mark.barton - 23:18 Monday 13 June 2016 (1830)
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BS Flag/Prism Gluing Results
With Tatsumi-san, Fabian.
We went to Kashiwa to see the result of the dummy BS gluing. Unfortunately there were multiple issues:
The LL (lower left) flag came off as Fabian removed it (the fixture didn't come away easily and he might also have been a bit rough).
The LR flag fixture came off easily and the flag stayed on.
The UR flag fixture came off with considerable resistance - it needed levering. Flag stayed on, but was wobbly - adhesion was obviously only partial.
The UL flag fixture came off easily but flag was obviously already broken.
Both sapphire prisms had insufficient glue. The right one was straight and just had patchy glue coverage. The left one was leaned back so there was a large gap at the top (sufficient to insert a thin sheet of plastic film several mm) and most of the glue had pooled at the bottom. It probably can't be used even for the test hang because with force from the wires it will tend to cantilever and crack.
The metal prisms were superficially OK and resisted moderate force, but there was no glue visible around the edges, so a bit more would probably have been good.
We take two lessons from this:
(i) We need to apply a _lot_ more glue, especially to the face of the dummy BS which has lots of fine grooves that have been left behind from machining and which soak up a lot of glue.
(ii) We need to improve our technique in using the micrometer fixtures for applying the prisms. (The procedure calls for the alignment of the prisms to be checked before the glue is applied, and we did this, but we'll need to do it more carefully, possibly with a magnifying glass.)
Because so much rework was obviously going to be required, we broke the remaining flags off. The UR flag almost fell off, but the LR one put up a reasonable resistance.
Hirose-san has offered to organize to get the sapphire prisms removed with acetone.
Photos of this and other BS Test Hang stuff are at https://goo.gl/photos/tVGoebw7FTRMAYB2A .