sPHENIX HCal discussion

[John Haggerty <haggerty AT bnl.gov>]

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.

--
John Haggerty
email: haggerty AT bnl.gov
cell: 631 741 3358