sPHENIX HCal discussion

[John Lajoie <lajoie AT iastate.edu>]

Hi Jamie,

    With these short panels, I would guess that they are extruded, coated and then cut and polished? Maybe the non-uniformity has something to do with the cutting the panels to shorter lengths?

regards,
John

On 5/21/2015 10:37 AM, Jamie Nagle wrote:

Hello Edward et al.,

We should have a new set of full results to send around early next week.   We did find on the Control Panel (panel #10 in the slides) with the uniform coating the following results...

1.   The light response is non-uniform across the top fiber (the one separated from the three others).   In fact, it looks like a 10% light drop near one end and a 10% light increase near the other -- not a linear change in light response.

2.  Simply switching the panel around and leaving the SiPMs, triggers, etc. alone, the light response switched around -- i.e. implying that this is something in the panel itself.

3.  They also ran the same test on the 3rd fiber (in the middle of the group of 3), and got the same effective non-uniformity and in the same direction.

We wonder if this might be a non-uniformity in the how the coating is applied, or maybe something in the gluing of the fibers (more glue on one side?).   

We want to test a couple other "Control Panels".    My question is in the slides, Panel #1, #2, and #3 I believe have a uniform white coating.   They are wrapped in foil, black paper...    Can we take this foil/paper off?    I worry that if the foil or paper are non-uniform, they will introduce additional confusion.   

Sincerely,

Jamie

On Mon, May 11, 2015 at 5:05 PM, Jamie Nagle <jamie.nagle AT colorado.edu> wrote:

Hello Edward (cc sphenix-hcal-l list and Shawn, Sebastian, Sebastian),

We just received the shipment of HCal scintillator tiles at the University of Colorado today!     In the attached slides we have cataloged the different panels by the markings on the plastic cover and the visible coating patterns.   We do not want to remove the wrapping under the plastic cover on some of the tiles before learning more.

A full scan with detailed resolution will probably take about one-day per tile.     Additionally, all tiles in the past have had the fibers extending beyond the end and that is where we coupled the SiPM to the fiber.  On all of these panels the fibers are cut flush to the scintillator end, and it is not so clear they are polished.    We can put together a coupling device, though are concerned that the optical grease we have been using is known (by our experience) to eat away at the white coating (the exact material properties we are not aware of).    A quick answer to this question would be great to get a first test underway.

It would be great if we can set up a separate meeting or part of the larger HCal meeting, to go through the optimal testing of these tiles.    For example, we can easily run with a two SiPM coincidence on the ends of one fiber as long as we can use optical grease, and are unclear on the 4 fibers purpose in each tile.

Sincerely,

Jamie (for Shawn, Sebastian, and Sebastian)

 

||--------------------------------------------------------------------------------
|| 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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||--------------------------------------------------------------------------------
|| 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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John Lajoie

PHENIX Deputy Spokesperson

Professor of Physics

Iowa State University

 

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