corey.gray@LIGO.ORG - posted 02:13, Thursday 12 December 2019 - last comment - 08:16, Thursday 12 December 2019(53856)
New DARM Noise Tonight
During our handoff tonight, Cheryl mentioned possible DARM noise on the DARM BLRMS ndscope for mainly the 20-34Hz band. One can certainly see noise on our running DARM spectra in the front of the room where a certain region gets noisy ever few seconds (but it can also be quiet up to a half to full minute, too.) It's subtle because we do not see the range dropping noticeably. Below are a couple of examples of the noise:
- First two plots is the DARM during a couple of these noise bursts (blue is spectrum from 2-days ago & red is tonight).
- Additionally, on Omicron you can clearly see this new noise in this current lock and also see it getting worse as we go (attached is a side by side comparison of omicron from Dec9th & tonight).
Will continue investigating, and tagging DetChar for assistance.
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The noise Corey is seeing here are scattered light shelves pushing in to the spectrum because the microseism ground velocity is pretty high (for LHO). See attached BLRMS of the 0.1 to 0.3 Hz band. Gabriele's got a good aLOG modelling the effect in LHO aLOG 47417 -- though the scattered light source in his aLOG is not what's going on here; that particular source has been mitigated. Unclear what the particular source is, but my impressions come from Robert -- whom may have an aLOG pending...)
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