We were locked at 24 Watts for just over 2 hours before we rang up a PI that shows up in the Y arm QPDs at 15734 Hz. I increased the ring heater power (for both arms )from 0.5 to 0.6 Watts. template with the QPD IOP channels is attached. I tried to reduce the power, but we lost lock when I did that perhaps because the ISS second loop was on. The lockloss was at about 3:00 UTC on July 17
We suspect this was not PI, that it was the roll mode.
It would be useful if someone could track down which optic this was by looking at the roll mode peak RMS trends and looking to see if it in fact did saturate any of the actuators.
Rana
ETMX ring heater has asymmetrical heating at the moment (0.5W upper ring 0.6W lower ring). Not sure if you'd like to keep the setting so I'm leaving it there....
Matt, Sheila
Matt looked at this lock this morning, and saw that although the ROLL mode might have increased in the last few minutes it likely wasn't the culprit. However, there was a line at 1055 Hz that apeared and grew in the last 20 minutes of the lock, shown in the attached screenshot. This would indicate that the PI could be at 15329 or 17439, so this is a new PI for us. (past incidents alog 17903 and alog 18965) As far as I know this is also a different frequency from what has been seen at LLO.
Unfortunately, in my hurry to grab some fast channels for the QPDs, I used the LLO channel names but we are uusing a different ADC, so I got the wrong channels. So we don't really know which arm this was in.
I've made a template that anyone who suspects that a PI is rung up can run:
/ligo/home/sheila.dwyer/ParametricInstabilities/PI_IOP_template.xml
The assymetry in the ring heater was my mistake.
