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Dear colleagues,<br>
<br>
Since Kei wrote up a fairly complete description of his work, I
thought I should pass it along to everyone for reference.<br>
<br>
Cheers, Elton.<br>
<br>
-------- Original Message --------
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<th align="RIGHT" nowrap="nowrap" valign="BASELINE">Subject: </th>
<td>Re: Beam Test Meeting Minutes + new time</td>
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<th align="RIGHT" nowrap="nowrap" valign="BASELINE">Date: </th>
<td>Tue, 28 Feb 2012 11:59:26 -0500</td>
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<th align="RIGHT" nowrap="nowrap" valign="BASELINE">From: </th>
<td>Kei Moriya <a class="moz-txt-link-rfc2396E" href="mailto:kmoriya@indiana.edu"><kmoriya@indiana.edu></a></td>
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<th align="RIGHT" nowrap="nowrap" valign="BASELINE">To: </th>
<td><a class="moz-txt-link-abbreviated" href="mailto:leckey@jlab.org">leckey@jlab.org</a></td>
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<th align="RIGHT" nowrap="nowrap" valign="BASELINE">CC: </th>
<td><a class="moz-txt-link-abbreviated" href="mailto:davidl@jlab.org">davidl@jlab.org</a>, <a class="moz-txt-link-abbreviated" href="mailto:somov@jlab.org">somov@jlab.org</a>, <a class="moz-txt-link-abbreviated" href="mailto:hovanes@jlab.org">hovanes@jlab.org</a>,
<a class="moz-txt-link-abbreviated" href="mailto:elton@jlab.org">elton@jlab.org</a>, <a class="moz-txt-link-abbreviated" href="mailto:mashephe@indiana.edu">mashephe@indiana.edu</a>, Zisis Papandreou
<a class="moz-txt-link-rfc2396E" href="mailto:zisis@uregina.ca"><zisis@uregina.ca></a></td>
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<br>
<pre>Dear beam testers (I've added Zisis too for this email),
A quick explanation of what I presented at today's calorimetry
meeting, since my audio was not functioning.
The figures I refer to are at
<a class="moz-txt-link-freetext" href="http://dustbunny.physics.indiana.edu/~kmoriya/note.pdf">http://dustbunny.physics.indiana.edu/~kmoriya/note.pdf</a>
I was working on this for GEANT simulations, but am sending this
around since it may be relevant when we are trying to match
up with the CLAS scintillators.
The top figure shows a horizontal array of cyan dots,
which is where the detector will be with perfect alignment.
The blue dots you see at the top, which are labeled E-counters,
are the CLAS E-counters (4mm thick). Similarly, the green dots
are the T-counters, which are 2 cm thick, and are in a plane
that is 20 cm parallel and downstream of the E-counters.
The magenta dots above the E-counters is the exit window,
where the electrons come out of the vacuum.
What I have done is calculate the distance between
- the exit window and our detector front plane (total flight path)
- the exit window and E-counter
- the E-counters and T-counters
For example, if you look at the red detector shown, it has a
cyan dot in the detector front plane, and a red electron trajectory
going through it. If you follow this trajectory upstream, you will
see where it hits the corresponding T-counter (green), then
E-counter (blue), then the exit window (magenta). So for each
energy fraction, we can calculate the distances between each
component that the electron goes through.
This is shown in the bottom plot, where
- green = total distance traveled between exit window and detector
- blue = exit window and E-counter
- red = E-counter and T-counter
for each energy fraction.
All of these distances were calculated assuming the alcove floor
height, and since the alcove exists only to an energy fraction
of ~0.20, please ignore the points beyond ~0.20.
The main point is that the electrons will travel ~4 m or so in
total through the air, and will therefore travel ~3 m after going
through first a 4 mm scintillator, then a 2 cm one.
The second page in the note shows the same figures, but with
the detector placed on the floor area (see the cyan dots showing
the detector front face). Again, since we can only use energy
fractions of > 0.23, ignore points to the left of 0.23.
The main point here will be that at the higher energy points,
there will be a flight path of ~1 m between the E-counters and T-counters
(although the planes are only 20 cm apart), and at the position
where we have just cleared the alcove ledge (fraction ~0.23),
the electrons will travel ~6-7 m after going through the
CLAS scintillators.
I do not think this explains why we have no hits at all
in our remotes in coincidence with the CLAS taggers, but
these numbers may be of use in future rough calculations.
For GEANT simulations, I will put these CLAS components
in with the correct distances, and will see how the energy
spread and resolution changes when these are put in.
If anybody needs any numbers, I can supply them with tables
or functions that will do the calculation.
For the FCAL GEANT simulations, the undergrads I have been
working with have put in the front end material we have for
our detector.
I will give an update on the GEANT simulations soon.
Kei
(2/28/12 10:41 AM), <a class="moz-txt-link-abbreviated" href="mailto:leckey@jlab.org">leckey@jlab.org</a> wrote:
> Hi,
>
> I have posted the brief minutes from the beam test meeting on the wiki.
>
> As a reminder, this meeting will become a permanent beam test meeting, not
> just a FCAL beam test meeting, and it will meet at 1030 on Mondays.
>
> John
>
</pre>
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