[Sbs_gems] [EXTERNAL] Negative Pulse Analysis Update

[Gnanvo, Kondo (kg6cq)]

Hi Sean,
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.


  1.  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 ==> 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



  1.  What is the difference between the 2 plots of slide 2 in attached pdf. I see the same title in the y axis ==> 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?)



  1.  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?



  1.  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?



  1.  In my view, there are several aspect of what I mean by polarity flip.
     *   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
     *   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


  1.  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:
     *   it is not correct to say that negative pulse does not cause the loss of positive pulse
     *   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.



  1.  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)


Any way these are just a few questions I have after looking at the results you present.

Best regards
Kondo

From: Sbs_gems <sbs_gems-bounces at jlab.org> On Behalf Of Sean Jeffas
Sent: Friday, February 18, 2022 4:31 PM
To: Sbs_gems at jlab.org
Subject: [Sbs_gems] [EXTERNAL] Negative Pulse Analysis Update

Hi All,

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.

Please see my new results in the following slides https://logbooks.jlab.org/files/2022/02/3984417/Neg_pulse_study_2_18_22.pdf. Also please take the time to look over all the plots in my log entry, https://logbooks.jlab.org/entry/3984417. 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.

Best,
Sean
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