There's been a lot of wondering about the CO2 alignment relative to the center of the optic so we decided yesterday afternoon we decided to step down the CO2 X/Y and look at the centering, and then overnight we stepped down the Ring heaters on both X and Y. Attached are the contour plots showing that the centering isn't that different between X and Y, but Jenne pointed out that Y is not as good as X, it's off in yaw and so we can probably do more optimization there. However, this does not capture the effect of miscentering the IFO beam on the test mass which from this ALOG shows that the IFO beam is quite a bit different from the center as well.
I wanted to compare the spot positions according to the Hartmann, for the ring heater (test mass geometric center), CO2 beam, and IFO beams. All of this information is already on the log but I wanted it in one image, see dodgey screenshot of screenshots attached.
It seems like on ITMX the CO2 and ring heater beams are somewhat concentric, but the IFO beam appears ~2cm off in pitch (2 uncalibrated-hartmann-basis cm). I'm not sure how reliable this measurement of the IFO beam centering is: it disagrees with the spot position measurements we did on friday which suggested we are more off center in pitch than in yaw.
On ITMY the CO2 seems better aligned to the IFO beam than the ring heater, but all 3 are slightly different. These miscenterings might contribute to the astigmatism seen with the CO2 lasers are on.
