Propose design changes on the diffuser unit

Reason for the change:-

See Marco Apollonion’s write up to the Technical Board on 7th of Aug. 2008:-

Hi Andy here comes a ppt sketch illustrating the change from the present configuration (left) to the new one (right) In a summary, the 1cm thick lid will become a ring clamping a plastic (possibly Kevlar) disc. The black dots represent the o-rings used to ensure helium tightness. Wing will send a proper engineriing version of this scribble, he reckons 4 weeks are needed to complete this part.  Marco 

…. together with the cartoon on the next page

Existing arrangement on the cylinder end

10mm thick Aluminium end plate

A reminder of what it looks like now …

Proposed re-design:-

1) Cut out a hole of 240mm diameter on the existing cylinder end plate

2) Drill and tap 24 off M4 holes to 7mm deep.

3) Machine a seal groove of 1.5 x 1mm

B

B

View “B-B”

A

AView “A-A”

Proposed re-design:-

1) Cut out a hole of 240mm diameter on the existing cylinder end plate

2) Drill and tap 24 off M4 holes to 7mm deep.

3) Machine a seal groove of 1.5 x 1mm

4) Bolt a 1.5mm thick plastic plate together with the Kevlar fabric, both of 275mm dia., to the cut-out aluminium end-plate via 24 x M4 bolts. Sealing between the plastic plate and the aluminium end plate is via a 1.5mm dia. O-ring seal.

Safety net made of Kevlar fabric (for impact stopper)

Remarks:-

The proposed design does not infringe on the space enveloped agreed between the diffuser and the tracker fibre route;

A circle diameter of 240mm clear of any metal is created for the beam path as a result;

At the request of Marco Apollonio, a safety net made of Kevlar is needed to stop any flying object hitting the fibre tracker.

It is not know who provides this net (Oxford has no experience with handling and cutting this material). However, the design allows such net to be bolted onto the cylinder end when it is available.

It is estimated that design and workshop time takes approx. 4 weeks to complete as it requires dismantling the presently assembled diffuser unit, machining the new features, re-assembling the unit and re-testing the assembly.