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<p class="MsoNormal">Hi Sean, <o:p></o:p></p>
<p class="MsoNormal">Thanks for the detail answers to my questions. I think we overall agree, it just some definitions that I think we have different understanding to.
<o:p></o:p></p>
<p class="MsoNormal">Please see my additional comments inline starting with +++<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal"><b>From:</b> Sean Jeffas <sj9ry@virginia.edu> <br>
<b>Sent:</b> Monday, February 21, 2022 10:41 AM<br>
<b>To:</b> Gnanvo, Kondo (kg6cq) <kg6cq@virginia.edu><br>
<b>Cc:</b> Sbs_gems@jlab.org<br>
<b>Subject:</b> Re: [Sbs_gems] [EXTERNAL] Negative Pulse Analysis Update<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<div>
<p class="MsoNormal">Hi Kondo,<o:p></o:p></p>
<div>
<p class="MsoNormal"><o:p> </o:p></p>
</div>
<div>
<ol start="1" type="1">
<li class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto;mso-list:l8 level1 lfo1">
Yes I am removing the highest 54 and lowest 54 ADC channels. So yes I agree that this removes the negative pulse effect. Is this not what we want in order to correctly calculate the CM?<o:p></o:p></li></ol>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto">+++ Yes, that the way to calculate the CM taking into account the negative pulses. My point here is that even though sorting is far better to address the negative pulses than Danning’
method, It is not perfect and the less channels you use to calculate the CM (i.e 20) the less precise your correction will be. You can check that with a plot of CM (7uA) – CM (pedestal data) as a function of how many channels you use (from 20 to 80) for example<o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto">+++ BTW, here I hope that before you compute CM, you correct for the pedestal offset before
<span style="font-family:Wingdings">è</span> This order becomes critical here since you are removing both negative and positive pulses
<o:p></o:p></p>
<ol start="2" type="1">
<li class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto;mso-list:l8 level1 lfo1">
My apologies, on slide 5 I talk about old and new CM calculation methods. The left and right plots are supposed to be the same, but compare between the old and new methods. But this slide is already outdated, since Andrew has developed a new online CM algorithm
that seems even better, and he will update about this later.<o:p></o:p></li></ol>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto">+++ Ok, I understand, but to be precise, what you are plotting on the Y axis is it CM (danning) – CM (sorting) and which one is the old (left plot or right) and which one is the
new? <o:p></o:p></p>
<ol start="3" type="1">
<li class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto;mso-list:l8 level1 lfo1">
The only ways I know to definitely prove a baseline shift is to plug an oscilloscope into the output and look at it with beam or to correctly measure the CM baseline during beam and compare to the pedestal levels. It is too late for the oscilloscope option
but we can measure the baseline from the full readout events. Unless someone has a better suggestion, the only way to "prove" the CM is calculated correctly is to visually look and see how the result compares to the raw strip data. I have done this using the
event displays here, <a href="https://logbooks.jlab.org/entry/3984280" target="_blank">https://logbooks.jlab.org/entry/3984280</a>. Specifically you can look at this run, which I zoomed in the axis to make things even more clear, <a href="https://logbooks.jlab.org/files/2022/02/3984280/CM_event_display_run13602_zoomed_0.pdf" target="_blank">https://logbooks.jlab.org/files/2022/02/3984280/CM_event_display_run13602_zoomed_0.pdf</a>.
I think from all this data it is clear that the sorting method gives a CM result that is within 15 ADC of the true baseline. Then when we compare the sorting method results over different beam currents we see the CM offset increase up to -35 ADC, <a href="https://logbooks.jlab.org/files/2022/02/3984417/neg_pulse_study_3.pdf" target="_blank">https://logbooks.jlab.org/files/2022/02/3984417/neg_pulse_study_3.pdf</a>.
Therefore I see no other explanation than the APV baseline is truly shifting downwards while the beam is on.<o:p></o:p></li></ol>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto">+++ Here it will be good if you define:
<o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto">+++ what you mean by true baseline? Is it the baseline you get from pedestal data after correcting for the CM?
<o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto">+++ when you say CM is within 15 ADC of the true baseline, what do you mean? is that statement true for any beam current?
<o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto">+++ CM offset increases up to -35? What does that mean?
