<html><head><style type='text/css'>p { margin: 0; }</style></head><body><div style='font-family: arial,helvetica,sans-serif; font-size: 12pt; color: #000000'>Hi Dan,<br><br>We generally cover 30CM BR and downstream of the poles. It looks like we cover what you ask for. We can do hand measurements at the focal plane.<br><br><div><span name="x"></span>Tim <span word="Whitlatch" id="DWT3816" class="ZM-SPELLCHECK-MISSPELLED">Whitlatch</span><br>Hall D Engineer<br>Jefferson Lab<br>12050 Jefferson Ave <span word="ste" id="DWT3817" class="ZM-SPELLCHECK-MISSPELLED">ste</span> 402<br>Newport News, Va 23606<br>757-269-5087<span name="x"></span><br></div><br><hr id="zwchr"><div style="color:#000;font-weight:normal;font-style:normal;text-decoration:none;font-family:Helvetica,Arial,sans-serif;font-size:12pt;"><b>From: </b>"Daniel Sober" <sober@<span word="cua" id="DWT3818" class="ZM-SPELLCHECK-MISSPELLED">cua</span>.<span word="edu" id="DWT3819" class="ZM-SPELLCHECK-MISSPELLED">edu</span>><br><b>To: </b>"Hall D beam working group" <halld-tagger@<span word="jlab" id="DWT3820" class="ZM-SPELLCHECK-MISSPELLED">jlab</span>.org>, "Timothy <span word="Whitlatch" id="DWT3821" class="ZM-SPELLCHECK-MISSPELLED">Whitlatch</span>" <whitey@<span word="jlab" id="DWT3822" class="ZM-SPELLCHECK-MISSPELLED">jlab</span>.org><br><b>Sent: </b>Monday, October 7, 2013 5:03:10 PM<br><b>Subject: </b>Field mapping diagram and fringe field<br><br>
Dear Tim <span word="et" id="DWT3823" class="ZM-SPELLCHECK-MISSPELLED">et</span> <span word="al" id="DWT3824" class="ZM-SPELLCHECK-MISSPELLED">al</span>.,<br>
Here's an updated version of the map request in the form of a
diagram in mapper coordinates. I think it reflects most of what you
reported earlier.<br>
The main thing I would like to add is to assure that we make some
provision for measuring the <b>fringe field at the exit flange</b>,
which is about 6 cm from the nominal focal plane. This field will
be of order 10 <span word="gauss" id="DWT3825" class="ZM-SPELLCHECK-MISSPELLED">gauss</span>, and only a crude hand measurement is needed,
but it may be important in adding another significant figure to the
energy calibration. We also need to know whether the magnetic
shielding planned for the fixed-array <span word="PMTs" id="DWT3826" class="ZM-SPELLCHECK-MISSPELLED">PMTs</span> in this region is
adequate.<br>
If you have not made other arrangements for measuring this fringe
field, I would propose marking off distances along the exit flange
and making a measurement with a hand-held <span word="gaussmeter" id="DWT3827" class="ZM-SPELLCHECK-MISSPELLED">gaussmeter</span> at intervals of
about 50 cm. The origin of coordinates could be referred to the
magnet yoke.<br>
Dan<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" target="_blank">sober@<span word="cua" id="DWT3828" class="ZM-SPELLCHECK-MISSPELLED">cua</span>.<span word="edu" id="DWT3829" class="ZM-SPELLCHECK-MISSPELLED">edu</span></a></i></font><br>
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