sPHENIX HCal discussion

[Jamie Nagle <jamie.nagle AT colorado.edu>]

Hello sPHENIX HCal'ers,

Here is a brief update on progress with the Colorado test station and some questions/issues to consider.

* Sebastian, Sebastian, and now Ron Belmont have made progress on the test station.    We originally received two of the new pre-amps - one worked fine and the other was drawing a large current.   Steve sent us a replacement pre-amp, which is working fine - so we have a complete set up.    Steve do you want us to send back the pre-amp that was drawing a large current?

* The system is now well shielded and that has resolved the large noise pickup problem we were having with the new electronics.   We now see clear p.e. peaks with the source and LED tests.

* We received the model information from Steve Boose for two PE calibrating LEDs (Newark brand part #UV3TZ-405-15 for the 15 degree viewing angle and Newark brand part #UV3TZ-405-30 for the 30 degree viewing angle). We've ordered and received these and are now using them to calibrate our results to photoelectrons and to test response across the panel.  We will see if we can reproduce the LED test results from the BNL station as reported by Rusty's students a couple of weeks ago.  One nice feature is that we can turn the LED up (it is collimated in a tube) and get a signal through the white coating.

* The mounting brackets were 3-d printed and are being used.   The mounting holes do not fit the panels.   Right now we have them connected via an outer brace - seems okay though not optimal.    The suggestion that we can modify the bracket drawing ourselves is something we are pursuing at a low level - this does not seem the optimal way forward.

We still need to turn this progress into a new set of results on these 4 fiber short panels from Uniplast with the LED and source.    We are stepping through methodically to understand the reproducibility of each test.  

Things to consider....   The panels from Uniplast are somewhat problematic.   The uniformity of the placement of the fiber in the groove, the position of the groove, the coating on the panel is not very good.    These issues can be seen by eye and are true in all the panels.    This also means that the mounting brackets are hard to match to a clear specification.   What is the schedule for next round prototype panels from Uniplast?  

It might be a good idea to get a set of panels from another vendor at least for comparison.    Is there a status on the Fermilab option that we can help to follow up on?    What about just comparing with a couple panels from Saint-Gobain with precision machined grooves?    Even if the latter is not an option for full production, just having a good reference and understanding the relative performance would be helpful.

Sincerely,

Jamie (for Sebastian, Sebastian, Ron)

--

||--------------------------------------------------------------------------------
|| 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 
||---------------------------------------------------------------------------------