andrew.lundgren@LIGO.ORG - posted 08:02, Friday 26 April 2019 - last comment - 18:15, Monday 29 April 2019(48772)
Slowly wandering line from squeezer
A slowly wandering line in h(t) on April 21 between 60 and 120 Hz appears to come from the squeezer. The line was noticed in Edgard Bonilla's DQ shift (wiki link). It appears on at least two other days. It's subtle and hard to notice, but a spectrogram of the bucket captures it (first attachment). Zooming in on an hour, we can match h(t) up with some of the squeezer channels. The second attachment is an hour of h(t). The third is a squeezer channel where this line, and others, are very bright. The highest of the lines also just barely appears in h(t). I don't think this is pickup from DARM because the lines are much more prominent in the squeezer. We haven't yet tried to track where in the squeezer these might originate; I wanted to just quickly document that this is happening.
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Did you get a chance to check the accelerometers on the tables (ISCT6 and SQZT6 - sensor maps at PEM.LIGO.ORG)?
The wandering squeezer line seems stronger today (26 April) (see Fig. 1). The next two images are the same as Andy's above but for today. Note how strong the lines are in the SQZ channel. The final two figures are the accelerometers suggested by Robert.
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I don't see anything in the squeezer or ISCT6 accelerometer over the time in these plots.
Strong wandering lines seen today (29th April) too. They stay in DARM for intervals of ~30 - 60 min. I see the same trends as described before - the wandering line appears in H1:SQZ-OMC_TRANS_RF3_Q_NORM, but not in any of the accelerometer channels. I attach a pdf with some spectrograms.
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