1. Cylinder design
Ian Wilmut 10/11/11

2. Reminders
There are three ideas for structures being considered in the UK
Sandwich cylinders (SCT strips)
Single skin cylinders (old pixel, GVA like it)
Spider web face plates (very conceptual)
We are trying to write an LoI next year, and as part of that some statement is needed to the structure design, locking point design and insertion technique.
Next week at AUW I will give a talk similar to this where I try and inspire a programme to get us to the LoI.
The one key thing we lack to derive a real design is a robust spec. In the absence of this we can investigate but not conclude.

3. What has been done so far
About 18 months ago Stephanie started looking at structures. The initial goals of this work were:
To understand approximate material contributions compared to the stave.
To see if the quality of stave locking could impart significant stiffness from the stave to the cylinder.
This work looked only at single skin cylinders.
The work came to an end when it became evident that:
The locking points are don’t constrain the stave to the cylinder well enough to impart much stiffness to the cylinder
The material contribution of the cylinders is likely to be quite small +11% to +25% more than the populated stave.

4. In more than words…
The focus was on modal not deflection – see next slide
1st 5 modes of 1mm thick cylinder.
F1 = 11.8 Hz
F2 = 46.5 Hz
F3 = 48.1 Hz
F4 = 49.6 Hz
F5 = 51.6 Hz

5. Model studies
Erik Anderson (LBL) is firmly of the opinion that structures should be considered in frequency terms not static ones.
The basis for the argument is that the model study is easier in FEA, and to measure in reality, and that static and modal results can be equivalenced together. For a simply supported beam:
δ = PL3/(3EI)
F = 1/2π (4EI/Lm)0.5
In talking to Erik, Georg understands that this technique is encouraged by Newport (the optical table people), and is the technique used for structural design in both the present pixel detector and the LBL STAR contribution.
If anyone doubts the correctness of this approach we should make efforts to convince ourselves of the validity

6. Plans to move forward
A few weeks ago several of us met at Oxford and discussed structure work – two documents were written and are attached to indico.
They outline the following approach.
Work in frequency space
For 2 initial designs vary all design parameters to find sensitivity to change
Thin wall structure
Sandwich structure
Assume the stave provides no structural contribution
Once there is an indication of appropriate structure explore number of locking points to match stave modes to cylinder modes i.e. don’t make the stave significantly softer or stiffer than cylinder.

7. Alternatives Spider web concept model has been built
It will now be used to verify performance predictions for such a system
If it does behave as expected a complete design will be developed that could be used in place of cylinder.
A very rough CAD model was done for the whole system a few years ago at RAL.

8. Locking points Just a quick update on locking…
Prototype lock point has been passed around on several occasions.
Oxford is making mould for locking points for further prototypes
A sector prototype will be built using these, the interlinks are undergoing more development before this is possible.
On Tuesday Fred, Stephanie, John Hill and Tim met at RAL and discussed detail of insertion further, John will discuss this further in integration update – needless to say the challenges are closely linked to structures and locking

9. Locking Images
Locking point and rails in situ – rails are shown rolling into place
Machined prototype locking point
Rails shown
With two lock points.
Sector design

10. Conclusion Lots has been done, but there is clearly a lot more to do.
Areas being actively pursued:
Spider web face plates
Locking points
Insertion
Interlinks
Areas that have a plan but little work is happening at the moment
Structure design
Structure Spec
For the LoI we need a proposal of what the structures will look like – we are a good way from that yet.
Contributions in this area are welcome