[Moller_intdet] [EXTERNAL] Detector mounting structure

[Michael Gericke]

Hello everyone,

I am attaching my conceptual design for the detector mounting structure.
Since we haven't had anything of this sort ready for getting meaningful
cost estimates (and I had to do this for the CFI quotes anyway), I decided
to make a design that could be submitted to a company for a quote request.
I am still waiting for them to get back to me.

The attached pdf is CAD generated and you can zoom in and rotate the
models. If you wish to have the CAD files, I'll be happy to upload them
somewhere. The attached movie illustrates how the individual modules
can be assembled (sorry, the files are fairly large, so one has to be 
patient).

A few points I want to make:

1) As I said, this is a conceptual design and I am pretty sure it can be 
optimized.
     I tried to balance mounting rigidity with as small a material 
budget as possible,
     but I am sure one can further improve on that. Maybe it will 
provide some food
     for thought for the group working on the structure design.

2) Some of the parts are complicated; The company I spoke to said that 
they could
     either 3D print or use a 5 axis CNC to make the more complicated 
parts, but I expect
     the cost to be higher than what we budgeted up to now, especially 
if we decided that
     we want to us a carbon fiber based material, rather than aluminum.

3) I think I know how one could simplify the complicated parts and make 
it cheaper, but at
     the cost of less rigidity, I think.

4) This design treats the PMT-LG-Quartz assembly as a unit, which will 
make light tight sealing
     easier. The mounting plates for each module would allow using 
washers to adjust angles, if
     need be.

5) The extra space needed by the "skeleton" for each module causes the 
rings to be spread out
     a little more, in the beam direction. One can play around with the 
structure to squeeze that
     together, but I would caution against overdoing that, as it could 
get impossible to assemble
     and service parts. It would be better to adjust quartz tile size 
and mounting radii.

6) I think we will need two separate, concentric cylindrical structures, 
one that will hold the
     modules, as in this design, and a separate one that will hold the 
shielding. I don't think we
     can afford to have a high weight load on the module structure, as 
it was suggested in the
     previous designs.

7) We will need to think about whether we need to flush the light guide 
with dry air, to prevent
     possible reflectivity degradation, which would further complicate 
the design. The modules would
     support a light and air-tight bag around each one and one could 
imagine feeding the air through
     the PMT housing.

So, while this still just a preliminary design, I think it can serve as 
a first basis for a real cost
estimate of the mounting structure and will show the CDR committee that 
we have at least
thought about the mounting details.

As soon as I have a quote for the module parts, I will pass it on to Carl.

Cheers,

Michael




-- 
--
Michael Gericke (Ph.D., Professor)

Physics and Astronomy
University of Manitoba
30A Sifton Road, 213 Allen Bldg.
Winnipeg, MB R3T 2N2, Canada

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