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Dear Alex and Richard,<br>
Sorry for the error. I should get a full set of magnet dimensions
so that I can do things correctly the first time.<br>
Attached is the calculation for the 3 cm gap. If there is any
dedicated amorphous-radiator running with interest in the endpoint
region, one could improve things by putting the radiator closer: a
distance of 1.5 m (instead of 3.19 m) would increase the gap
acceptance from .858 to .948 at k/E0 = 0.980 and from .895 to 0.962
at k/E0=0.975 (11.7 GeV) without substantially changing the energy
resolution all the way down to the microscope.<br>
My primary goal in resuscitating these codes is to work out the
counter placement at the high energies. Should I consider pushing
to .980 (11.76 GeV)?<br>
Dan<br>
<br>
<div class="moz-cite-prefix">On 6/27/2012 9:22 PM, Richard Jones
wrote:<br>
</div>
<blockquote cite="mid:4FEBB1C0.2050107@uconn.edu" type="cite">
<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>
</div>
</blockquote>
<br>
<br>
</blockquote>
<br>
<div class="moz-signature">-- <br>
<font color="#ff0000"><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></font><br>
</div>
<br>
<br>
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