aLIGO LHO Logbook

H1 SEI

richard.mittleman@LIGO.ORG - posted 09:27, Wednesday 13 December 2017 - last comment - 08:57, Friday 05 January 2018(39746)

0.85Hz Peak on the ETMX-ISI

Over the last week we have noticed an anomalous peak in the amplitude spectrum of various sensors on ETMX-ISI, reminiscent of the 0.6Hz peak on HAM 2(?) back when

Looking more closely it seems to be mostly showing up on a few of the CPS channels, St1-H1, ST2-H2 and H3, see the attached screen shot. This data is with the loops on

Images attached to this report

Comments related to this report

richard.mittleman@LIGO.ORG - 14:09, Friday 15 December 2017 (39779)

Link

A little documentation, first(only?) plot shows all five sets of ISI sensors and which channels show the 0.085Hz peaks (a close comparison show that they some channels behave differently from the previous plot)

The second plot is with the ISI in damping only, and the 85mHz peak is gone, not really sure what to say

Images attached to this comment

brian.lantz@LIGO.ORG - 15:11, Tuesday 02 January 2018 (39947)

Link

While looking for something else, I noticed that

ETMY had a similar feature at 0.7 Hz in Aug 2016. Jim and Jeff did some work on it.

see alog 28960.

Not sure if we resolved that one, but maybe it is interesting. I log it here so I don't forget.

brian.lantz@LIGO.ORG - 08:57, Friday 05 January 2018 (40003)

Link

Never mind - the previous issue was with a Trans Mon Suspension which had been left undamped and caused a feature at about 0.73 Hz. This feature is at 0.085 Hz, not 0.85, so is not related.