Estimates of the jitter contributions to DARM from table vibrations are given in Figure 1 for LHO from last week, and compared to those from LLO from a couple of weeks ago (https://alog.ligo-la.caltech.edu/aLOG/index.php?callRep=41294). LHO is now a lot better than it was in O2. There are 4 peaks at LHO that are greater than 1/10th of the current DARM floor and one that shows in DARM. This is for 25 W - the coupling may get worse with higher power. Compared to LLO, there are 3 peaks in the LHO estimate that are larger than the largest LLO peak. Two of the optic mounts producing the worst peaks have been identified and are pictured in Figure 1 – both have high Qs and should be easy to damp.
Most of the LHO improvement over O2 noise is consistent with the reduction in table motion, demonstrated in Figure 2. We hope that this motion is further reduced with the changes we made this week during the vent. I haven’t been able to check because of the noise from the purge air in HAM1.
Figure 3 has a comparison of table motion at LHO and LLO. The first page shows motion of the periscope and the table at both sites at the time of the BNS in O2. The second page shows current levels. There have been improvements at both sites and LHO has gone from more motion than LLO above 200 Hz, to less motion than LLO now. The third page of Figure 3 shows that, even with water off, LHO is worse than LLO with water on between 30 and 200 Hz. This is roughly the case even when the whole LHO site is off (https://alog.ligo-wa.caltech.edu/aLOG/index.php?callRep=42087).
Text files for LHO DARM contributions from PSL table vibration, columns 1 and 5
LLO: https://ldas-jobs.ligo.caltech.edu/~philippe.nguyen/test/pemcoupling_test/2018f_psljitter_LLO_higherupperlimthresh/CompositeCouplingFunctions/L1:IMC-WFS_A_I_PITYAW_QUADSUM_composite_coupling_data.txt
These sites also have the coupling functions, but I dont include them here because we want to work more on the calibrations.
Robert S., Philippe N., Anamaria E., Terra H.
