sPHENIX EMCal discussion

[Edouard Kistenev <kistenev AT bnl.gov>]

John,
my immediate comment is about decision to gang on preamp input. I am sure 
that economically (and reliability) wise this is much worse compared to 
simple kluge on the input to digitizer. The only real gain are not preamps 
but cables (x4 smaller cable plant: 1m of cable = 1 preamp) for a cost of 
degraded S/N ratio, loss of reliability (one shortened SiMP may kill 4 
towers), increased susceptibility to rad damage (one SiPM may cover the whole 
shower while 16 will contribute to leakage current) and I may easily come 
with few more no-no's …… We can’t put such proposal on paper without testing 
all performance aspects of it under expected RHIC conditions.  

I don’t think it is even a correct way to address x2 or 3 shortage of funds 
for EMC. If EMC is a real show stopper for the whole sPHENIX - we need to go 
back to the drawing board and consider all options including much deeper 
hybrid EMC/HAD section (spaghetti or shashlik) with space reserved for 
resolution/PId enhancer - say 4X0 preshower which in the end may answer 
concerns of EIC.

                                Edward


> On Jun 30, 2016, at 12:43 PM, John Haggerty <haggerty AT bnl.gov> wrote:
> 
> You probably saw a very similar post to the HCAL list... the questions 
> for the EMCAL are the same, only harder:
> 
> Very soon, we need to agree to changes in the "reference design" of the 
> calorimeters engendered by the descoping exercise.
> 
> In particular, I think the next prototypes we test should be as close to 
> the final design as possible.   In the case of the EMCAL, there are some 
> real questions that we need to answer very soon:
> 
> - Do we even test an eta=1 calorimeter?  No need to test it if we're not 
> going to build it.
> 
> - Do we test "2x2" towers?  Do we have 4 little light guides with a lot 
> of corners, or bigger light guides?  I could imagine a single stuby 
> light guide could result in more uniform light collection, but it's not 
> at all obvious.
> 
> - Do we design preamps that can take 16 SiPM's?  This is a thing that 
> Steve would have to test before we did it, and it would have to be moved 
> to the front burner if we want it for January.
> 
> - Projectivity.  Enough said.
> 
> With the substantial changes to the EMCAL we're talking about, we may 
> also wish to consider delaying our appointment with the FTBF a month or two.
> 
> Since not everyone attends every meeting, I think it's important that we 
> discuss this with a wide audience on the lists.  So fire away.
> 
> -- 
> John Haggerty
> email: haggerty AT bnl.gov
> cell: 631 741 3358
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