sPHENIX HCal discussion

[Stefan Bathe <bathe AT bnl.gov>]

Dear All,

I’m not trying to argue with the decision to wait for the correct B25 tiles 
here.  I’m fine with that.  All I’m trying to do is describe the issue in 
words so everybody understands what we are talking about.  Maybe Richie can 
add a picture to illustrate my words.
1) Description of geometry:
- Tile clips are fixed to the absorber plates with screws.  The clips serve 
two purposes: (i) hold the tiles in place and (ii) hold the preamp boards.
- Each clip holds two tiles (in each sector there are five clips in the phi 
direction (for the ten tiles in the two towers) times 24 in eta).
- The clips are screwed to the tiles by a hole in the light blocker.
2) The problem:
- In the original design of tile B25, the preamp board collides with a comb.
- In the current design, the tile clip was moved away from the comb.  This 
goes in hand with a changed position for both the light blocker in the tile 
and the hole in the absorber plate.
- We cannot install the original-design B25 tiles without modification of the 
absorber plates since there is no longer a corresponding hole in the absorber 
plate to hold the clip.
3) The solution:
- produce B25 tiles according to current design and install
- fall-back solution:
   - drill and tap holes into absorber plates at position of original design 
(there are 20 B25 tiles per sector, each clip holds two tiles, so this is ten 
holes per sector)
   - to avoid collision of preamp boards with combs, place additional clips 
at position of current design for the sole purpose of holding preamp boards  
(hole in absorber plate already there)
(this solution of moving only the preamp boards out of the way with 
additional clips was also implemented for B21 tiles; but there the holes in 
the absorber steel at the position of the light blockers are still there 
since the tile design was not changed)

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 14, 2019, at 7:34 AM, John Haggerty <haggerty AT bnl.gov> wrote:
> 
> 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>_______________________________________________
>>>    sPHENIX-HCal-l mailing list
>>>    sPHENIX-HCal-l AT lists.bnl.gov <mailto:sPHENIX-HCal-l AT lists.bnl.gov>
>>>    https://lists.bnl.gov/mailman/listinfo/sphenix-hcal-l
>>> 
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> 
> 
> -- 
> John Haggerty
> email: haggerty AT bnl.gov
> cell: 631 741 3358