sPHENIX HCal discussion

[Edouard Kistenev <kistenev AT bnl.gov>]

Agree. Temperatures are real must 
Looks like we need copies of your t-sensing toy from in field measurements 
available for wider use. 
As of repeatability with uniplast SiPM holders - tested pretty well - on 
Sunday when t looks rather stable it is  better then. 5%.

Sent from my iPhone

> On Dec 21, 2017, at 11:01 AM, John Haggerty <haggerty AT bnl.gov> 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
>> Facebook <http://www.facebook.com/john.lajoie.5> LinkedIn 
>> <http://www.linkedin.com/pub/john-lajoie/9/a9/bba/>
>> Contact me: Skype john.lajoie
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> 
> -- 
> John Haggerty
> email: haggerty AT bnl.gov
> cell: 631 741 3358
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