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</style><article id="node-472361" class="node node-logentry article ia-n clearfix" role="article"><header class="node-header"><h1 class="node-title">
<a href="https://logbooks.jlab.org/entry/3399533" rel="bookmark">arc dipoles calibrations</a>
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<p class="author-datetime">
Lognumber <a href="https://logbooks.jlab.org/entry/3399533" class="lognumber" data-lognumber="3399533">3399533</a>. Submitted by <a href="https://logbooks.jlab.org/user/benesch">benesch</a> on <time datetime="2016-04-16T07:29:52-0400" pubdate="pubdate">Sat, 04/16/2016 - 07:29</time>. </p>
<p class="last-update">
Last updated on <time datetime="2016-04-16T07:30:32-0400" pubdate="pubdate">Sat, 04/16/2016 - 07:30</time></p>
<table class="field-vitals"><tr><th>Logbooks: </th><td><a href="https://logbooks.jlab.org/book/btlog">BTLOG</a></td></tr><tr><th>Entry Makers: </th><td>benesch</td></tr></table></div>
<div class="logentry node-content">
<p>Joe Grames reminded me yesterday that Yves Roblin and Doug Higinbotham had determined that the energy gain per linac on first pass was 1092.5 MeV/c from energy measurement and spin precession. The injector momentum is low by 2.5 MeV/c per BEM, 2%. It should be checked in the 0L06 spectrometer at some point. </p>
<p>If the injector momentum reads 123 MeV/c at 0L06, either the spectrometer dipole or MBL calibration is wrong. </p>
<p>In either event, since the energy in hall A was ~5 MeV high, arcs 1 and/or 2 are in error since they appear to be on design. </p>
<p>Assume the energy exiting the injector is 123 MeV/c and that the two linacs are at 1092.5 MeV/c as spin precession to arcs 4 and 5 suggest per Joe. </p>
<p>Energies for arcs 1-6, where synchrotron radiation is not a big loss, would be<br />
arc 1 1215.5 (1213)<br />
arc 2 2308 (2303)<br />
arc 3 3400.5 (3399)<br />
arc 4 4493 (4499)<br />
arc 5 5585.5 (5591)<br />
arc 6 6678 (6664)</p>
<p>Compare these values to the BEM momentum numbers in figure 1, in parentheses above. There are five discrepancies at the 0.001 - 0.002 level. Polarimetry measurements in hall A in all five passes would provide information for correction of the arc dipole field maps so Ops can more accurately establish the beam energy in the future. </p>
<p>--------------------<br />
Figures 2 and 3: I wondered why the hall A BEM indicator was red, so I opened the BPM screen. Most of the BPMs were red. Most of the BPMs should not be in the calculation at all: I'd include at most 1C07 to 1C17, two BPMs each at entry and exit and those in the arc proper. In figure 3 I show BEM with only the five green BPMs included. Figure 4 is the Hall A spike screen. 1C20 and the Compton BPMs show no wire sums, but all the BPMs before 1C20 and after Compton do. No beam in Compton. Figure 5 shows that 1C20 does respond.</p>
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<div class="image-wrapper"><img class="image-style-plentybig" src="cid:e25924810a7b3f7bf8849678be8fc5ab@logbooks.jlab.org" width="570" height="506" title="Fig. 1 [04/16/2016 06:55:07]" /></div> <div class="image-wrapper"><img class="image-style-plentybig" src="cid:62712f5e6cf10a645058d22aabbe236b@logbooks.jlab.org" width="298" height="863" title="Fig. 2 [04/16/2016 07:02:12]" /></div> <div class="image-wrapper"><img class="image-style-plentybig" src="cid:8f617f08308c0af8ee061086226f4934@logbooks.jlab.org" width="579" height="543" title="Fig. 3 [04/16/2016 07:02:28]" /></div> <div class="image-wrapper"><img class="image-style-plentybig" src="cid:49c8e1007c3d01be9e4a0eee6f0e8223@logbooks.jlab.org" width="853" height="863" title="Fig. 4 [04/16/2016 07:23:30]" /></div> <div class="image-wrapper"><img class="image-style-plentybig" src="cid:086a57cbd3ea1eab4d5bcbd406f4dba8@logbooks.jlab.org" width="849" height="884" title="Fig. 5 [04/16/2016 07:29:12]" /></div> </div>
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