sPHENIX HCal discussion

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

Hi John, 

Uniplast is going to move ahead and make the new B25 tiles for the 
preproduction. We have the "old" B25's at GSU. I certainly don't disagree 
that we could test on a single sector (as suggested previously).   We have a 
bit before they will begin production, so we can discuss this at the next 
HCAL meeting. 

I really appreciate the attempts at problem solving - but you have to take a 
step back and ask if this is a problem you want to *choose* to solve, because 
it is a choice.  We have a design (for B25 and the rest of the calorimeter) 
that has been vetted in countless internal reviews and meetings over the past 
several years. In fact, we explicitly sat down and reviewed the tile changes 
that were made to avoid interference with the combs. Some may want to call 
into question the new fiber routing but at the time confidence was expressed 
that this would not make a difference. 

At this stage all decisions must be *evidence-based*, and right now I'm 
hearing a lot of opinions expressed but none of it is backed up by hard 
facts.  Before we even start down this road we should have some idea what we 
thing we can gain - because we don’t *have* to change from our existing 
design and plan! We just wait a little bit and Uniplast will provide the 
tiles as specified. 

The performance of the HCAL doesn't depend on the exact location of the 
preamp, so the only argument I have heard so far for doing this is the 
possibility that the older B25 has a better light collection.  Prove it and 
then we'll talk - and as quantitative matter show me that the difference 
between the old and new tiles is larger than the 20% light yield variation we 
had in the test beam prototype, which met spec for the physics we want to do. 

You're opening a can of worms here - why would we do this for just B25? Why 
not all the tiles? Why not a perpetual R&D cycle? The answer is that time and 
time again we have demonstrated that the performance of the oHCAL is more 
than good enough for the physics it is designed to do.  At this point it's 
not our job to continue to optimize, we should focus on building what is 
spec'd. 

Regards,
John 

-----Original Message-----
From: John Haggerty <haggerty AT bnl.gov> 
Sent: Friday, June 14, 2019 2:34 PM
To: BNL Mail <kistenev AT bnl.gov>; Lajoie, John G [PHYSA] <lajoie AT iastate.edu>; 
EdwardOBrien <eobrien AT bnl.gov>; Xiaochun He <xhe AT gsu.edu>; Richard Ruggiero 
<ruggiero AT bnl.gov>; Stefan Bathe <bathe AT bnl.gov>
Cc: sphenix-hcal-l AT lists.bnl.gov
Subject: Re: [Sphenix-hcal-l] summary from production readiness meeting at 
Uniplast

Much as I hate to agree with Edward, I think we should at least consider and 
document the alternatives so we do it with clear eyes looking forward and 
aft.  Even if the decision really is made for contractual and schedule 
reasons which can't be changed now, we should collect the drawings and any 
test results that exist in one place, and ask Carter to drill a sector so we 
know how hard it is (in two ways).  And sometimes in discussion someone 
points out other ramifications of the decision.

Is the next HCAL meeting too late or too soon to get this done and tell 
Uniplast?

