Alexa, Gabrielle, Kiwamu, Sheila
This morning we moved PRMI to the 3F sensors, we used a gain of 3 in the input matrix to move PRCL from REFL 9 I to REFL 27 I, and a gain of 15 to move MICH from REFL 45 Q to REFL 135 Q. This was locked from about 22:26:55 UTC (september 22) to 22:33:20.
We then tried to move on to DRMI but have struggled most of the day to get it locked. We locked it a few times this morning, (21:00 UTC) but haven't been able to recently.
Also, as is typical recently, the anthropogenic noise is higer durring the evenings than durring the day, there must be an evening shift of hanford work. Screen shot of the last week is attached. This pattern started in mid august and has been true since then.
After Sheila left, Jeff and I saw the DRMI locked for a minute or so at around 6:06 UTC. However, after this lock, the DRMI never caught a fringe again.
The settings at that point were:
- MICH gain = 0.5
- PRCL gain = 2.8
- SRCL gain = -20
Also, I experimentally had an off diagonal element of -1 in the REFL_A_RF9_I to SRCL element together with the usual REFL_A_RF45_I to SRCL element at that point. Since there was a 3 Hz oscillation in MICH when it was locked, I increased the MICH gain by a factor of three, but this did not help at all.
I did a quick comparison between the 'evening' (high BLRMS between 1 and 3 Hz as Sheila mentioned) and the 'night' (quiet time).
By looking at the ground, we do see some amplification in the spectrum around ~2.5Hz by almost a factor of 10. However, there is not a lot of power at those frequencies and this amplification doesn't seem to affect the optical lever motion (I looked at PR3).
I'll do a further analysis tomorrow and see what SUS and SEI are doing, but I wouldn't bet this is your issue so far.
I also don't think this is the reason we have not been locking DRMI, since th situation was similar on the nights we did lock, and the fringe speed is 1-2 fringes per second. It is just interesting that we are actually louder at night than durring the day.