Aidan. Alastair.

Around 10:40AM Alastair and I were looking at the ITMX HWS EPICS channels (spherical power, prism, etc) and noticed them getting very noisy. After some discussion with people in the control room, it turned out that there were some white noise injections going into the ETMX suspension.

We started streaming the image from the HWSX camera to the control room - it's peak intensity was around 1500 counts. We misaligned ITMX by several hundred micro-radians, until the return probe beam disappeared from the HWSX stream. There was a residual beam in the image, with a peak intensity of around 300 counts, that was swinging around. We confirmed this was ETMX by changing the pitch of ETMX from 403 to 360 micro-radians and observing the residual beam disappear.

Once the IFO alignment is settled, we will likely need to adjust the HWS alignment so we don't get any return beams from the ETMs.