Recently, the vertical, pitch, roll, and violin modes of a specific test mass have been frequently excited during the observation mode.
This test mass is likely ETMY.
The attached figure compares the DARM spectrum in a quiet state with the state where the violin modes were excited.
According to Carl’s violin mode list (klog:32646), these excited modes originate from ETMY.
Do you know when these kicks became frequent? I am just afraid that this is related to the unstable performance of cryocoolers for the EY payload. They were operated from 28th Feb. Which data should we check?
[Komori, Yuzurihara]
I checked the K1:CAL-CS_PROC_DARM_DISPLACEMENT_DQ by applying the bandpass filter with several frequency pairs (160 to 190 Hz with 5 Hz increments). I checked three dates.
This resonance kick didn't happen on the lock (25 min). After this lock, we stop the interferometer work to focus on the OMC work.
Because this analysis required the locked DARM data, there is no way to investigate the data between 2/23~3/3.
The interferometer came back online from the OMC work on 3/3. Figure 1~3 show the time series with the bandpass filters of 180~185Hz, 175~180, and 165~170 Hz, respectively. This resonance kick happened on the lock (40 min). In this case, we observed the frequency band 180~185 Hz was largely excited. Note that the Komori-san's klog shows the excitation at ~167Hz, 187Hz, and 190 Hz.
Figure 4~5 show the time series with the bandpass filters of 165~170Hz and 185~190, respectively. This resonance kick happened on the lock (22 min). In this case, the magnitude of the excitation look comparable for both frequency bands. The excited frequency bands are similar with the Komori-san's klog (~167Hz, 187Hz, and 190 Hz).
I will check the other time with the same configuration, especially the date between 3/3 and 3/10, and also the date before 2/23. If we see the different frequencies that are excited, I guess it's possible to distinguish the kicked suspension and to test the hypothesis of the combination of ETMX and ETMY (Ushiba-san's thought).
Here are the results of the additional analysis. If the magnitude is larger than 0.5, the curve is colored by magenta.
Figure 1, 3, 4 shows no apparent excitation of resonance.
Figure 2 shows some dumped signals. But, the Q-value (dumping duration) looks different from other dumping signals. The amplitude of the signal looks smaller than other dumping signals. I guess the origin of the dumping signal is different from the others.
In Figure 5~7, we can see the dumping signal in 180~185 Hz, which seems to be related to ETMX. Although the neighbor frequency band has the large amplitude and the timeseries data is colored, it's due to the large tail of the line noise.
Note that on 3/6, the interferometer was not locked.
In Figure 8, we can see the dumping signal in 165~170 Hz, which seems to be related to ETMY, and 180~185 Hz, which seems to be related to ETMX. It's possible to be a mixture of these suspensions.
In Figure 9~12, we can see the dumping signal in 165~170 Hz and 185~190 Hz, which seem to be related to ETMY.
Although the neighbor frequency band has the large amplitude and the timeseries data is colored, it's due to the large tail of the line noise.
Is a suspension health check necessary, or should we turn off the cryocooler that shows strange performance??
