Whether we have bad luck today, or we had been too lucky?
The following plot comapres spectra of TM oplevs of ITMX/ETMX, at 8am JST yesterday and today.
Mirrors were moving in 0.2Hz and it disturbed locking.
The seismic motion is twice bigger than yesterday and you can see mirrors were moving in coherent. Therefore we judged it caused by seismic motion.
What is the cause of the seismic motion?? Maybe there was no big earthquake. Because of low pressure??
I think that the suspensions have no problem.
The increase in the PIT and Yaw motion (clearly visible in the spectra in the range [0.1,0.3] Hz that you show) is due at the variation of microseismic condition. Indeed, when the bad weather condition occours (strong wind, rough sea, etc. ..) the amplitude of the microseism in the range [0.1 0.3] Hz increas. Therefore it seems plausible that today you can not locked the cavity if the angular controls on the marionette and also Inertial control on the IP are not engaded.
I seem to agree with Lucia.
[Note]
= ETMX =
First, I was hpoing this might caused by coupling from vertical motion (since the GAS-keystones and the BF were oscillating with amplitude of ~10um(/~10urad) in RMS, in ETMX) and thus I impelemted 2 damping filters at F1 and BF-GAS of ETMX(Not much tuned). Those vertical motions were damped in some extence though, the issued peaks were not dissapeared, i.e., coupling from vertical was not the cause.
Before/After:
Thank you Lucia and Fujii-kun.
> Therefore it seems plausible that today you can not locked the cavity if the angular controls on the marionette and also Inertial control on the IP are not engaded.
If so, the controls on the marionette or inertial damping will be necessary, especially in winter...
[Just note]
It seemed that the BF-body of both the suspension was oscillating with relatively larger amplitude at aound 0.2 Hz (around the main pendulum resonance). It seemed that those peaks were not damped with BF-LVDT controls.
ITMX / ETMX
