LIGO Document E1300396-x0

DCN- Release aLIGO Pcal Fixed Mirror Seating Bracket

Document #:
Document type:
E - Engineering documents
Bracket needed to force seating of 2" Pcal Periscope mirrors in fixed mounts.
Files in Document:
Notes and Changes:
Note: Rick Savage electronically signed this DCN 5/9/2013. However, his signature was obliterated by the addition of the following notes. 5/10/2013 D. Coyne & C. Torrie reviewed and approved.

1) The drawing has the serial number (SN) stricken out of the drawing note. This is incorrect. Ask the manufacturer to mark the serial number sequentially on each part.

2) This drawing is not linked to its higher level assembly (or sub-assembly), i.e. not linked into its drawing tree. Add this linkage.

3) explanation of the reason for the change:
For the aLIGO Pcals, I designed a fixed mirror mount together with John Wingerd at Siskiyou (D1102439).

Using the PEEK set screws that ISC and others are using to retain 2" mirrors, we have observed significant motion of the mirror when the set screw is tightened.
This appears to be mostly due to the end condition of the set screw, which is quite variable.

We find that oval-point screws perform much better, but still feel that more positive mirror location is needed, especially because we may remove the mirrors for shipment and we want to maintain our pre-alignment. In addition, we want to ensure that the Pcal alignment doesn't creep over time.

We have designed a "Fixed mirror seating bracket" that we would like to release for fabrication immediately. The design seating force is 2 lbs. per arm, 4 lbs. total.

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