Hi Edward,
I don’t recall seeing the MEPHI mapping results from your earlier message, but I may have missed it with my inbox being so full lately. Would you be able to show these at the HCAL meeting Tuesday?
John
From: sPHENIX-HCal-l <sphenix-hcal-l-bounces AT lists.bnl.gov>
On Behalf Of kistenev AT bnl.gov
Sent: Saturday, March 14, 2020 9:54 AM
To: Christopher McGinn <chmc7718 AT colorado.edu>
Cc: HCal sPHENIX <sphenix-hcal-l AT lists.bnl.gov>
Subject: Re: [Sphenix-hcal-l] Fwd: Mapping Hcal Tiles
PS to earlier.
Just not to forget - there is an inherent difference between measurements with LED and measurements with muons or particles. LED light is absorbed close to surface (makes fibers more prominent compared to muon picture) and basically ignores
polystyrene - I am not sure if it involves any scintillations at all - just an attenuation in plastic and absorption in fibers.
We recently got raw muon mapping data for three identical small tiles (S32) from MEPHI (were attached to one of my earlier mails). Two kinds of plastic were used to produce those tiles (bad(1) and god(2)). I wander if someone will get
interested to look into those data and compare the results with what is seen in LED data on large tiles.
Hi, Chris,
Enclosed is my earlier mail to Ron. This would be an easy and rather precise test for the correlation between integral light yield and non uniformity - it excludes fibers.
Edward
Subject: Re: Mapping Hcal Tiles
Date: March 4, 2020 at 4:30:20 PM EST
The question which needs to be answered - are there correlations between integral light yield (measured with muon tester) and tile non uniformity which (for this purpose)
I would be happy to define it as a ratio of the average values measured in 4 corners (four circles 5cm diameter fully superimposed on tile) and characteristic value for a similar circle at the tile CG location (better exclude +-1cm from nearest fibers). While
actual values may depend on your instantaneous device setting, the ratio between two numbers (measured on the tiles of similar geometries) we expect (or want) to stay constant.
Edward
Hi All,
Sorry for the late reply, I've been hoping to catch up with John in person---we're both at WWND this week---but we keep missing each other. I'm glad to help get the test
stand back up and running. The details are probably not so interesting to everyone, so I'll communicate with Jamie privately about that part.
The main bottleneck with the test stand is that a typical OHCal tile scan with ~10,000 scan points takes about ~16-20 hours. Depending on how many tiles need to be tested,
we might consider trying scans with fewer points (the time isn't linear with number of points but this would obviously help).
Hello Megan (cc same),
OK. When Ron is back from WWND next week, we can step through getting our test stand back online. Just then keep me up to date about schedule (when tiles might be shipped,
when results are needed, etc.).
||------------------------------------------------------------------------------------------
|| James L. Nagle
|| Professor of Physics, University of Colorado Boulder
That would be great. I'd like hear from Ron too. I just wanted to comment about your point on the wrapping and the way the tiles are wrapped now. It is relatively easy to
slide the tiles out of the wrapping so that they can slide back into the wrapping and be resealed so I think this is not an issue.
Hello Megan (cc same and Ron),
The test stand here is still in working order, though it might take a bit to remind ourselves how to run things (since Ron and Sanghoon and our undergraduates are now gone).
I am sure that Ron could help us remotely (cc'ing him here too).
Note that we have to remove the black wrapping to run the LED test, but I think we could get something running in the next 2-3 weeks.
Jamie
||------------------------------------------------------------------------------------------
|| James L. Nagle
|| Professor of Physics, University of Colorado Boulder
We see a double peak structure where some set of tiles appears to produce ~20% less light. We see this effect in both the GSU and Uniplast data. Uniplast found that the lower
MPVs correspond to an issue observed in the fibers. Unfortunately, it is not easy to identify this issue visually and was detected after some number of tiles were produced with this lower light yield. The worst tiles were reject by Uniplast but the ones about
~20% lower were sent to GSU. These tiles may be okay to use but we would like to convince ourselves that this issue with the fibers does not cause a uniformity issue within these tiles. We thought the fastest way to test this would be if we could ship some
of these tiles in question from GSU to Colorado for LED mapping testing. Does Colorado still have the capabilities to conduct these measurements? Would someone there be able to run and analyze these tests in the coming weeks?
--
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Chair-elect, RHIC/AGS Users' Executive Committee
Research Scientist, Department of Physics & Astronomy
University of North Carolina at Greensboro
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