jess.mciver@LIGO.ORG - posted 16:30, Monday 22 July 2013 - last comment - 16:21, Monday 29 July 2013(7159)
6.8 Hz line found in top stage ITMY BOSEMs traced to stage 2 of the ISI
Daniel Halbe, Jess McIver
Daniel has shown a strong, persistent line at 6.8 Hz in all DOFs of the top stage BOSEMs of the ITMY since at least June 12.
As a follow up to his study, I looked for this line in the ITMY ISI and found it in stage 2: very sharply in RX, strongly in RY, somewhat fainter in Z, and much quieter in X, Y, and RZ.
The line is not seen in any DOF in stage 1, looking at the T240s.
Normalized spectrograms of representative DOFs are attached.
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I have discovered a line very similar to this at Livingston and it occurs at 7 Hz. This line is found in Roll (very strongly) and not as strong in pitch. It appears to only show up in those two degrees of freedom and only in the top SUS mass. It does not show up in the ISIWIT channels or the top stage of the ISI. Also it does not show up in any of the other suspension stages.
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I looked at spectrograms, time series, and ASDs for the CPS sensors on ST2 of the H1 ITMY ISI in all global degrees of freedom, but saw no evidence for a line at 6.8 Hz. An ASD of each CPS DOF during this time is attached in .fig form.
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