[Sbs_gems] Non-uniform GEM signal timing in BigBite during GMN/GEN

[Andrew Puckett]

Hello all,

As you may remember, we saw that GEM layers 1 and 3 in BigBite exhibited significantly wider timing distributions during GMN (and GEN), even for the good signals. Recently, for the first time, I tried to get a closer look at the uniformity (or lack thereof) of the signal timing for the GEMs, with some interesting findings. I wanted to solicit the opinions of the GEM hardware experts to see if this is something that has been seen before, and if the pattern has a simple explanation, what the physical mechanism might be, and whether it could be mitigated in the future.

The first picture shows the average signal timing (U+V)/2 on the x axis for the five BigBite GEM layers versus global “x” position of the hit on the y axis. As we can see, in UV layers 0 and 2, the timing is relatively uniform as a function of vertical hit position, whereas for layers 1 and 3, there is a significant correlation that follows a similar x dependence. Layer 4 also exhibits an x dependence qualitatively similar to layers 1 and 3 but the magnitude is smaller compared to the resolution. Also, in all cases the width of the good timing peak for layers 1 and 3 is wider (~10 ns) compared to layers 0, 2, and 4 (~6-7 ns), even after accounting for the non-uniformity versus position. The second attachment shows the correlation with the y-coordinate. Here layers 1 and 3 still show a fairly significant correlation while layers 0, 2, and 4 show almost no correlation.

While this is something we can in principle measure and correct for if we want to apply tighter timing cuts in the analysis, I would love to hear people’s ideas for what is happening here. Thoughts?

Best regards,
Andrew

[cid:image001.png at 01D97925.2DE4CAE0]
[cid:image002.png at 01D97926.17335AE0]


Andrew Puckett
Associate Professor, Physics Department
University of Connecticut
196 Auditorium Road, Unit 3046
Storrs, CT 06269-3046
Office phone: (860) 486-7137
https://puckett.physics.uconn.edu
puckett at jlab.org<mailto:andrew.puckett at uconn.edu>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <https://mailman.jlab.org/pipermail/sbs_gems/attachments/20230427/707e2175/attachment-0001.html>
-------------- next part --------------
A non-text attachment was scrubbed...
Name: image001.png
Type: image/png
Size: 1060543 bytes
Desc: image001.png
URL: <https://mailman.jlab.org/pipermail/sbs_gems/attachments/20230427/707e2175/attachment-0002.png>
-------------- next part --------------
A non-text attachment was scrubbed...
Name: image002.png
Type: image/png
Size: 1075420 bytes
Desc: image002.png
URL: <https://mailman.jlab.org/pipermail/sbs_gems/attachments/20230427/707e2175/attachment-0003.png>