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<div class="moz-cite-prefix">Dan,<br>
<br>
Some things to keep in mind:<br>
<ol>
<li>remember the quadrupole is vertically focusing, and can be
tuned to improve things near the endpoint when the physics
requires endpoint energies<br>
</li>
<li>the gap is 3cm<br>
</li>
<li>there is significant scraping at 11.7 GeV under GlueX
running conditions<br>
</li>
<li>we chose 11.7 GeV because things get impossible above that,
even with the quad<br>
</li>
</ol>
<p>-Richard J.<br>
</p>
<ol>
<li>On 6/27/2012 4:49 PM, Daniel Sober wrote:</li>
</ol>
</div>
<blockquote cite="mid:4FEB71C8.2030905@cua.edu" type="cite">
I have put the current tagger magnet into my old codes and come up
with at least one interesting result that needs investigating:
Using a realistic bremsstrahlung calculation integrated over
photon angles (Maximon and Lepretre, 1985) for an amorphous gold
radiator,<br>
the fraction of the bremsstrahlung electron cone clearing the 2 cm
magnet gap gets bad rather quickly as k/E0 > 0.95, with only
81% transmitted at k/E0 = 0.98. See the attached files, one for
the full range and the other in fine steps near the endpoint. Some
of the numbers in the header (especially "FULL-ENERGY ANGLE") may
not make sense to you, but they generate what we need. The second
column (Gap frac.) gives the fraction of electrons clearing the 2
cm gap, neglecting the Rogowski chamfer which will make things a
little better -- I will need a detailed drawing of the pole shape
to account for this effect. The subsequent columns give the
fraction passing through a given detector full width. (The
"negative" fractions just flag the cases where the magnet gap is
the limiting aperture.) <br>
<br>
I am not set up to calculate coherent bremsstrahlung or the effect
of photon collimation, but with some work I could plug in the
appropriate electron angular distributions if I had them.<br>
<br>
Dan<br>
<br>
<div>-- <br>
<i>Daniel Sober<br>
Professor<br>
Physics Department<br>
The Catholic University of America<br>
Washington, DC 20064<br>
Phone: (202) 319-5856, -5315<br>
E-mail: <a href="mailto:sober@cua.edu">sober@cua.edu</a></i>
<br>
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</blockquote>
<br>
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