( Aidan, Thomas, Elli)  Recently Aidan noticed fringes on the beam spot on the HWS down at EY.  He also noticed a coupling between beam movement and the spherical power the HWS senses.

In an attempt to clean up the fringes, yesterday I replaced the polarizzing beam splitter which sits just upstream of the HWS with a mirror.  This reduced the fringes on the HWS, improving the image quality.

This morning between 14:14 and 14:30 UTC Thomas and I gave a periodic excitation of PZT_1 and _2 in pitch and yaw and measured the spherical power fluctuation.  We missaligned the ITM to ensure the cavity was unlocked while taking measurements.  It appears we have reduced the coupling between beam motion and spherical power fluctuations.