sPHENIX HCal discussion

[Edward Kistenev <kistenev AT bnl.gov>]

Ron,

I am looking on your pictures with a small tile and wander if small and big tile which you’ve scanned are prepared in a similar ways. They both are not really production tiles, they were mainly to demonstrate the status at a time when they were produced and may have shortcomings. 

Anyway 

- remind me also if tiles came to Colorado with SiPM’s preinstalled or you installed those yourself; 

- remove SiPM boards (carefully) and inspect fibers in the windows - are they clean, are they protruding, if they are centered in a window same way on both tiles. 

If visually the two tiles are fully consistent, use 1mm diameter surgical needle to cut two 1mm diameter pieces of black paper, stick them to transparent tape and place that tape over the fiber exit area. Keep sticky side of scotch tape away from tile.  Do few measurements with LED to see if light from LED still reaches SiPM’s (LED on a side opposite to fibers). Do whatever it takes to kill that light;

- remove your blends and repeat LED scanning;

- plot and compare new pictures;

- plot the signal value measured moving LED along fiber  (opposite of the fiber over the clean side of the tile).

- use your data to compute efficiency of the fiber loops which are expected to act as a mirror. There are three such mirrors on large tile. The small/large difference is one vs three mirrors difference. Maybe do small simulation to check if your results could be affected the difference in fiber routing.

In three months we may be able to build cosmic muon stand using our own hodoscopic tiles (my Chilean hosts are interested in implementing smart tile based solution for sPHENIX).  For now - use LED but make sure your data are not affected by effectively an “ambient light” from LED scattered all  around in your box.

Edward

Edward Kistenev, PhD

PHENIX Physicist