While assessing the IMC alignment for SR work, we (Kissel, Kiwamu, me) noticed a significant amount of scattered light from the transmitted part of the PR3 OpLev beam. See photos. It looks to be a bit low of center on PR3 and is scattering off a nice shiny round aluminum piece in the MC REFL periscope directly behind PR3. Looking for advice on what to do about it.
I also noticed that last week when I was up there, and we noticed this at LLO also and unfortunately it seems that all the op lev mirrors appear to transmit some % of HeNe light (I wont go into details as to why), and after much round discussion when we were closing up at LLO (we discussed putting black glass behind every optic) it was decided to just leave as is at LLO. We dont seem to have run into any problems because of it.
Matt is referencing Bug-108.