We wanted to find the relation between the motion of PRM, PR2, PR3 and the scattered light noise in the strain channel.
This report covers two-hour ASD (Fig. 1 to 3) for some optical lever channels at PAY_FLOAT state and analysis of the scattered light noise of 2024.12.13 data, including the spectrogram of strain channel (Fig. 4) and the velocity of PRM, PR2, PR3 (Fig. 5 to 7). The frequencies of the motion of the mirrors are estimated and compared with the frequency of the scattered light noise (klog31911). It is difficult to exclude any mirrors from the possible sources of the scattered light noise from our analysis.
From 2025.01.15 01:13 UTC, Yokozawa-san turned off the damping of the suspensions of PRM, PR2, and PR3. The guardian state was PAY_FLOAT. We made the ASD for three channels:
"K1:VIS-PRM_TM_WIT_L_DQ",
"K1:VIS-PR2_TM_WIT_L_DQ",
"K1:VIS-PR3_TM_WIT_L_DQ"
Detail of the ASD:
start: 1420938798 [s]
duration: 7200 [s]
fftlength: 2048 [s]
xlim: (0.4, 0.5) [Hz]
From the ASD, we can see some peaks from the ASD of each channel:
K1:VIS-PRM_TM_WIT_L_DQ: 0.44971 Hz
K1:VIS-PR2_TM_WIT_L_DQ: 0.46045 Hz
K1:VIS-PR3_TM_WIT_L_DQ: 0.48096 Hz, 0.43262 Hz
For the analysis of scattered light noise on 2024.12.13, we focused on the scattered light noise that happened from 00:16:00~00:17:30 UTC. We made the plots of
1. Spectrogram of Q-transformation of "K1:CAL-CS_PROC_DARM_STRAIN_DBL_DQ" after applying whitening
2. Labeling of the peaks of the arch-shape caused by the scattered light noise in the spectrogram ( JGW-G2416109-v1 )
3. Velocity of the optical levers of "K1:VIS-PRM_TM_WIT_L_DQ", "K1:VIS-PR2_TM_WIT_L_DQ", "K1:VIS-PR3_TM_WIT_L_DQ"
4. Labeling of the peaks on the velocity of the optical levers
The strain is whitened as follows:
1. Read 256 s timeseries from 1418084080 s to 1418084336 s.
2. Estimate ASD by the following parameters
fftlength: 16 [s]
overlap: 8 [s]
method: median
3. Whiten the time series by the ASD
4. Crop 8 s on both ends of the time series
Then, we applied Q-transformation on the whitened time series by the following parameters:
qrange = (30, 30)
frange = (20, 100)
The velocity of the optical levers is calculated by numpy.gradient as the derivative with respect to time on the time series of the optical levers, which are bandpassed with frequency from 0.4 Hz to 0.5 Hz.
