I am working on a quick check of vibration sensitivity to make sure there are no major issues. I got some injections done tonight. The worst low frequency coupling spot seemed to be ISCT1 (the beam diverter was reportedly closed), but I didn’t get a chance to inject lines in the 100 Hz region. The interferometer lost lock and, at first wouldn’t lock DRMI, but after aligning BS it got up to “DRMI to POP” and lost lock at that stage several times.
The REFL beam diverter will have been closed, but in O2 we left the POP beam diverter open so we could use the in air POP WFS. Now that our recycling gain is consistently high, I'd like to transition back to using the in vac REFL WFS for the PRC, as we did in O1. This will allow us to close the POP been diverter for the beam that goes to ISCT1, and hopefully eliminate some of this noise.