Reports until 02:05, Wednesday 29 July 2015
H1 SUS
matthew.evans@LIGO.ORG - posted 02:05, Wednesday 29 July 2015 - last comment - 09:08, Wednesday 29 July 2015(20018)
Excited BS modes

Occasionally, we ring up the BS butterfly mode (2.5kHz), the BS violins (300 Hz) and something at 41Hz.  What is that thing at 41Hz (which is always present, though usually not so big), and how are we exciting the other BS modes?

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matthew.evans@LIGO.ORG - 02:29, Wednesday 29 July 2015 (20021)
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Is the line at 75Hz from the ring heater fans, as in LLO?

jeffrey.kissel@LIGO.ORG - 08:19, Wednesday 29 July 2015 (20028)
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The highest Roll mode of the HSTS is modeled to be at 40.3 [Hz] -- I suspect SR2 or SRM as you drive it for lock acquisition, or they could have been rung up during the low-frequency sawtooth waves from the earth we saw last night.
gabriele.vajente@LIGO.ORG - 09:08, Wednesday 29 July 2015 (20031)
Link

At 75 Hz there is coherence with magnetometers and microphones at the Y end. So I guess it's the ring heater.