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Dear Folks,<br>
<br>
The downstream collimator is a cylinder 40 mm ID, 98 mm OD and about 6"
long. It is currently lead and we would like it to be tungsten (based
on Cristian's simulation results).<br>
<br>
1) The downstream collimator will be tungsten ID 40 mm, OD 76.2 mm
with a lead jacket ID 76.2 mm, OD 98 mm. It will take 4-6 weeks to get
a bigger piece of tungsten so that the entire piece is made of
tungsten. We do not have that time.<br>
2) Dave K suggests that we taper or step the ID of the tungsten to
reduce the effects of a possible misalignment and to let the tungsten
also be its own clean-up collimator. Do we want the collimator to be
ID 40 mm for the first half (3") and then ID 42 mm for the 2nd half? <br>
a) Do we want a step in the collimator?<br>
b) If so, where do we want the step (how far downstream)?<br>
c) How big do we want the ID change to be?<br>
<br>
I will discuss this with Dave Monday (and I will not be available
tomorrow).<br>
<br>
- Larry<br>
<br>
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<th valign="BASELINE" nowrap="nowrap" align="RIGHT">Subject: </th>
<td>collimator at target</td>
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<th valign="BASELINE" nowrap="nowrap" align="RIGHT">Date: </th>
<td>Thu, 14 Oct 2010 16:56:55 -0400</td>
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<th valign="BASELINE" nowrap="nowrap" align="RIGHT">From: </th>
<td>David Kashy <a href="mailto:kashy@jlab.org"><kashy@jlab.org></a></td>
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<th valign="BASELINE" nowrap="nowrap" align="RIGHT">To: </th>
<td>Larry Weinstein <a href="mailto:weinstei@jlab.org"><weinstei@jlab.org></a></td>
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<br>
<br>
<pre>Hi Larry,
The shop tells me to get tungsten of 4" OD will be 4-5 weeks just for
the material, I called a place my self and they said 5-6 weeks. I don't
think we should risk the delay since there is a piece at the shop that
is 3" od and just over 6" long.
I did have an idea that you might want to consider.
We could make a taper or step in the ID so that slight miss alignment of
the collimator has less effect that would be something like making the
first 2, 3 or 4" with 40 mm id and the final 4 , 3 or 2 inches is 42mm
or 44mm
Let me know
Dave
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