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<p class="MsoNormal"><span style="font-size:11.0pt">Hi Andrew, <o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">Thanks for getting back. Yep I agree with the approach you are advancing.
<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">Also I quickly looked at the replay for the high beam current / high rate studies yesterday and I agree that the initial results looks indeed very interesting. The discussion of the results at tomorrow’s meeting
will be very exciting indeed <o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">Best regards <o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">Kondo<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt"><o:p> </o:p></span></p>
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<div style="border:none;border-top:solid #E1E1E1 1.0pt;padding:3.0pt 0in 0in 0in">
<p class="MsoNormal"><b><span style="font-size:11.0pt">From:</span></b><span style="font-size:11.0pt"> Andrew Puckett <puckett@jlab.org>
<br>
<b>Sent:</b> Tuesday, February 8, 2022 1:18 PM<br>
<b>To:</b> Gnanvo, Kondo (kg6cq) <kg6cq@virginia.edu>; Liyanage, Nilanga K (nl8n) <nl8n@virginia.edu>; Rathnayake, Anuruddha (adr4zs) <adr4zs@virginia.edu><br>
<b>Cc:</b> sbs_gems@jlab.org<br>
<b>Subject:</b> Re: Efficiency plots from SBS-14 GEM studies<o:p></o:p></span></p>
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<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal"><span style="font-size:11.0pt">Hi Kondo, <o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">Thanks for putting these plots together, they are very informative. I agree with your interpretation of the efficiency drop in the back layer, it must be caused by an increase of “fake” tracks from the front
four layers. One option I am considering to improve the tracking performance at high rate (for BigBite anyway) is to basically REQUIRE the back GEM layer to be on the track. This of course would lead to a slight drop in overall reconstruction efficiency but
would presumably allow us to reduce the “fake track” fraction quite dramatically. My original presentation about the software to the GEN-II ERR committee basically assumed we would do this. It would allow us to shrink the track search region area at the front
layers by at least a factor of 4 compared to what we are doing now, which relies only on calorimeter information. I started to look at the plots in the logbook from the high current test. They are very interesting. Even though I cannot attend the full GEM
meeting I will try to join for the second half of tomorrow’s meeting after my class is done.
<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">Andrew<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt"><o:p> </o:p></span></p>
<div style="border:none;border-top:solid #B5C4DF 1.0pt;padding:3.0pt 0in 0in 0in">
<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">Sbs_gems <<a href="mailto:sbs_gems-bounces@jlab.org">sbs_gems-bounces@jlab.org</a>> on behalf of Gnanvo, Kondo (kg6cq) <<a href="mailto:kg6cq@virginia.edu">kg6cq@virginia.edu</a>><br>
<b>Date: </b>Monday, February 7, 2022 at 2:31 PM<br>
<b>To: </b>Liyanage, Nilanga K (nl8n) <<a href="mailto:nl8n@virginia.edu">nl8n@virginia.edu</a>>, Rathnayake, Anuruddha (adr4zs) <<a href="mailto:adr4zs@virginia.edu">adr4zs@virginia.edu</a>><br>
<b>Cc: </b><a href="mailto:sbs_gems@jlab.org">sbs_gems@jlab.org</a> <<a href="mailto:Sbs_gems@jlab.org">Sbs_gems@jlab.org</a>><br>
<b>Subject: </b>[Sbs_gems] [EXTERNAL] Efficiency plots from SBS-14 GEM studies<o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-size:11.0pt">Dear all, <o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">I produced a couple of efficiency plots from the GEM scan studies performed during SBS-9 with LD2 with beam current from 1 to 10 uA.
