Reports until 06:36, Monday 03 April 2017
H1 SUS (SUS)
cheryl.vorvick@LIGO.ORG - posted 06:36, Monday 03 April 2017 - last comment - 08:00, Monday 03 April 2017(35281)
PI mode 23 spiking

in the last 45 minutes PI mode 23 has spiked a number of times - snapshot of the striptool attached

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cheryl.vorvick@LIGO.ORG - 06:58, Monday 03 April 2017 (35282)
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I found this in alog 34787:

"* IMPORTANT: Driving PI mode 23 (for instance when applying damping filters) caused glitchy narrow lines at (14.5, 64.0, 78.5 and 142.5 Hz), this dominated Omicron glitchgram with a 60-80Hz band of high SNR glitches. Commissioners have noticed this an put in place a practice of not damping this mode anymore unless required for lock acquisition."

It looks like mode 23 might be related to the drops in range - see attached plot.

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terra.hardwick@LIGO.ORG - 08:00, Monday 03 April 2017 (35284)
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Ya, as of now do NOT damp this mode. 

We think this mode may actually be acting as a witness to something else going 'bad', meaning - as you've noticed - it's amplitude does anticorrelate with range but is likely a response as opposed to the cause. I'm trying to figure out how, but for now you should just ignore it. If it starts ringing up steadily/exponentially like other modes, we can look back into damping it. 

TJ, could you increase the set point of the verbal alarm for this mode so we don't hear it unless its quite high?