Sheila, Jenne, Terra, Matt, Lisa More complete entries will follow, but the bottom line is that we are still missing the main source of noise below 200 Hz (above 200 Hz jitter/intensity noise should explain most of the noise we see). We had another long lock today at 50W (broken by a new PI ) and we tried several things: - the reduction of the flow rate done in the PSL this morning didn't really last (see here ), so the PSL table motion is only very very marginally better than it was; - Jenne played more with MICH and SRCL FFs, the subtraction is not perfect, but their contribution is negligible at 100 Hz; - we did AL2, and that reduced a lot the noise below 30 Hz; - we checked that all the actuators were in their nominal low noise state state; the ITMs ESD had the low pass OFF, so we engaged them (no impact on the noise) - the ESDX bias was at zero as expected, all coils where in nominal low noise states; - Jenne lowered the 9 MHz modulation depth (see https://alog.ligo-wa.caltech.edu/aLOG/index.php?callRep=29817), getting rid of the 900 Hz peak; - Sheila did some exploration of POP offset and IMC WFS offset to minimize jitter (to be continued) - OMC alignment to be checked as well; - I believe the calibrators have checked the low frequency calibration, and they are confident that it is not off by more than 20%; - Matt tried to close the ISS with the photodiode in the new location (https://alog.ligo-wa.caltech.edu/aLOG/index.php?callRep=29812), but that didn't work. Data around Sep 20, 6 UTC should be good to look at, close to the best low noise state achieved so far. Bruco, actuator noise estimates, checks of couplings with (new wrt O1) TCS-related electronics, and other suggestions are very welcomed.
TJ, Andy, Josh
Bruco results are here using OMC-DCPD_OUT_DQ as the main channel: https://ldas-jobs.ligo.caltech.edu/~thomas.massinger/bruco_1158386417_OMC_DCPD/
The targeted time was 10 minutes beginning at 6:00 UTC on September 20th.
OMC Null shows up pretty strongly at very low frequencies, maybe there's a slight detuning between the OMC DCPDs?
It looks like most of the noise below 100 Hz is correlated with vertex length control signals (MICH error/control, PR2/PRM/BS drive signals).
Attachment 1 zooms in on the coherence between MICH/PRCL and DARM. Coherence with MICH peaks at around 30 Hz and falls off as it approaches 200 Hz.
From 100 - 200 Hz it looks like the IMC alignment error signals start to show up more strongly.
I'll happily rerun with a different target channel if it would be useful.