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<p class="MsoNormal">I think we should do a quick HV scan of the new layer at low luminosity, say 1 uA LH2. The efficiency calculation is going to be more reliable there. Then we can quickly see where we stand and if we are well below the plateau.
<o:p></o:p></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">Sean Jeffas <sj9ry@virginia.edu><br>
<b>Date: </b>Thursday, November 18, 2021 at 4:47 PM<br>
<b>To: </b>Gnanvo, Kondo (kg6cq) <kg6cq@virginia.edu><br>
<b>Cc: </b>Holly Szumila-Vance <hszumila@jlab.org>, Andrew Puckett <puckett@jlab.org>, Liyanage, Nilanga K (nl8n) <nl8n@virginia.edu>, sbs_gems@jlab.org <sbs_gems@jlab.org><br>
<b>Subject: </b>Re: [Sbs_gems] [EXTERNAL] UV GEM HV Settings<o:p></o:p></span></p>
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<p class="MsoNormal">I suppose we need a clearer description for signs that the detector need a higher voltage setting. As Andrew has been working with the analysis software he has repeatedly maintained that the we should not go off of the GEM efficiencies
that the analysis quotes. So what should we look for to decide that the voltage is getting too low?<o:p></o:p></p>
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<p class="MsoNormal">From my knowledge all that we have is the HV efficiency scan. Even if the tracking is not perfect, it will still show us the correct shape, with the plateau efficiency values. We set the voltages originally using the values found during
commissioning here <a href="https://logbooks.jlab.org/entry/3925085">https://logbooks.jlab.org/entry/3925085</a>. If we look at UV layer 0 (uva_uv_l0_m0) and UV layer 2 (uva_uv_l2_m4) we see that going from 3697 V to 3653 V drops us by about 5% efficiency,
which is fine. But during this last week, with 5 uA on LD2 we usually found UV layer 0 and UV layer 2 running around 70% efficiency. So what should we actually look for to decide that something needs to change?<o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">Best,<o:p></o:p></p>
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<p class="MsoNormal">Sean<o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">On Thu, Nov 18, 2021 at 3:50 PM Gnanvo, Kondo (kg6cq) <<a href="mailto:kg6cq@virginia.edu">kg6cq@virginia.edu</a>> wrote:<o:p></o:p></p>
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<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto">Sean, all
<o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto">There is no reason to change from previous setting. Like Nilanga said, we should stick to the setting we had before.
<o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"> <o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto">The new chamber need HV scan to know the optimal value (don’t assume that it is the same exactly than the other UV layers). You can start with 3653 and see what you get or do a
HV scan. But keep I mind that we need to be careful regarding increasing the HV before we really understand all the consequences in modifying HV divider.
<o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto">If there is no clear reason, to go higher I would be very conservative. That is my default mode<o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"> <o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto">Best regards
<o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto">Kondo<o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"> <o:p></o:p></p>
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<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><b>From:</b> Sbs_gems <<a href="mailto:sbs_gems-bounces@jlab.org" target="_blank">sbs_gems-bounces@jlab.org</a>>
<b>On Behalf Of </b>Holly Szumila-Vance<br>
<b>Sent:</b> Thursday, November 18, 2021 3:45 PM<br>
<b>To:</b> Andrew Puckett <<a href="mailto:puckett@jlab.org" target="_blank">puckett@jlab.org</a>>; Liyanage, Nilanga K (nl8n) <<a href="mailto:nl8n@virginia.edu" target="_blank">nl8n@virginia.edu</a>>; Jeffas, Sean (sj9ry) <<a href="mailto:sj9ry@virginia.edu" target="_blank">sj9ry@virginia.edu</a>>;
<a href="mailto:sbs_gems@jlab.org" target="_blank">sbs_gems@jlab.org</a><br>
<b>Subject:</b> Re: [Sbs_gems] [EXTERNAL] UV GEM HV Settings<o:p></o:p></p>
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<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"> <o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto">3653 for layers 0,2 and new 3. The back tracker has had no changes.
