Hang, Danny, TVo, Georgia

Today we worked on trying to improve the simple michelson contrast defect by positioning the CO2 lasers on the ITMs. This TCS work is ongoing and will continue tomorrow.

We can steer the beam using the periscope top mirrors. The diagnostic tools we have are the AS photodiodes (AS_A and AS_B), the shape of the beam on the ASAIR camera, and the HWS contour plots. This is an arduous task due to the long time constant of heating, and confusing results while steering the picomotors, at one point the contrast defect looked very good but we struggled to get back to that same position.

Attachment 1 shows the power on AS_A, and picomotor relative positions (not neccessarily an accurate measure of position), over the course of the evening. We looked mostly on ITMY, amd looked first at yaw and then at pitch. We take these measurements in the MICH_DARK_ALIGN state of ALIGN_IFO, and adjust the offset on the ASC MICH loop to keep the dark port dark. The lowest value we saw on AS_A was ~27 counts, but we swept through it early and couldn't repeat it.

Attachments 2 and 3 are HWS images of ITMY before and after picoing (the after pico-ing might be a bit washed out as it won't be at thermal equilibrium). We're aiming to overlap the CO2 beam with the IFO beam, pictured here.

I noticed both CO2 powers were drifted by ~10 mW over the course of the day, shown in attachment 2, that might not be a problem normally, but might have contributed to us not being able to get back to optimally dark dark port?

Final attachment shows the AS_AIR camera at the end of the day. I misaligned SR2 to get this image but put it back at the end of the day.

Tonight I'll run two scripts to change the CO2 laser power overnight I was going to leave the IFO in MICH_DARK LOCKED but am now having trouble acquiring. I will leave it trying to acquire.