Keita, Anamaria
Following the work on pick-up on the PZT electronics at LLO, we find that there is coherence between PZT1 MON and DARM at various peaks! And PZT1 MON is so noisy that the noise is larger that the dither peak at 4.1k.
We would like to add toroids to these signals as soon as possible and will carefully check tightening of cables.
We have been discussing the relative merit of a ground isolation process for the OMC similar to that done in the end ESD system. Up-votes for such an activity would bolster our case.
Craig, Anamaria
We looked around at the HAM6 rack, we saw nothing amiss. We turned off the pico driver while we were there.
The OMC PZT signal is coherent with magnetometers, especially the ones in the electronics room (EBAY). This noise dominates all the EBAY magnetometers. We should be able to find the source in there.
The coupling seems to come and go from lock to lock, but the PZT noise has been there since at least O2 (Craig will post a plot).
It would be good if someone could look at the behavior of these peaks (the coherent ones from the main post plot) in DARM over the past few weeks/months.
As Anamaria says, the PZT1 monitor forest of peaks has been there since O2. The noise in PZT1 MON has not changed levels very much, but somehow the coupling is worse now: we see strong coherence with DARM and PZT1 in some locks. We do not understand the nature of the coupling. Today we flipped some switches on the fast shutter chassis to with no changes apparent in the PZT1 noise.
To clarify, there is noise in DARM at approximately 70 Hz harmonics, and they are coherent. I zoom in here on the top 3 coherences around 550, 820 and 1100 Hz. But sometimes there's a bit of coherence as low as 280 Hz.
A second observation is that some of the peaks are visible in the DCPDs when unlocked.
