[Aidan, Camilla, TJ]
We returned to the ETMX to work on the HWS this afternoon. We adjusted the positions of lenses 2 and 3 and the HWS itself to better match the nominal/design layout.
Aside from this, it is obvious from an inspection of mirrors and the HWS return beam that there is a LOT OF DUST on all the optics. Also, the HWS beam wanders on the camera by small amounts - I can put my finger on the picomotor mount and see signifcant movement of the beam. The high spatial frequencoes in the return beam (from diffraction from dust) coupled with the beam motion will create significant noise.
We need to clean the optics.
TJ and Camilla did clean the bottom periscope mirror (pictures to follow) but there are still more optics to clean.
For reference, we have seen mottled beams from dirty mirrors before: https://alog.ligo-la.caltech.edu/aLOG/index.php?callRep=27041