sPHENIX HCal discussion

[John Haggerty <haggerty AT bnl.gov>]

I went ahead and put SiPM's on 15 of the 16 inner HCAL towers (60 of 64 
tiles) sorted by Vop.  I couldn't do the last tower--I had two SiPM 
holders which failed my Q/A testing (no SiPM) and two that had no 
recorded Vop that I could find.  You can see pictures here:

> https://photos.app.goo.gl/aonmy19NENH72jLy1

The only thing I should mention as a possible concern is that some of 
the SiPM holders seem to a little bit offset from the edge of the tile 
even though they all have Richie's square washer to prevent the setscrew 
from protruding through the holder.  (There are some closeups in the 
album that show that situation.)  They could still have the same 
SiPM-fiber distance, I don't see an easy way to check, and it probably 
doesn't matter that much.  I'll get the attached map in the spreadsheet 
soon.  Thanks to Sal for putting the SiPM assemblies together and to 
Mike Lenz for helping me get set up.

On 12/22/17 10:20 AM, John Haggerty wrote:
> Edward,
>
> Yes, we have the SiPM's grouped by Vop, although they are very close 
> (the list I have and will post later goes from 68.48 to 68.50).
>
> On 12/22/17 8:34 AM, Edouard Kistenev wrote:
> > Hi John, I would rather say yes and no. We do not need to group tiles 
> > but we really need to group sipm’s.  As for tiles - this batch is a 
> > bit specials - we kind of raised hell seeing x2 spread in the 8 signal 
> > samples so the main body of this contract got  a lot of attention. 
> > Would be good to keep this awareness alive for the whole project. If 
> > on site control will keep tile to tile spread bellow 10% and tile 
> > luminosity known and sipm’s are rematched on a similar scale then all 
> > what is left is one scaling coefficient to get detector calibrated.
> >
> > Sent from my iPhone
> >
> > On Dec 21, 2017, at 2:48 PM, John Lajoie <lajoie AT iastate.edu 
> > <mailto:lajoie AT iastate.edu>> wrote:
> >
> > > Hi John, Edward:
> > >
> > >     Thanks for the discussion. I don't remember seeing anything from 
> > > previous test beams on the variation of scintillator slats within a 
> > > tower, but Abhisek did make a plot of the deviation of the cosmics 
> > > response for *towers* for the 2017 test beam setup, normalized to the 
> > > simulation to take out the geometry effect.  I'm attaching that here 
> > > as this is something that we might want to compare with this year.
> > >
> > >     It sounds like we really don't need to worry about grouping 
> > > tiles+SiPMs for the inner HCAL for this test beam.
> > >
> > > Regards,
> > > John
> > >
> > >
> > > On 12/21/2017 10:01 AM, John Haggerty wrote:
> > > > Edward et al.,
> > > >
> > > > I copied to root files off the laptop to
> > > >
> > > > > /direct/sphenix+data+data03/phnxreco/sphenix/caen5702/ihcaltiles
> > > >
> > > > You probably have notes on files-to-tiles which we might want to put 
> > > > with them.
> > > >
> > > > I agree that if the tile-to-tile variation is "about the same" as 
> > > > the variation with in a tile, that there would be no point to 
> > > > sorting the tiles by light output.  I couldn't find or make a 
> > > > histogram of the variation in light output of last year's small 
> > > > tiles form the tile mapper, maybe someone on this list has that 
> > > > handy, that would provide quantitative comparison to this.
> > > >
> > > > One could also question whether the precision that the tile-to-tile 
> > > > variation can be measured without being extremely meticulous about 
> > > > the coupling of the SiPM to the fibers, the temperature of the 
> > > > SiPM's, and the amplifier gain variation.  I know you've tried to be 
> > > > careful, but even so, if the tiles are the same within the 
> > > > measurement errors, it seems unnecessary to sort the tiles.
> > > >
> > > > So does all the evidence point to putting the tiles together?  I can 
> > > > imagine a number of possibilities for cosmic testing that would give 
> > > > us some additional information on variation once they're in the 
> > > > absorber.
> > > >
> > > > On 12/20/17 6:11 PM, Edward Kistenev wrote:
> > > > > Hi, John,
> > > > > I am done with 2017 testing of tile to tile uniformity. Cosmic data 
> > > > > in some form are  available for 24 tiles of HInner calorimeter. 
