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<div id="divRplyFwdMsg" dir="ltr"><font style="font-size:11pt" face="Calibri, sans-serif" color="#000000"><b>From:</b> Sanghwa Park <sanghwa@jlab.org><br>
<b>Sent:</b> Friday, August 21, 2020 9:32 AM<br>
<b>To:</b> bteam@jlab.org <bteam@jlab.org><br>
<b>Cc:</b> HyeKyoung Park <hkpark@jlab.org>; Paschke, Kent Dieter (kdp2c) <paschke@virginia.edu>; Ciprian Gal <ciprian@jlab.org><br>
<b>Subject:</b> Hall A data from FFB and FF test</font>
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<div>Hello all,</div>
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<div>Thank you for the discussion this morning. Here is some information when we did the test with FFB system. </div>
<div>Please let me know if you need anything from us. We are happy to provide any information that would help.<br>
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<div>I put the timestamps of our runs which would be useful for you to look at the archive.</div>
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<div>We took two runs, </div>
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<div>run 7699:</div>
<div>Run start time: 2020-08-13 17:00:06 </div>
<div>Run end time: 2020-08-13 17:44:58</div>
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<div>"During" the run, we test (1) FF ON, FFB ON (2) FF ON, FFB pause. The plots below show the comparisons of BPM1Y. Note the vertical scale on the right plot.<br>
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<div>On the right plot, x-axis is the entry number of our data, so it's time proxy. Each entry is for one helicity window at 120Hz.</div>
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<div>Observation: With FF on, we see vertical jitter in our BPMs. The plots only show BPM1Y here but other BPMs saw it too.</div>
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<div><img alt="image.png" width="542" height="514" data-outlook-trace="F:1|T:1" src="cid:ii_ke496hhw1"><br>
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<div>run 7700:</div>
<div>Run start time: 2020-08-13 17:46:26</div>
<div>Run end time: 2020-08-13 18:02:36</div>
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<div>During this run, we test (1) FF OFF, FFB ON (2) FF OFF, FFB pause. BPM1Y comparisons plots are attached below. </div>
<div>Observation: whether we have FFB on or not, if FF is off we didn't see the large jitter anymore.</div>
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<div><img alt="image.png" width="541" height="542" data-outlook-trace="F:1|T:1" src="cid:ii_ke496qrq2"></div>
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<div>Also, we observed that Hall A Compton central rate (backscattered photon, not background rate) behaves better with FFB and FF OFF. See <a href="https://logbooks.jlab.org/entry/3826851" target="_blank">https://logbooks.jlab.org/entry/3826851</a></div>
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<div>The strip chat shows the compton central rate and FFB status. </div>
<div>Top graph is the Compton central rate. The bottom one is FFB status, =FFB ON, 0=FFB off. </div>
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<div>Sanghwa (Hall A RC)</div>
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<div dir="ltr"><span style="font-size:12.8px">Sanghwa Park</span>
<div style="font-size:12.8px">Stony Brook University</div>
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