sPHENIX HCal discussion

[Megan Connors <meganEconnors AT gmail.com>]

Hi Edward,

I agree that much of the extra thickness especially in the inner tiles is from the wrapping. However, I'm not sure how to best quantify the effect of the compression on the thickness or what that really tells us. Keep in mind that the thickness is not very uniform. I will point out that by slightly prying open the slots on the inner HCal steel skeleton (3 plates are in place) which should only be 8.5mm wide, we were able to slide in tiles that measured over 9mm thick. This obviously puts pressure on the tile but as John said, I think the effects of such pressure should be studied as a function of time. We should also study the effect of the increased pressure experienced by the more thickly wrapped spots on the tiles which may be evident after the April test beam. I think the goal now is to figure out the best way to configure the thicker and less thick tiles for the prototype. Abhisek and I are continuing to take cosmics best we can to have data on all the tiles before any potential compression so we can move forward to the assembly stage.

Best,

-Megan

On Wed, Jan 6, 2016 at 3:25 PM, Edward Kistenev <kistenev AT bnl.gov> wrote:

Hi, Megan, There is something else what would be nice to know. I read your measurements of maximum thickness as the measurements without compression. It is very simple to make a simple three posts jig with one fixed and one vertically movable plates and measure what will happen to that maximum under pressure. If as I suspect it is mainly clobbered cling-tape it may give up enough for most of tiles to be safely loaded into calorimeter at a time when it is assembled.

Edward

Edward Kistenev, PhD

PHENIX Physicist

On Jan 6, 2016, at 5:14 PM, Megan Connors <meganEconnors AT gmail.com> wrote:

Hi John, all,

Attached are two plots summarizing the current status of the thickness measurements. For the inner tiles 69 out of 80 tiles have been measured. I've only seen measurements for 20 of the outer tiles so far. Thickness on the inner tiles is measured at 9 points and the outer at 13 spots as illustrated in the attached images. The plots show the Max thickness measured on each tile in red and the average thickness of each tile in blue.

Best,

-Megan

On Wed, Jan 6, 2016 at 11:12 AM, John Haggerty <haggerty AT bnl.gov> 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.

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