sPHENIX HCal discussion

["Lajoie, John G [PHYSA]" <lajoie AT iastate.edu>]

Dear HCAL'ers:

    I wanted to send out a few notes summarizing the issues we discussed in today's HCAL regarding the tile tester. A lot of this was in private emails over the past few days, and even that was confusing, so I thought a summary everyone could digest would be helpful. The experts should correct anything that I get wrong.

(1) The issue we have encountered is that the final production light blocks for the tiles do not plug properly into the mating holder on the tile tester.  The final light blocks were modified so that the SiPM holder "clicks" in place rather than relying on friction, which is a change we definitely need.  There was coordination on the light block and SiPM holder changes, but the impact on the tile tester fell through the cracks.

(2) When the new light block is used on the existing tile tester, there is an additional ~2mm gap between the SiPM and the fibers exiting the tile. The tile tester can still be used, but the amplitude measured from MIPs will be about 20-30% lower.

(3) Since we are interested in relative, not so much absolute, yields when monitoring the Uniplast production, we will continue to use the tile tester at Uniplast as is for the pre-production tiles.

(4) In time for the production option, we will produce modified tile testers with new holders that will properly mate to the production light blocks.  Rich has already started the design work on this, and we will fix other problems at the same time (aluminum pins to replace the printed pins to reduce the risk of breakage, modified screw holes requested by Mike Lenz).

(5) One remaining issue is if the new files testers will use the old SiPM boards or the new boards.  This has downstream implications for the electronics used in the test stand. Megan will work with Edward, Steve Boose, Rich and Mike Lenz to come to a decision on switching to the new electronics.

(6) Uniplast is trying to FedEx new light blocks and SiPM holders to BNL but has shipping issues.  JL is working to get a FedEx number to Uniplast so this can be charged to ISU and we can get these parts to BNL ASAP.  In addition to Rich verifying the light block will work with the new holder design, Eric and Steve need the new SiPM holders to verify the SiPM board size.

(7) Mike Lenz will continue to build the new tests stands with all the parts that don't change, so he will be ready for the new backplanes/holders when they are ready.

(8) Anthony and Edward will communicate with Uniplast about the proper organization of files in Dropbox and will ensure that we are collecting all the information we need from Uniplast, in the way we need it.

John

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John Lajoie

Professor of Physics

Iowa State University

 

(515) 294-6952

lajoie AT iastate.edu