<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt"> <o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">Please check out the attached slides:<o:p></o:p></span></p>
<p class="MsoNormal" style="margin-left:4.8pt"><span style="font-size:11.0pt">1-) Slide 1:
<o:p></o:p></span></p>
<ul style="margin-top:0in" type="disc">
<li class="MsoListParagraph" style="margin-left:0in;mso-list:l4 level1 lfo3"><span style="font-size:11.0pt">on the left: is the GEM current vs. beam current for each of the 8 GEM chambers so basically a different way to look at Anu linearity plots. So of course
the current increases (negative value </span><span style="font-size:11.0pt;font-family:Wingdings">è</span><span style="font-size:11.0pt"> drop on the plots) as the beam current increases and the drop is more significant for the UV layers than the 4 X-Y modules
of the back layer<o:p></o:p></span></li></ul>
<p class="MsoListParagraph"><span style="font-size:11.0pt"> <o:p></o:p></span></p>
<ul style="margin-top:0in" type="disc">
<li class="MsoListParagraph" style="margin-left:0in;mso-list:l4 level1 lfo3"><span style="font-size:11.0pt">On the right: is the efficiency for the same layers vs. beam current. The trend is the similar although not necessarily correlated with the current drop
(or excess current). For example UV layer 3 efficiency drops more faster than the other 3 layers even though the GEM current drop (or excess current) is less pronounced.
<o:p></o:p></span></li></ul>
<p class="MsoListParagraph"><span style="font-size:11.0pt"> <o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">2-) Silde 2:<o:p></o:p></span></p>
<ul style="margin-top:0in" type="disc">
<li class="MsoListParagraph" style="margin-left:0in;mso-list:l4 level1 lfo3"><span style="font-size:11.0pt">This is more interesting, Here I am plotting the efficiency as a function of the excess current (relative to the measured current for 1 uA) for each
chamber<o:p></o:p></span></li><li class="MsoListParagraph" style="margin-left:0in;mso-list:l4 level1 lfo3"><span style="font-size:11.0pt">I keep both x and y axis to the same scale so that we can concentrate on the amplitude of efficiency drop for same range of excess current<o:p></o:p></span></li></ul>
<p class="MsoListParagraph"><span style="font-size:11.0pt"> <o:p></o:p></span></p>
<ul style="margin-top:0in" type="disc">
<li class="MsoListParagraph" style="margin-left:0in;mso-list:l4 level1 lfo3"><span style="font-size:11.0pt">Here, it more interesting to look at the 4 bottom plots for the XY modules where the GEM current drop is less than 10 uA for all 4 modules which represent
less than 1.5% of the nominal GEM so this should not cause any efficiency drop, but we are still looking at 20 percentage point drop at the minimum for each of these modules<o:p></o:p></span></li></ul>
<p class="MsoListParagraph"><span style="font-size:11.0pt"> <o:p></o:p></span></p>
<ul style="margin-top:0in" type="disc">
<li class="MsoListParagraph" style="margin-left:0in;mso-list:l4 level1 lfo3"><span style="font-size:11.0pt">This 20 point drops in efficiency for such small current increase can only be explained by fake tracks from the 4 U-V layer. My hypothesis is that these
fake tracks are partially caused by the negative pulses impact on the common mode calculation
<o:p></o:p></span></li></ul>
<p class="MsoListParagraph"><span style="font-size:11.0pt"> <o:p></o:p></span></p>
<ul style="margin-top:0in" type="disc">
<li class="MsoListParagraph" style="margin-left:0in;mso-list:l4 level1 lfo3"><span style="font-size:11.0pt">Efficiency drop on the 4 UV-module for a excess current range of 10 uA is limited to a couple of percentage point typically less than 5% which is 4 time
smaller and I suspect that the XY layer which is less prone to these negative pulses reduce the probability of fake tracks and therefore the efficiency drop.
<o:p></o:p></span></li></ul>
<p class="MsoListParagraph"><span style="font-size:11.0pt"> <o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">I think this is another clear indication that solving the divider hardware issue is only going to get us that far unless we address the negative pulses issues.
<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt"> <o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">It will also be good that the similar plots are produced for the other GEM studies and correlated with the common mode calculation. I would not have time to do so though
<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt"> <o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">Best regards <o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">Kondo<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt"> <o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt"> <o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt"> <o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">_______________________________________________<br>
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