<span style="font-family:Wingdings">è</span> baseline shift is only relevant w.r.t different time beam of the same APV and the same event, It is not with respect to any “true baseline” level, the CM offset parameter is precisely the magnitude of the correction
you apply to the baseline shift it does not matter if it is -15 or -35 as long as you can calculate it properly and it is.
<o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto">+++ The point I was making to Ben at the meeting last week is that if the shift is a baseline shift, then it does not matter what cause it or even understand its source as you can
correct it. If it is shift for individuals channels in the APV because of high rate and large signal (which I observe with APV data) then it also does not matter because these channels are not used for the CM calculation<o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto">+++ Do you have a plot of average CM (new calculation) as a function of the beam current
<o:p></o:p></p>
<ol start="4" type="1">
<li class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto;mso-list:l8 level1 lfo1">
I selected one MPD from the front most UV layers, which naturally has the most background. One MPD on a UV layer covers half of the active area, so this does cover the hottest region of the detectors.<o:p></o:p></li><li class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto;mso-list:l8 level1 lfo1">
You are right, I have not thoroughly investigated the possibility of the entire hit being flipped. I have only looked at a hit flipping within the 6 time samples. I am still working on using tracking to check for negative hits in "expected" areas of the detectors.
I will just say that from my plots of "APV Negative Signal Peak Time" we do not see a normal pulse shape. But of course this could be due to saturation. or something else.<o:p></o:p></li><li class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto;mso-list:l8 level1 lfo1">
My apologies, my wording was not correct here. My conclusion should be more like "There is no evidence of positive signals flipping into negative signals inside of the trigger window". As you mentioned there is also the scary possibility that the negative strips
are not hits, but they "occupy" the strip and do not let positive hits in the same location be recorded. This can be investigated by checking if positive clusters ever have a "break" in the middle from negative strips. Or perhaps anyone else has a suggestion.<o:p></o:p></li></ol>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto">+++ Yes and this was my actual initial worry in October when we observe the negative pulses for the first time, l whether it is polarity flip or not, the strip is occupied by a
wrong signal. I became aware of the second problem i.e. CM correction later, but I am less worried about this one because it can be dealt with “easily”<o:p></o:p></p>
<ol start="7" type="1">
<li class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto;mso-list:l8 level1 lfo1">
Wouldn't the negative pulses saturate at 0? Or am I misunderstanding something? <o:p></o:p></li></ol>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto">+++ The “0” here is your baseline that level is set through some register that you configure. So you optimize this level to increase the dynamic range for the polarity of the signal
you want to measure, then you automatically limit the range for the opposite signal (which is negative on the plots here), so no matter how large is the pulses (whether it is real signal or not) it will be limited by the 200 – 400 ADCs unlike the positive
pulses that can go up to 2000 ADCs … <span style="font-family:Wingdings">è</span> that is why the analysis between positive and negative pulse i.e your 2D correlation plots are biased. At least that is my understanding, maybe I am wrong on some details but
Ben can correct me <o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"> Any way the most important thing is to have a strong CM algorithm that deals with negative pulses and it looks like you and Andrew are making progress so I just raise points to
understand the phenomenon we are seeing. It is not criticism<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>
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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 Fri, Feb 18, 2022 at 7:04 PM Gnanvo, Kondo (kg6cq) <<a href="mailto:kg6cq@virginia.edu" target="_blank">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">Hi Sean,
<o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto">Thanks for the studies. It is pretty extensive and a lot of information to digest so probably I am still missing a few things, so maybe l can ask a couple of few points that might
help clarify a little bit things. <o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"> <o:p></o:p></p>
<ol start="1" type="1">
<li class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto;mso-list:l3 level1 lfo2">
You use only 20 middles channels to calculate CM using the sorting method, meaning that you remove the 54 highest ADC channels and 54 lowest ADC channels from the calculation
<span style="font-family:Wingdings">è</span> Is that correct? If so, yes this will probably remove the negative pulse effect in almost all cases even though the precision of CM calculation will be strongly affected by definition<o:p></o:p></li></ol>
<p> <o:p></o:p></p>
<ol start="2" type="1">
<li class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto;mso-list:l9 level1 lfo3">
What is the difference between the 2 plots of slide 2 in attached pdf. I see the same title in the y axis
<span style="font-family:Wingdings">è</span> is it typo where you meant Danning CM – baseline CM (on left) and sorting CM – baseline CM (on right), baseline meaning the CM calculated from pedestal data (ideal case?)
