sPHENIX HCal discussion

[Kistenev <kistenev AT bnl.gov>]

Hello Friends,

thank you for the data, we’ll definitely need better quality control and we’ll need it in place where tiles are produced. 

The 5% visible light yield grows at the tile edges is certainly cladding light, it would probably be higher if we used double clad fibers. With single clad fibers cladding light is not such a big problem.

Drop of the light yield very close to the edge of the tile is probably the effect of the uncertainty in the source position with respect to the edge on the left and on the right.

The >20% right-left difference in the coated base tile is alarming. Such things are not unheard of or unseen. Tiles are extruded from dry mix of fluors and polystyrene. If mix is not absolutely uniform or melt temperature or extrusion rate are not stable during the time of extrusion - we will see this effect. I do not know the size of individual load, I do not know the total tile area produced with a single load mix but I will ask.  It all can be brought under control (even if the final impact on detector performance is unlikely to be dramatic), the problem is to bring this control close to the start of production line and to control controllers. Not excluded that at the end we’ll need to walk the road of PbSc - develop procedures and tools, ship tools to Uniplast, teach couple operators and ask for availability of control data from every production stage. 

Edward

PS. Technical suggestion - please use the same coordinate systems (and units) in all pictures (better be [cm]). Please also plot a lateral distribution - this will be our first data related to the light propagation in tile, not in fibers.

On May 29, 2015, at 1:13 PM, Jamie Nagle <jamie.nagle AT colorado.edu> wrote:

Hello All,

Here are summary slides from Sebastian and Sebastian at Colorado on our tests this week.    It does seem that some of these light variation features are issues in the panel - in particular see the picture of the fibers in the grooves.    John is sending us new SiPMs and pre-amps and we can repeat these tests with the new equipment next week.   

Sincerely,

Jamie

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|| James L. Nagle   
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