> > > > > After all other testing and tweaking 12 tiles of one configuration 
> > > > > (S30)  were used to equalize the channel gains in the CAEN box I am 
> > > > > currently using. They were then removed and 12 new randomly chosen 
> > > > > tiles of a different configuration (S32)  were then placed into the 
> > > > > same kluge.  Both data taking runs were made under the same running 
> > > > > conditions and resulted in essentially identical numbers (peak 
> > > > > positions, see two pictures below - before and after).  The ratio 
> > > > > is 1.01 with rms of 10%. This is essentially a very good upper 
> > > > > limit to configuration dependence of the light yield and 
> > > > > tile-to-tile spread we have for the small tiles in the recent batch 
> > > > > as it came from UNIPLAST. Its contribution to HInner induced 
> > > > > constant term is certainly lower then that “estimated” as due to 
> > > > > 20% across the tile non-uniformity or LCG fluctuations in 
> > > > > calorimeter with depth dependent sampling fraction (which can be 
> > > > > accounted for on event-by-event basis).
> > > > > My best guesstimate for today is that we do not need tile grouping 
> > > > > for this prototype, visual inspection of fiber luminosity when tile 
> > > > > is out of its protective wrap should be sufficient to answer 
> > > > > live/dead question after shipment.
> > > > > And we will definitely pay attention to tile-LED data when they 
> > > > > will be available in January.
> > > > > Edward
> > > > >
> > > > >
> > > > >
> > > > >
> > > > >
> > > > > On Dec 20, 2017, at 4:32 PM, John Lajoie <lajoie AT iastate.edu 
> > > > > <mailto:lajoie AT iastate.edu>> wrote:
> > > > >
> > > > > Dear HCAL'ers:
> > > > >
> > > > >      In the HCAL meeting today we had a discussion of the assembly 
> > > > > of the inner HCAL for the test beam, the testing of the tiles, and 
> > > > > whether or not it would be valuable to try to match cosmics 
> > > > > response of the HCAL tiles within a tower.  In principle this 
> > > > > should be a "good thing", and I would imagine that if there is a 
> > > > > large variation between the tiles in a tower that could contribute 
> > > > > to the constant term in the energy resolution.
> > > > >
> > > > >      Doing this would require mating the scintillators with their 
> > > > > SiPM's followed by cosmics testing to mix-and-match the 
> > > > > scintillators before they are installed. It's my understanding that 
> > > > > at BNL they will be ready to start installing scintillator soon, so 
> > > > > if we want to do this then we need to get organized quickly.  Of 
> > > > > course, we would only be doing this for the inner HCAL as the outer 
> > > > > HCAL is the same as last year.  I think I would be assassinated if 
> > > > > I suggested we disassemble the outer HCAL and match the tiles.
> > > > >
> > > > >      In past test beams the variation within a tower was not 
> > > > > carefully controlled, so if we did this it would be a good way to 
> > > > > test the effect on the energy resolution. However, if we only do it 
> > > > > for the inner HCAL it is likely of limited utility.
> > > > >
> > > > >      Comments? Suggestions?
> > > > >
> > > > > Regards,
> > > > > John Lajoie
> > > > >
> > > > >
> > > > > *John Lajoie*
> > > > > Professor of Physics
> > > > > Iowa State University
> > > > >
> > > > > (515) 294-6952
> > > > > lajoie AT iastate.edu
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> > > > > <http://www.linkedin.com/pub/john-lajoie/9/a9/bba/>
> > > > > Contact me: Skype john.lajoie
> > > > >
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> > > > >
> > > > > <x-msg://13/#DAB4FAD8-2DD7-40BB-A1B8-4E2AA1F9FDF2>
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> > >
> > >
> > > *John Lajoie*
> > >
> > > Professor of Physics
> > >
> > > Iowa State University
> > >
> > > (515) 294-6952
> > >
> > > lajoie AT iastate.edu
> > >
> > > Facebook <http://www.facebook.com/john.lajoie.5> LinkedIn 
> > > <http://www.linkedin.com/pub/john-lajoie/9/a9/bba/>
> > > Contact me: Skype john.lajoie
> > > <HCAL_tower_variation_KPP.png>
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--
John Haggerty
email: haggerty AT bnl.gov
cell: 631 741 3358

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