23:27;23 ~10 min, 82 Hz injection with 2,000 count (Fig.1.)
Not only the linear peak at 82 Hz, there are +/- 8 Hz sideband peaks when we injected the signal.
8:57:30 - 9:08:00 50 - 100 Hz injection with 15,00 count, 1 Hz resolution
Fig.2. showed the whitened spectrum for DARM, OMC seismometer z direction and geophone inside the OMC VAC table.
No significant shapes were detected in 2 second FFT, if we increased the integration time, we may see some signal in DARM, but even we can see the signal in OMC VAC geophone with 10 times larger than background. we cannot see the peaks in DARM.
Fig.3. showed the silent run for the same channel of the Fig.2.
Even in silent run, there are fluctuated 60-70 Hz peaks, 80 Hz peak sometimes happened.
Compared with Fig.2. and Fig.3, we can see several +/- 8 Hz sideband in several frequencies, but no significant peaks in other frequencies.
This excitation was only detected during the day time with the traffic working time (no signal in noon as shown in Fig.1. (red))
spectrogram (relative to median) of the OMC Geophone
I analyzed the swept sine ground shaking test data performed yesterday morning.
At the injected frequency, the Geophone ASD peak was about 10 times larger than the background.
As Yokozawa-san reported, significant excess was not found in the strain ASDs with 2sec FFT.
I tried 4s FFT and found some excess at around f_inj - 10 Hz.
Cross-coupling peaks with AC power (f_inj + 60 Hz, like klog30475, klog30613) were not found.
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