sPHENIX HCal discussion

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

Hi John H,

 

Thanks for showing the slides on the iHCAL thermal tests today, it’s great to get that rolling. It makes sense that you see temperatures similar to the oHCAL sectors.

 

What I am having a hard time getting my brain around is what sort of tests we have to do to convince ourselves that we are OK, and whether or not the thermal solution that has been designed for the iHCAL is adequate (or needed?).  As I see it there are two things we need to address:

 

- The LDO’s on the boards at the end of the sector don’t like to get too hot. I think you saw a 60C peak? Obviously with the colling tube and vanes in the bay that will help somewhat but can we put a thermistor on the LDO’s?

 

- The iHCAL is in a different situation than the oHCAL. The oHCAL can just radiate all it’s heat out the back, while the iHCAL is sandwiched between the EMCal and the cryostat.  A standalone sector test that shows temperatures similar to the oHCAL is fine, but what happens when it is installed? I really don’t know how to answer this question. It may be that all the heat is transferred to the frame and exits though the end rings, but I’d feel more comfortable with an expert telling me that was a valid assumption.  In particular I don’t want to find we present some sort of heat load to the cryostat.

 

I absolutely do NOT want to over complicate the iHCAL thermal testing. Before we go further, is there some additional expertise at BNL that we could tap into to sanity check our approach?  If we could get some input that would better define the key tests we have to do we could save a lot of time.

 

Regards,

John

 

John Lajoie

he, him, his

Professor of Physics

Iowa State University

 

(515) 294-6952

lajoie AT iastate.edu