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Dear Folks,<br>
<br>
One possibility suggested by Dave Kashy (with modifications from Stepan
and Eugene) is to use the primary electron beam to calibrate the
tagger. <br>
<ol>
<li>Put a 300 MeV pulsed low-current electron through the tagger
magnet <br>
</li>
<li>Sweep the magnet field slowly. <br>
</li>
<li>Read out the tagger detector scalers and the tagger magnet
current in epics. <br>
</li>
<li>Correlate the magnet current with the location of each of the
tagger detectors.</li>
</ol>
After the TPE run, when we have replaced the detectors, repeat the
procedure to determine the precise locations of the detectors. <br>
<br>
According to Arne, it would take about 12 hours to configure the
machine in this way. It would take an hour or two to do the
measurement, so the total time required would be less than one day of
exclusive beam (ie: no other expt can run during this time). <br>
<br>
If Qweak is willing to let us do this, we can do this before the summer
shutdown. Alternatively, if Primex runs before TPE, we could do this
at the end of the Primex run. It would be better do this before the
summer shutdown to allow us the flexibility of removing low energy
tagger counters during the summer shutdown (assuming that Primex won't
use them).<br>
<br>
Note that this assumes that TPE will run this fall.<br>
<pre cols="72" class="moz-signature">--
Sincerely,
Larry
-----------------------------------------------------------
Lawrence Weinstein
University Professor
Physics Department
Old Dominion University
Norfolk, VA 23529
757 683 5803
757 683 3038 (fax)
<a href="mailto:weinstein@odu.edu">weinstein@odu.edu</a>
<a href="http://www.lions.odu.edu/~lweinste/">http://www.lions.odu.edu/~lweinste/</a></pre>
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