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<p class="MsoNormal"><span style="font-size:12.0pt;mso-contextual-alternates:yes">Thank you very much Brian for the detailed explanation.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:12.0pt;mso-contextual-alternates:yes">So far so good. Taking data without any issue related to the solenoid.
<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:12.0pt;mso-contextual-alternates:yes"><o:p> </o:p></span></p>
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<p class="MsoNormal"><span style="font-size:11.0pt;color:black">-------------------------------------------<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;color:black"># Patrizia Rossi<br>
# Jefferson Lab <br>
# 12000 Jefferson Avenue<br>
# Suite 5<br>
# Newport News VA 23606 (USA)<br>
# e-mail: </span><span style="font-size:11.0pt"><a href="mailto:rossi@jlab.org"><span style="color:#0563C1">rossi@jlab.org</span></a><span style="color:black"><br>
# phone: +1 (757) 269 7740<br>
# fax: + 1 (757) 269 5800</span><o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-size:12.0pt;mso-contextual-alternates:yes"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:12.0pt;mso-contextual-alternates:yes"><o:p> </o:p></span></p>
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<p class="MsoNormal" style="margin-bottom:12.0pt"><b><span style="font-size:12.0pt;color:black">From:
</span></b><span style="font-size:12.0pt;color:black">Brian Eng <beng@jlab.org><br>
<b>Date: </b>Saturday, November 5, 2022 at 3:53 PM<br>
<b>To: </b>dsg-hallb magnets <dsg-hallb_magnets@jlab.org><br>
<b>Cc: </b>Patrizia Rossi <rossi@jlab.org><br>
<b>Subject: </b>Solenoid QDs<o:p></o:p></span></p>
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<p class="MsoNormal" style="background:white"><span style="font-size:12.0pt;color:black">First a quick bit of background ... There are 3 levels of quench detection (QDs) for the solenoid:<o:p></o:p></span></p>
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<p class="MsoNormal" style="background:white"><span style="font-size:12.0pt;color:black"><o:p> </o:p></span></p>
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<p class="MsoNormal" style="background:white"><span style="font-size:12.0pt;color:black">1. slow dump aka controlled ramp (current set to 0 A) done by the PLC<o:p></o:p></span></p>
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<p class="MsoNormal" style="background:white"><span style="font-size:12.0pt;color:black">2. fast dump done by the PLC<o:p></o:p></span></p>
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<p class="MsoNormal" style="background:white"><span style="font-size:12.0pt;color:black">3. fast dump done by the hardware QD boards<o:p></o:p></span></p>
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<p class="MsoNormal" style="background:white"><span style="font-size:12.0pt;color:black"><o:p> </o:p></span></p>
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<p class="MsoNormal" style="background:white"><span style="font-size:12.0pt;color:black">The thresholds on each of these is set such that 1 < 2 < 3. For the purposes of the recent events we'll ignore levels 2 and 3.<o:p></o:p></span></p>
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<p class="MsoNormal" style="background:white"><span style="font-size:12.0pt;color:black"><o:p> </o:p></span></p>
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<p class="MsoNormal" style="background:white"><span style="font-size:12.0pt;color:black">There are 21 voltage taps on the solenoid are these are combined in various ways to make up 10 comparators that are what the thresholds are evaluated against, all use the
absolute value. See images VT.png for the physical locations and COMP.png for the math involved.<o:p></o:p></span></p>
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<p class="MsoNormal" style="background:white"><span style="font-size:12.0pt;color:black"><o:p> </o:p></span></p>
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<p class="MsoNormal" style="background:white"><span style="font-size:12.0pt;color:black">These voltage taps are sampled at 10kHz by the cRIO and every 200 ms the average of 2000 samples is sent to the PLC. These averages are what the PLC uses to combine into
the actual values used to generate a slow dump. There is also an additional 1.25 second delay in the PLC before a trip is generated, which means the value would need to be bad for around 6 consecutive readings for the PLC to generate a fault.<o:p></o:p></span></p>
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<p class="MsoNormal" style="background:white"><span style="font-size:12.0pt;color:black"><o:p> </o:p></span></p>
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<p class="MsoNormal" style="background:white"><span style="font-size:12.0pt;color:black">I looked at the fast daq data from the cRIO (i.e. the raw 10 kHz data) at a three different times: full negative current, full positive current, and zero current, see attached
Excel file mainly the Statistics sheet. Do note that these numbers were done by eye and should all be thought of as approximations.<o:p></o:p></span></p>
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<p class="MsoNormal" style="background:white"><span style="font-size:12.0pt;color:black"><o:p> </o:p></span></p>
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<p class="MsoNormal" style="background:white"><span style="font-size:12.0pt;color:black">What Probir and I had thought was a potential issue (VT17 being significantly noisier than VT3) probably isn't really one as that is always noisy in either polarity and
the PLC is only using the mean. Really the only thing that seems so stand out is that COMP3 is extremely close to the previous trip point of 0.08 V but that really depends on the size of the window that the data is examined in.<o:p></o:p></span></p>
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<p class="MsoNormal" style="background:white"><span style="font-size:12.0pt;color:black"><o:p> </o:p></span></p>
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<p class="MsoNormal" style="background:white"><span style="font-size:12.0pt;color:black">Hopefully the increase in threshold earlier today will help. <span class="contentpasted0"><span style="background:white">Maybe the lead/splice QD thresholds can be raised
even more?</span></span><o:p></o:p></span></p>
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<p class="MsoNormal" style="background:white"><span style="font-size:12.0pt;color:black"><o:p> </o:p></span></p>
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<p class="MsoNormal" style="background:white"><span style="font-size:12.0pt;color:black">There is also a change so that we can monitor the status of the PLC comparators in EPICS that will be deployed the next time the magnets are ramped down to zero amps.<o:p></o:p></span></p>
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<p class="MsoNormal" style="background:white"><span style="font-size:12.0pt;color:black"><o:p> </o:p></span></p>
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<p class="MsoNormal" style="background:white"><span style="font-size:12.0pt;color:black">If anyone has any questions or comments let me know.<o:p></o:p></span></p>
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