[Sbs_gems] [EXTERNAL] UV Latency Analysis Results

[Sean Jeffas]

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> 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> 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> on behalf of Sean Jeffas <
>> sj9ry at virginia.edu>
>> *Date: *Thursday, January 13, 2022 at 3:03 PM
>> *To: *Sbs_gems at jlab.org <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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