On 6/13/19 3:52 PM, BNL Mail wrote:
> John, Maybe we need to take few days make a step back and discuss this 
> issue instead of stating that decision is already made. I happened to 
> know that original pattern was developed not for no reasons- we tried 
> to create fiber configuration symmetrical with respect to the central 
> long axis in the tile in the hope to keep it as uniform as possible. 
> This was made and this is still preserved everywhere except redesigned 
> tile 25 (5). When I agreed to this modification I was left with 
> impression that interference is between tile and comb which really 
> exclude any chance for original design to stay. If Stefan and others 
> do believe that relatively small extra work may result in returning to 
> what we initially designed I will support this path wholeheartedly.
> It will make calorimeter a little better and will save all good work 
> made at Uniplast and will keep our reserves of consumables (fibers, 
> wrapping etc) untouched (will help IHCal) and in the end it will save money.
> Edward
> 
> Sent from my iPhone
> 
> On 13 Jun 2019, at 19:31, Lajoie, John G [PHYSA] <lajoie AT iastate.edu 
> <mailto:lajoie AT iastate.edu>> wrote:
> 
>> Hi Stefan,
>>
>> The overall decision is made. I appreciate everyone trying to be 
>> creative, but there is no need to spend tech time and modify all the 
>> steel sectors to accommodate a mistake in the scintillators that is 
>> more easily remedied by having Uniplast make what we actually ordered.
>> I don’t see a compelling need – we have ample time to make the 
>> pre-production sectors.
>>
>> We could consider modifying ONE sector as you described, which would 
>> allow us to get a start assembling one sector with the old B25 tiles 
>> if necessary, but we would replace it with the correct B25 tiles once 
>> they arrived. I’m still not sure that is worth the effort as we could 
>> still learn a lot by partially assembling a half-sector up to B25 and 
>> testing it.
>>
>> Regards,
>> John
>>
>> *From:*Stefan Bathe <bathe AT bnl.gov <mailto:bathe AT bnl.gov>>
>> *Sent:* Thursday, June 13, 2019 7:20 PM
>> *To:* Lajoie, John G [PHYSA] <lajoie AT iastate.edu 
>> <mailto:lajoie AT iastate.edu>>
>> *Cc:* sphenix-hcal-l AT lists.bnl.gov 
>> <mailto:sphenix-hcal-l AT lists.bnl.gov>
>> *Subject:* Re: [Sphenix-hcal-l] summary from production readiness 
>> meeting at Uniplast
>>
>> Hi John,
>>
>> There is an alternative to replacing the B25 tiles:  tap ten 
>> additional holes per sector to accommodate the tile clips for the B25 
>> tiles we have on hand.  Richie, Carter, Aron, and I just discussed 
>> this.  We’d make a jig to make the drilling and tapping easier, and 
>> then it would take about two days of tech labor to tap the 60 holes 
>> for the six preproduction sectors.
>>
>> The obvious advantage of this option is that we wouldn’t have to rely 
>> on the replacement tiles to get here in time.
>>
>> We should make a decision which way we want to go.
>>
>> Regards,
>>
>> Stefan
>>
>> --
>>
>> ---------------------------------------------------------------------
>> ------------
>> Stefan Bathe
>>
>> Professor of Physics
>> Baruch College, CUNY
>>
>> Baruch:                                     BNL:
>> 17 Lexington Ave                      Bldg. 510 office 940                 
>>                  
>> office 2-229 phone 646-660-6272                phone 631-344-8490
>> ---------------------------------------------------------------------
>> -------------
>>
>>
>>
>>     On Jun 13, 2019, at 11:43 AM, Lajoie, John G [PHYSA]
>>     <lajoie AT iastate.edu <mailto:lajoie AT iastate.edu>> wrote:
>>
>>     Dear HCAL’ers:
>>
>>     Xiaochun, Anthony, Edward toured Uniplast Wednesday and met with
>>     Victor Majatski to discuss the results from the pre-production and
>>     action items for the full HCAL tile production. The notes from
>>     this meeting are attached for reference.
>>
>>     Something not listed in the notes is that for the pre-production
>>     tile B25 was manufactured to an older design, before the light
>>     guide was moved to accommodate the combs in the outer HCAL.  This
>>     happened because an operator was on vacation when the production
>>     switch was made to B25, and the wrong file was loaded into the CnC
>>     machine. Uniplast recognizes this mistake and will replace the B25
>>     tiles – they have sufficient spare materials on hand to start
>>     immediately and expect to have the replacement tiles completed in
>>     two weeks. Ideally we will still get them in July for the sector
>>     assembly, and I have spoken with Anthony about fast-tracking
>>     testing.  We have reviewed the rest of the tile designs and they
>>     are OK; Megan plans a test fit of a complete set in an oHCAL gap
>>     soon to verify.
>>
>>     Nobody wants things like to happen, but they do. If everything
>>     seemed perfect I would worry what we missed….
>>
>>     Regards,
>>
>>     John
>>
>>     *
>>     John Lajoie*
>>
>>     Professor of Physics
>>
>>     Iowa State University
>>
>>     (515) 294-6952
>>
>>     lajoie AT iastate.edu <mailto:lajoie AT iastate.edu>
>>
>>     <Summary of HCAL Scintillating Tile Production Readiness
>>     Meeting.pdf>_______________________________________________
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--
John Haggerty
email: haggerty AT bnl.gov
cell: 631 741 3358