sPHENIX HCal discussion

[John Haggerty <haggerty AT bnl.gov>]

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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> >
> > *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