Last night I aligned the incident beam axis and the Yarm by touching the PZT mirrors and the suspensions.
I didn't estimate how good they were aligned, but I guess the Y arm is now ready for the Y green light.
Next : Y green alignment and the MC spots measurement / alignment.
++ Motivation ++
Prior to the coming vent we want to have the Y arm, incident beam axis and Y green light aligned so that we can align some necessary optics in the chamber.
Also alignment of the incident beam will allow us to re-position the incident beam alignment monitor (i.e. IPPOS and IPANG).
Our plan was to first align the Y arm using the ASS system and then align the Y green light to the Y arm.
++ what I failed ++
First I was trying to measure the spot positions on the MC mirrors to make me sure the beam axis has/hasn't changed.
Also I was going to align the MC suspensions to have nice spot position on each suspension using the MCASS system
because this will help us checking the beam clearance in the Faraday and perhaps re-positioning of the Faraday during the coming vent.
But essentially I failed and eventually gave up because MCASS didn't work. It seems that MCASS needs some modifications in the scripts.
Then, to make me feel better I moved on to the Y arm and beam axis alignment.
++ what I did ++
I tried using C1ASS to align the incident beam and suspensions on the Y arm, but it didn't work.
However the drive signals from ASS and its demodulated signals looked fine. Only the feedback did not work correctly.
Every time I enabled the feedback paths, the arm just lost the lock. Something is wrong in the feedback paths.
Then I started to align the cavity by my hands while looking at the demodulated signal from each LOCKIN module.
I aligned the things until each demodulated signal fluctuates around zero.
At the end the beam spots on the ETMY and ITMY camera looked well-aligned and the transmitted light became larger by a factor of 2ish.