br>
is the time difference between the strip and wire 11. The
times are
<br>
determined using Gerard's algorithm with interpolation on the
FDC
<br>
data for both the wire and the strip. Note that the time
difference
<br>
is calculated as "t_wire - t_strip" so the long tail to the
negative times
<br>
is due to the strip while we have a rather sharp edge on the
right side.
<br>
this can be seen more clearly when looking at the projection
of the 2d
<br>
plot to the horizontal axis. This is shown in the next to
plots individually
<br>
for the channel 0-23 and 24-47 which represents the two preamp
cards
<br>
for the top and bottom cathode planes. I try to extract a
width by fitting
<br>
mostly only the upper edge. As you can see the width is
between 1 and
<br>
1.5 ns. So the individual resolution may be about sqrt(2)
better. You can
<br>
also see that the timing resolution depends on the average
signal amplitude
<br>
which is smaller for the second preamp (channel 24-47). I do
not know what
<br>
causes the shift in time between the two preamp card. This
shift is certainly
<br>
much larger than any cable length miss match etc. But Lubomir
observed
<br>
this behavior already earlier.
<br>
What causes the long tail to negative time difference is not
completely clear
<br>
to me. One reason might be that there are considerable gain
variations between
<br>
strip channels and I plot all hits not just the one with the
largest amplitude
<br>
in a hit.
<br>
Let me know if you have additional ideas what else one could
tests.
<br>
<br>
cheers,
<br>
Beni
<br>
</blockquote>
_______________________________________________
<br>
Halld-tracking-hw mailing list
<br>
<a class="moz-txt-link-abbreviated" href="mailto:Halld-tracking-hw@jlab.org">Halld-tracking-hw@jlab.org</a>
<br>
<a class="moz-txt-link-freetext" href="https://mailman.jlab.org/mailman/listinfo/halld-tracking-hw">https://mailman.jlab.org/mailman/listinfo/halld-tracking-hw</a>
<br>
</blockquote>
<br>
<pre wrap="">
<fieldset class="mimeAttachmentHeader"></fieldset>
_______________________________________________
Halld-tracking-hw mailing list
<a class="moz-txt-link-abbreviated" href="mailto:Halld-tracking-hw@jlab.org">Halld-tracking-hw@jlab.org</a>
<a class="moz-txt-link-freetext" href="https://mailman.jlab.org/mailman/listinfo/halld-tracking-hw">https://mailman.jlab.org/mailman/listinfo/halld-tracking-hw</a></pre>
</blockquote>
<br>
</body>
</html>