Jennie W, Jeff K, Josh F, TJ S,
Summary: SPI interferometers aligned, shroud installed successfully. One stray beam and possible clipping on shroud to investigate/deal with but otherwise all problems were solved. Obligatory success photo taken by Josh.
Today we:
- reseated the M_M5 mount in its holder. We had troubles with this stick-slipping when we tried to move it. Jeff replaced the 45 deg adaptor part D2400336-v4 S/N 001 type 1 with S/N 002. This seats better in the holder.
- realigned beam to QPD A and B using picomotors M_C1 and M_M1.
- Confirmed other two picomotors M_B4 and M_M2 work and their pitch DOF (in breadboard basis) matches left/right on picomotor controls.
- We had some weirdness in the meas IFO which Josh has solved and will discuss in other alog from Josh (LHO alog #90680).
- During this debugging we used the oscilloscope to plug into analog outputs for meas and ref IFO and a commercial RF source.
- We used the breadboard steering mirrors to get 85.9 % heterodyne efficiency on the reference IFO PD A and 88.9% efficiency on reference IFO B.
- With no adjustment the measurement interferometer PD A had 86% efficiency and PD B had 93.4% efficiency so we will take this (ch4 on scope is PD A, ch2 is PD B).
- This afternoon we installed the shroud around the ISIK breadboard.
- We had to move the fiber spools to avoid the bottom shroud bracket and these are now close to the edge of the beam tube where it meets HAM3 in the -x direction.
- After installing the shroud panels both QPDs had dropped in power by ~2V, will investigate on Monday as the beam does not appear to clip the shroud when we check with the card.
- There is also a stray beam from the FBR_PWRIN_REF PD that hits the upper shroud stand-off on the lower panel on the -y side and then hits the door cover, this will need dumped somehow.
- After moving the fiber spools I checked the FBR PWRIN channel for meas and ref and these both drifted after we rerouted the fibre spools but the level seems to have been dirfting more than this since we got into chamber this afternoon at 14:20. The first cursor in the photo is when we started moving the spools and the second is when I shuttered the laser.
More details regarding the baffle installation:
When placing the below table baffle brackets, there was a ballast mass baffle (D1700262) that was blocking the angle bracket for the furthest -Y bracket. The bracket could not slide under the ballast mass baffle (bmb), so we decided to move the bmb in the +Y direction a few inches and I had to loosen the baffle panel within the feet to slide it up a few mm and then reclamp. This allowed the bracket to slide under the baffle just to the side of the feet, but the move partially exposed a corner of the shiny ballast mass stack.
The lower baffle shroud that covers the breadboard needed the fiber spools to be moved. We moved them over one set of bolt holes, but they are quite close to chamber edge, I'd guess around 1/2". Jeff then centered the two aperatures to the SPI beam, and we called it good. We still need to B&K the whole area.
Just did an 8 hour trend of the fiber power monitor channels for REF and MEAS channels (left two plots) and the optical lever QPDs (right two plots) to check whether we expect variations on the order of ~2V on the QPDslike we saw on Thursday before and after baffle installation.
From this trend the power appears to drift more than this for two hours after unshuttering the laser (around 15:56 UTC), but once it reaches a steady state both QPDs were only drifting by 1V and the fiber power input monitor PDs by 1V or less.
Conclusion: I think we would have seen a dramatic power drop on Thursday when we installed the shroud, that I would expeact to have been much larger than the trends I saw today.