<o:p></o:p></li></ol>
<p> <o:p></o:p></p>
<ol start="3" type="1">
<li class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto;mso-list:l7 level1 lfo4">
Do you actually have any evidence from the data of the voltage shift downward due to high occupancy and why is it an issue w.r.t to CM correction?
<o:p></o:p></li></ol>
<p> <o:p></o:p></p>
<ol start="4" type="1">
<li class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto;mso-list:l6 level1 lfo5">
Even for the 7uA on LD2 data that you are showing, I don’t really see high occupancy data, and since you said that you analyzed data from only 1 MPD, did you select MPD reading out data from the hottest area of the chamber?
<o:p></o:p></li></ol>
<p> <o:p></o:p></p>
<ol start="5" type="1">
<li class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto;mso-list:l1 level1 lfo6">
In my view, there are several aspect of what I mean by polarity flip. <o:p></o:p></li></ol>
<ol start="5" type="1">
<ol start="1" type="a">
<li class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto;mso-list:l1 level2 lfo6">
It looks to me like you are looking for a flip for a same strip across the 6 time sample. This is just one way, but very likely the most unlikely<o:p></o:p></li><li class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto;mso-list:l1 level2 lfo6">
On slide 1 of the attached pdf, you can clearly see an event with have both positive ADC strips and negative ADC strips on the same APV. The question is are the negative signal flip or not? Unless these strips are always below the baseline (i.e. their pedestal
level, which we al agree it is not the case), something makes them flip their ADC level w.r.t the baseline while there was good hit in other strips of the same APV<o:p></o:p></li></ol>
</ol>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"> <o:p></o:p></p>
<ol start="6" type="1">
<li class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto;mso-list:l0 level1 lfo7">
Even if there is never an actual signal flip, with your correct conclusion that the negative pulse occupancy increases in similar fashion than the positive one. I think regardless whether we convince ourselves that signal can flip or not:
<o:p></o:p></li></ol>
<ol start="6" type="1">
<ol start="1" type="a">
<li class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto;mso-list:l0 level2 lfo7">
it is not correct to say that negative pulse does not cause the loss of positive pulse
<o:p></o:p></li><li class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto;mso-list:l0 level2 lfo7">
there is a high probability that a good event hitting these strips might be lost (because of negative occupancy) and I think that is the scariest scenario.
<o:p></o:p></li></ol>
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<p> <o:p></o:p></p>
<ol start="7" type="1">
<li class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto;mso-list:l4 level1 lfo8">
Most negative pulses have the same amplitude across time sample can be just due to saturation, there are actually some case where they have the typical APV signal waveform (see slide 3)<o:p></o:p></li></ol>
<p> <o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto">Any way these are just a few questions I have after looking at the results you present.
<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>
<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>Sean Jeffas<br>
<b>Sent:</b> Friday, February 18, 2022 4:31 PM<br>
<b>To:</b> <a href="mailto:Sbs_gems@jlab.org" target="_blank">Sbs_gems@jlab.org</a><br>
<b>Subject:</b> [Sbs_gems] [EXTERNAL] Negative Pulse Analysis Update<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">Hi All,<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">I touched up my negative pulse analysis results that I showed to everyone last week. I realized I was making a serious mistake by simply cutting on signal > 80 ADC, because the
first few strips in the APV always have large signals on them from the event header. Therefore this was significantly skewing my data. I am now using the correct method of cutting using 5*sigma of the pedestal noise, as is done in the tracking analysis.<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">Please see my new results in the following slides
<a href="https://logbooks.jlab.org/files/2022/02/3984417/Neg_pulse_study_2_18_22.pdf" target="_blank">
https://logbooks.jlab.org/files/2022/02/3984417/Neg_pulse_study_2_18_22.pdf</a>. Also please take the time to look over all the plots in my log entry, <a href="https://logbooks.jlab.org/entry/3984417" target="_blank">https://logbooks.jlab.org/entry/3984417</a>.
I try my best to pick some event examples to show, but I encourage everyone to scroll through the event displays I have posted, to get an idea of what the negative pulses look like. Please let me know your thoughts and questions.<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,<o:p></o:p></p>
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<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto">Sean<o:p></o:p></p>
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