sPHENIX HCal discussion

[kistenev AT bnl.gov]

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.

Edward

On Mar 14, 2020, at 10:38 AM, <kistenev AT bnl.gov> <kistenev AT bnl.gov> wrote:

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

Begin forwarded message:

From: kistenev AT bnl.gov

Subject: Re: Mapping Hcal Tiles

Date: March 4, 2020 at 4:30:20 PM EST

To: Ron Belmont <belmonrj AT gmail.com>

Cc: Jamie Nagle <jamie.nagle AT colorado.edu>, Megan Connors <meganeconnors AT gmail.com>, Dennis Perepelitsa <Dennis.Perepelitsa AT colorado.edu>, John Lajoie <lajoie AT iastate.edu>

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

On Mar 4, 2020, at 3:52 PM, Ron Belmont <belmonrj AT gmail.com> wrote:

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).

Cheers,

Ron

On Wed, Mar 4, 2020 at 1:45 PM Jamie Nagle <jamie.nagle AT colorado.edu> wrote:

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.).

Sincerely,

Jamie

||------------------------------------------------------------------------------------------
|| James L. Nagle    
|| Professor of Physics, University of Colorado Boulder

|| EMAIL:   jamie.nagle AT colorado.edu 
|| SKYPE:  jamie-nagle         
|| WEB:      http://spot.colorado.edu/~naglej  
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On Tue, Mar 3, 2020 at 10:36 AM Megan Connors <meganeconnors AT gmail.com> wrote:

Hi Jamie,

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.

Best, 

-Megan

On Tue, Mar 3, 2020 at 12:29 PM Jamie Nagle <jamie.nagle AT colorado.edu> wrote:

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.

Sincerely,

Jamie

||------------------------------------------------------------------------------------------
|| James L. Nagle    
|| Professor of Physics, University of Colorado Boulder

|| EMAIL:   jamie.nagle AT colorado.edu 
|| SKYPE:  jamie-nagle         
|| WEB:      http://spot.colorado.edu/~naglej  
||------------------------------------------------------------------------------------------

On Tue, Mar 3, 2020 at 10:21 AM Megan Connors <meganeconnors AT gmail.com> wrote:

Dear Jamie,

During today's HCal meeting, GSU showed the most recent performance distributions. (https://indico.bnl.gov/event/7802/contributions/35479/attachments/26886/40939/HCal_Meeting_March__3rd.pdf) 

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? 

Best, 

-Megan 

-- 

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Ron Belmont (he/him/his)

Chair-elect, RHIC/AGS Users' Executive Committee

Research Scientist, Department of Physics & Astronomy

University of North Carolina at Greensboro

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