[Sbs_gems] [EXTERNAL] Re: GEM Negative Pulse Overview

[Anuruddha Rathnayake]

Data acquisition for GEM negative pulse study was just completed.

Please see the log entry https://logbooks.jlab.org/entry/3979464 for the
runs taken. I have also updated the SBS RUN LIST spreadsheet.

Best,
Anu



On Sun, Jan 30, 2022 at 4:45 PM Gnanvo, Kondo (kg6cq) <kg6cq at virginia.edu>
wrote:

> Hi Anu,
>
> Yes that should be ok. Anytime from now on is fine.
>
> I just need to inform the shift leader.
>
> Let me know when you are in the CH
>
> Best regards
>
> Kondo
>
>
>
> *From:* Anuruddha Rathnayake <adr4zs at virginia.edu>
> *Sent:* Sunday, January 30, 2022 4:19 PM
> *To:* Gnanvo, Kondo (kg6cq) <kg6cq at virginia.edu>
> *Cc:* Jeffas, Sean (sj9ry) <sj9ry at virginia.edu>; Sbs_gems at jlab.org
> *Subject:* Re: [Sbs_gems] [EXTERNAL] Re: GEM Negative Pulse Overview
>
>
>
> Hi Kondo,
>
>
>
> Since I am on call right now, Ican come in around 5 pm and perform these
> tests.
>
> Let me know if that is okay with you.
>
>
>
> Best,
>
> Anu
>
>
>
>
>
> On Sun, 30 Jan 2022, 16:12 Gnanvo, Kondo (kg6cq), <kg6cq at virginia.edu>
> wrote:
>
> Hi Sean, Anu
>
> We discussed at the RC meeting the afternoon that now (swing or owl shift)
> is the best time to do the studies that you suggested below.
>
>
>
> I was wondering if you and /or Anu will be able to come in and perform
> that study. Any time you will want is ok as.
>
>
>
> Sean: On your suggestion below, you wanted to do it with LH2, however we
> are now taking LD2 data until tomorrow and I assume it is OK to do it with
> LD2 as well (only to adjust the beam current accordingly) right?
>
>
>
> You could sill do 1, 3, 5 and 7 uA on LD2
>
>
>
> Let me know
>
> Best regards
>
> Kondo
>
>
>
> *From:* Sbs_gems <sbs_gems-bounces at jlab.org> *On Behalf Of *Sean Jeffas
> *Sent:* Wednesday, January 26, 2022 4:00 PM
> *To:* Sbs_gems at jlab.org
> *Subject:* [Sbs_gems] [EXTERNAL] Re: GEM Negative Pulse Overview
>
>
>
> Hi All,
>
>
>
> Here is my ideas for doing a GEM study on this:
>
>
>
> *For all runs use GM1_Pedestal configuration (full readout, no zero
> suppression)*
>
> *200k events for all GEMs (should be 3 minutes or less)*
>
> 1) 1 uA on LH2 GEMs at operational HV
>
> 2) 3 uA on LH2 GEMs at operational HV
>
> 3) 3 uA on LH2 GEMs at 1500 V
>
> 4) 5 uA on LH2 GEMs at operational HV
>
> 5) 8 uA on LH2 GEMs at operational HV
>
> 6) 8 uA on LH2 GEMs at 1500 V
>
> 7) 8 uA on LH2 GEMs at 0 V
>
>
>
> Overall this should take about 30 minutes of beam time. Please let me know
> if you have any ideas to change or add something to this.
>
>
>
> Best,
>
> Sean
>
>
>
> On Wed, Jan 26, 2022 at 1:32 PM Sean Jeffas <sj9ry at virginia.edu> wrote:
>
> Hi All,
>
>
>
> I am mostly sending this out because Kondo, Andrew, and Bogdan were not in
> the GEM meeting today and I overviewed the issue of the negative GEM
> signals seen in the hall. I have attached my slides below.
>
>
>
>
>
> https://hallaweb.jlab.org/wiki/images/f/fd/Neg_signal_1_26_22.pdf
>
>
>
>
> At the meeting Ben suggested one interesting reason for why the CM would
> decrease at higher currents, but the fraction of negative pulses would also
> decrease. He suggested that this may happen if the positive signal
> "overrides" a negative signal on the same strip. So at higher currents,
> with higher occupancy, there are less strips with negative signals (because
> they are already positive), decreasing the fraction, but the negative
> signals are still used in the CM calculation, causing the decrease in the
> CM. (Ben, please correct me if I have not described your idea properly).
>
>
>
> Overall we need more data and analysis to understand this problem. We
> should decide on a set of quick runs to study the negative pulses more.
> This will also be simple because Kondo is RC this week. Kondo has already
> suggested a test with HV ~1500V and beam on with online zero suppression
> enabled. I think we should also take some data at different beam currents
> with nominal HV values and the online zero suppression disabled. This can
> be accomplished with 30 minutes of beam time. Please suggest any other
> ideas for tests with beam.
>
>
>
>
>
> For analysis, there are not many options in the analyzer right now to
> study the negative signals. We only have a few predefined histograms saved
> for full readout events, but most of the data is discarded because it is
> not of interest for the tracking. We will need to add some analysis to
> store all the strip information to study this properly. Then we can fully
> see what type of events the negative signals affect on average. We can
> check if they show up in patterns of strips on all the APVs, their
> occupancy, and how they correlate to real signals. Please suggest any other
> analysis ideas for distributions to check.
>
>
>
> Best,
>
> Sean
>
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