[Sbs_gems] [EXTERNAL] UV Latency Analysis Results

[Gnanvo, Kondo (kg6cq)]

Hi Sean,
Thanks for sharing. It think this is great, maybe reducing gas flow will not change much the deformation effect of the readout board because the cause is due to the gas flow scheme of these two layers itself and not overpressure from too high gas flow like the example I share with the SBS prototype last time.
The effect of bulging of the readout board remain the same, so the broadening of the APV25 time will still be noticeable.
It will be good to compare apple to apple when beam is back. This way we can really see if the effect of reducing the gas is more pronounced. I don’t think running the GEM with these gas flow when beam is back will affect the chambers at all.

Ultimately, I also think that we might want to increase the HV on this UV layer 1 and module 1 by 25 V to see the impact on the efficiency. But please don’t change too many thing at the time. Take one run with the same voltage setting that you had before for the beam, so we can compare the pure effect of the gas flow reduction, then change the HV on these two chambers

Best regards

Kondo

From: Sbs_gems <sbs_gems-bounces at jlab.org> On Behalf Of Sean Jeffas
Sent: Saturday, January 15, 2022 11:02 AM
To: Sbs_gems at jlab.org
Subject: Re: [Sbs_gems] [EXTERNAL] UV Latency Analysis Results

Hi All,

We have finished analyzing a cosmic test after turning the gas flow down on layers 1 and 3 from 525 cc/min to 375. The data is attached below. For reference:

Run 13240: Taken January 11th with all four UV layers and 2 uA on LH2 at the SBS-14 kinematic. Gas flow at 525 cc/min
Run 12423: Taken January 14th with cosmic data. UV layers 1 and 3 gas flowing at 375 cc/min

These runs are a bit difficult to compare since one is with beam and the other is comsic, but it's all that we have. Overall you can see that the timing distribution is a bit better for layer 1 and 3, but still not great. Also the efficiencies and gains are not significantly reduced by the lower gas flow. So I think we can run with this setting.

Kondo/Nilanga/Xinzhan: Will this reduced gas flow have a greater effect with the beam on? I suppose we will find out in two hours anyway.

Also I would be interested in turning up the voltage on layer 1 and module 1 in the XY layer by 25 V. Are there any objections?

Best,
Sean

On Thu, Jan 13, 2022 at 3:49 PM Sean Jeffas <sj9ry at virginia.edu<mailto:sj9ry at virginia.edu>> wrote:
Hi Andrew,

I am not sure if you meant to only reply to only me, but here are the plots you asked for. I actually already had them but decided it was kind of overkill.

Best,
Sean

On Thu, Jan 13, 2022 at 3:21 PM Andrew Puckett <puckett at jlab.org<mailto:puckett at jlab.org>> wrote:
Hi Sean,

Interesting results. Another interesting way to visualize these results would be in terms of the strip mean times, which might (or might not) have somewhat better resolution than the time sample peaking distribution. I would also be curious to see a couple of alternative ways of visualizing the data. For example:


  1.  A more “binary” approach: 1D and 2D distributions vs. x and/or y for hits peaking in sample 5 and for hits NOT peaking in sample 5
  2.  Same as 1, but perhaps broken out by hits peaking in samples 1, 2, 3, 4, 5, etc.

Cheers,
Andrew



From: Sbs_gems <sbs_gems-bounces at jlab.org<mailto:sbs_gems-bounces at jlab.org>> on behalf of Sean Jeffas <sj9ry at virginia.edu<mailto:sj9ry at virginia.edu>>
Date: Thursday, January 13, 2022 at 3:03 PM
To: Sbs_gems at jlab.org<mailto:Sbs_gems at jlab.org> <sbs_gems at jlab.org<mailto:sbs_gems at jlab.org>>
Subject: [Sbs_gems] [EXTERNAL] UV Latency Analysis Results
Hi All,

I have finished analyzing the spatial distribution of the peak time samples. I have attached the results below for two runs.

Run 13240: Taken January 11th with all four UV layers and 2 uA on LH2 at the SBS-14 kinematic.
Run 12423: Taken December 1st with J0 still in the layer 1 position but the UV layer was in layer 3 position. This was 2 uA on LD2 at SBS-11.

In the recent run (13240) you can clearly see the peak time sample is uniform over the hit map for every layer except for layer 1 and layer 3. Similarly if you look at the December run (12423) the same issue was present in layer 3, but we never noticed it because we were always the first and last bin out of the analysis. John and I measured the resistors on the GEMs today and did not find a resistance that would suggest that the gas window has collapsed onto the cathode. Unfortunately the shielding blocks us from seeing the gas window, otherwise it would be very easy to tell.

Therefore our current conclusion is that since the GEM layers 1 and 3 both have a non uniform gas flow, this is probably causing some bend in the readout board, which causes this issue. To fix this we can turn down the gas flow rate and see how everything is affected. Since the experiment is down for a few days it would be good to turn it down today and take some cosmic data, if possible.

Best,
Sean
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