Danny TVo Georgia
Today we decided to be more scientific about decoupling the CO2 misalignment and Michelson mode mismatch parts of the contrast defect. We turned both CO2 lasers off and waited for them to cool down (leaving the ring heaters on). The first attachment shows the AS Air camera returning to a bullseye mode. From the rates of cooling and the image on AS_AIR, we suspected that CO2X is misaligned predominantly in yaw, and CO2Y a bit in pitch. This is confirmed when we plot the contours as we cooled down and compare them to the IFO, shown in attachments 2 and 3 for ITMX and ITMY respectively. We've now turned CO2X back on, and once it heats up we will pico and look at AS_C until we return to the bullseye mode. We will then turn on CO2Y and (either today or tomorrow, it takes a couple of hours to reach thermal equilibrium) finalise its alignment in the same way. Then the only degree of freedom left to optimise the contrast defect is the CO2 laser power.
We tried to pico CO2X while looking at the HWS and the AS port with only CO2X on. We moved by -2000 counts but saw no change on the Hartmann or the AS camera (we were dominated by bullseye mode with only one CO2 laser on though). Might be good to repeat this test at a lower CO2X power, and maybe check that this picomotor is actually working.
We turned on CO2Y, according the HWS spherical power it's still reaching thermal equilibrium, the AS_AIR camera looks like it's dominated by 20 mode, if we still believe the HWS from before maybe the first thing to try tomorrow is correcting for horizontal misalignment by pico-ing CO2X and vertical with CO2Y, but I'm not really sure. Could also turn CO2X off and look only at CO2Y but again I think the bullseye will dominate.
There seems to be clipping in ITMY CO2 which was not there before, this is strange but could be the source of our asymmetric heating.
