As a preparation for the upcoming dual arm experiments, I started revisiting the PRMI lock.
PRX and PRY locking:
I started it from PRX as usual. The alignment at the beginning was not terrible: the beam was multiply-bouncing in the power recycling cavity. Aligning PRM immediately gave me good fringes in POP18 and REFLAIR PDs. Note that I assumed that the input pointing had been already good so that I don't have to tweak IM4, PR2 or PR3. Once I got the right LSC settings, it locked reliably as it used to be. I had to set the state definition to be manual for LSC-PD which toggles either only analog or digital sides of the whitening filters. Also I enabled the PR2 and PRM L2P filters because they were not on. I simply put a gain of 1 on them. It didn't seem to do something bad.
I steered BS to get the highest buildup in PRC when I was locking PRY. I had to move the pitch by 7 urad and yaw by 2 urad. Note that they had been originally adjusted for the ALS-Y beam and the alignment sliders had at 190.10 and -268.40 for pitch and yaw respectively before I steered it.
PRMI locking:
BS didn't have the oplev servos running, so I enabled them. All the LSC settings were done by the guardian. I am not sure why it doesn't lock at this moment. I am hoping that tuning the LSC gains will give a smooth lock once we (re-)figure it out. There were several times of short-lock: each of them stayed locked approximately for 1 sec. It looked as if the PRC gain was not big enough. However, increasing the PRC gain did not improve the situation. Hmmmm. I tried different gain settings, but no luck so far.
Some other notes:
Also, I was not sure how well the beam pointing had been adjusted. We may want to revisit the pointing because it can repeatedly lead to unnecessary alignment exercise in PRMI.