sPHENIX HCal discussion

[Rusty Towell <rxt01a AT acu.edu>]

Hello,

I haven’t been following every detail of this work, but I’d be happy to help interface with EJEN if you’d like.  EJEN is just a 40 mile drive from my home and I’ve met several times over the past year with their owner and their chief engineer.  So if you have specific questions about their production process or if you’d like for me to request updated quotes, etc. … I’d be happy to help.  Just let me know.

thanks,

Rusty

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On Jan 6, 2016, at 3:00 PM, Edward Kistenev <kistenev AT bnl.gov> wrote:

Ed, 

I have quotes from EJEN for production of tiles from locally made material (they never told me if it is extruded but the base material is the same polystyrene. I have a quote for all other work (not counting coating - no chemistry) from local Long Island vendor. Prices are known and EJEN tiles are probably flatness/thickness better then Uniplast (based on samples of waveshifting tiles from EJEN I’ve seen). 

Keeping thickness under control is not a problem for Uniplast, as I said it was my mistake ignoring technological changes. In future the measurements like those in Megan tables will become part of the normal production procedure (in fact UNIPLAST is currently doing similar measurements on scintillator plates they have in stock). Each tile will get its passport, we are not going to accept undocumented tiles in future. This rule will be applied first time to production of tiles for the forward direction. There are still couple of unresolved issues with respect to  tile design - we need to change fiber exit design (it MUST have light blocker, it is now proven that hot area around fiber exits which may screw the measurements in the Inner HCal is due to bulk/cladding light) and SiPM coupler - no more screws to drop between still plates. Production will not start before I’ll be able to fully resolve all remaining design and QC issues. 

It is very critical to resolve wrap issue. As much as I like things made on a cheap - wrap as it currently made at Uniplast is not a solution. It must be done differently and if we are making effort to make it technically right, we may also make an effort to make it light-treatment correct. That means - remove Al foil which is specular reflector what kills the purpose of diffuse reflective coating and replace it with teflon. Correctly arranged Tedlar external cover will do the rest - no overlaps except 50mkmm of polyimid tape on one side. 

I am planning to go to Russia as soon as we are through with initial certification of run data (end of May, early June). During my last trip MEPHY (A.Taranenko) was definitely interested in contributing to HCal part of sPHENIX Project and still is.

I am as much interested in success of HCal and sPHENIX as any other physicist in the project. There are number of organizational/production solutions which we may follow if we take steps to secure right material in right quantities early. Example is the scintillator itself. Danger is always in delays, technological and administration   changes etc.

Unfortunately even people are not forever not just machines. 

Edward

Edward Kistenev, PhD

PHENIX Physicist

On Jan 6, 2016, at 5:26 PM, EdwardOBrien <eobrien AT bnl.gov> wrote:

    Hi John, John and Edward,
     I agree that we need to have someone, presumably a
    collaborator from a Russian institution, visit Uniplast
    regularly during all future production, even the next
    prototype round.

    Can someone answer whether Uniplast can correct the thickness
    problems prior to completing the the high eta tile production?

    We should spend some effort to qualify a second tile vendor. Is
    there any chance that we can do this in time for the Inner HCal
prototype
    to be used in April? If not then I suggest we use a second vendor
for a part
    of the high eta tiles, both Inner and Outer. Since we have ordered
the full high eta tile
    complement from Uniplast, the tiles from a second vendor will result
    in us having spares in the end. We are already pursuing
    different production options for the EMCal towers, and will also
    look at a variety of vendors for the Outer HCal steel and Inner
    HCal stainless steel. We should do the same for the tiles.

    Ed

On 1/6/2016 11:12 AM, John Haggerty wrote:

As I said, I'll summarize my e-conversation with Edward about the tile
thickness.  I forgot that to make these tiles, they had to make some
changes to their extruder in order to make wide enough tiles.

picture gets a bit cleaner with UNIPLAST. In summary - this is my fault, I was too certain that 2013 production is a good predictor for what we’ll get in 2015. Ignored the fact that UNIPLAST essentially crossed the line - they switched from 19cm wide band extrusion to 25cm wide extrusion. Lot of hardware modifications and no other consumers except us.
- large tiles are relatively uniform but with excess thickness of ~0.4mm. 0.2 mm are due to coating (I expected 0.1mm or 0.05mm per layer), 0.2mm is due to excess thickness at the edges (temperature regime which is undercompensated by the slit shape);
- small tiles are from tune-up cycles - wide bands but small loads;
- not much care of wrap quality on short tiles (large one were made after my visit - wrap quality was probably improved but sill not strictly enforced.

There is no problem to bring tiles to the spec (we need to decide if we want 7mm or 7.2mm (coated) thickness.
We will also need to decide on wrapping materials - they will set the final tile thickness.
PS. If any measurements on tiles are still going - please add the corner to corner dimensions at the inner and at the outer edges of the tile (cylinder radii) in finished state.

So I would say the lesson is that we probably have to have someone at
Uniplast at least periodically during fabrication who can assess the
production before we ship them to BNL or wherever we decide to send them
first.  We also need to finalize the wrapping, Edward is still
interested in Tedlar, although I think we'll have to assess the
thickness that we'll end up with before we buy a lot of it.

There will be more on measurements later today, I think, from Kenny by
way of Abhisek and Megan that will help us understand how to proceed.

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