<o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"> <o:p></o:p></p>
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<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><b><span style="font-size:12.0pt;color:black">From:
</span></b><span style="font-size:12.0pt;color:black">Sbs_gems <<a href="mailto:sbs_gems-bounces@jlab.org" target="_blank">sbs_gems-bounces@jlab.org</a>> on behalf of Andrew Puckett <<a href="mailto:puckett@jlab.org" target="_blank">puckett@jlab.org</a>><br>
<b>Date: </b>Thursday, November 18, 2021 at 3:43 PM<br>
<b>To: </b>"Liyanage, Nilanga K (nl8n)" <<a href="mailto:nl8n@virginia.edu" target="_blank">nl8n@virginia.edu</a>>, "Jeffas, Sean (sj9ry)" <<a href="mailto:sj9ry@virginia.edu" target="_blank">sj9ry@virginia.edu</a>>, "<a href="mailto:sbs_gems@jlab.org" target="_blank">sbs_gems@jlab.org</a>"
<<a href="mailto:sbs_gems@jlab.org" target="_blank">sbs_gems@jlab.org</a>><br>
<b>Subject: </b>Re: [Sbs_gems] [EXTERNAL] UV GEM HV Settings</span><o:p></o:p></p>
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<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"> <o:p></o:p></p>
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<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto">Okay, so then what are the recommended settings for ALL UVA layers/modules? I’m confused. Because we have been running with a mix of 3653 and 3697<o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"> <o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto">Andrew<o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"> <o:p></o:p></p>
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<p class="MsoNormal" style="mso-margin-top-alt:auto;margin-bottom:12.0pt"><b><span style="font-size:12.0pt;color:black">From:
</span></b><span style="font-size:12.0pt;color:black">Sbs_gems <<a href="mailto:sbs_gems-bounces@jlab.org" target="_blank">sbs_gems-bounces@jlab.org</a>> on behalf of Liyanage, Nilanga K (nl8n) <<a href="mailto:nl8n@virginia.edu" target="_blank">nl8n@virginia.edu</a>><br>
<b>Date: </b>Thursday, November 18, 2021 at 3:30 PM<br>
<b>To: </b>Jeffas, Sean (sj9ry) <<a href="mailto:sj9ry@virginia.edu" target="_blank">sj9ry@virginia.edu</a>>,
<a href="mailto:sbs_gems@jlab.org" target="_blank">sbs_gems@jlab.org</a> <<a href="mailto:sbs_gems@jlab.org" target="_blank">sbs_gems@jlab.org</a>><br>
<b>Subject: </b>Re: [Sbs_gems] [EXTERNAL] UV GEM HV Settings</span><o:p></o:p></p>
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<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span style="font-size:12.0pt;color:black">HI Sean,</span><o:p></o:p></p>
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<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span style="font-size:12.0pt;color:black"> </span><o:p></o:p></p>
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<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span style="font-size:12.0pt;color:black">No, I think it would be best to run at 3653 V with this modified divider for right now. </span><o:p></o:p></p>
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<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span style="font-size:12.0pt;color:black"> </span><o:p></o:p></p>
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<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span style="font-size:12.0pt;color:black">We are going to study the modified divider with the x_ray source here over the new couple of weeks. Once we know more, we can consider
going higher if needed</span><o:p></o:p></p>
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<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span style="font-size:12.0pt;color:black"> </span><o:p></o:p></p>
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<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span style="font-size:12.0pt;color:black">Best</span><o:p></o:p></p>
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<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span style="font-size:12.0pt;color:black"> </span><o:p></o:p></p>
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<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span style="font-size:12.0pt;color:black">Nilanga</span><o:p></o:p></p>
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<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><b><span style="color:black">From:</span></b><span style="color:black"> Sbs_gems <<a href="mailto:sbs_gems-bounces@jlab.org" target="_blank">sbs_gems-bounces@jlab.org</a>> on behalf
of Sean Jeffas <<a href="mailto:sj9ry@virginia.edu" target="_blank">sj9ry@virginia.edu</a>><br>
<b>Sent:</b> Thursday, November 18, 2021 3:22 PM<br>
<b>To:</b> <a href="mailto:sbs_gems@jlab.org" target="_blank">sbs_gems@jlab.org</a> <<a href="mailto:sbs_gems@jlab.org" target="_blank">sbs_gems@jlab.org</a>><br>
<b>Subject:</b> [Sbs_gems] [EXTERNAL] UV GEM HV Settings</span> <o:p></o:p></p>
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<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"> <o:p></o:p></p>
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<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto">Hi Kondo and Nilanga,
<o:p></o:p></p>
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<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"> <o:p></o:p></p>
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<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto">After we changed the resistor on UV GEM layer 0 back in October Kondo recommended to lower the HV a bit to monitor the GEM HV. Here is the logbook reference <a href="https://logbooks.jlab.org/entry/3930480" target="_blank">https://logbooks.jlab.org/entry/3930480</a>.
However we discovered this week that the voltage has never been returned to 3697 V since then, and we ran all this week at 3653 V. From Kondo's log it is my impression that he meant to only set it to 3653 V for a few hours. Is it ok to change to 3697 V at
this point? Also with the two other UV GEMs in BB we also have these new dividers. Then ran all night at 3653 V with cosmics with no issues. Can we set those to 3697 V as well?<o:p></o:p></p>
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<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"> <o:p></o:p></p>
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<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto">Best,<br>
Sean<o:p></o:p></p>
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