[Shih-Hong Hsu, Chia-Jui Chou, Hirotaka Yuzurihara, Yi Yang]
In klog-35434, Ishikawa-san reported scattered light noise in the STRAIN channel (K1:CAL-CS_PROC_DARM_STRAIN_DBL_DQ) data for 2025-07-15 and 07-16. We investigated the scattered light noise with the method mentioned in JGW-G2416344.
The characteristic feature of scattered light noise found on 2025-07-15 includes:
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Characteristic frequency band: 70 [Hz]
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Time difference between arch-shapes: 1.5 [s]
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Be found in the STRAIN data but not in MICH (K1:LSC-MICH_OUT_DQ) or PRCL (K1:LSC-PRCL_OUT_DQ) data.
While the feature of scattered light noise in April includes:
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Characteristic frequency band: 30 [Hz]
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Time difference between arch-shapes: 1.15 [s]
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Can be found in STRAIN, MICH, and PRCL data.
This result suggests that the source of the scattered light noise in these two periods may be different. A detailed analysis result is also uploaded to the JGW server as JGW-G2516978-v1.
Figure 1: The spectrogram of the scattered light noise in April (left, 4-13) and on 7-15.
The noise is plotted in the spectrogram from the constant Q-transform. The Q value in these is different for a better resolution. f_sc is the frequency of the scattering motion of the source, which is calculated from the inverse of doubling the time difference between the arch shapes.
Figure 2: The spectrogram of STRAIN (left), MICH (middle), and PRCL (right) channels in April (upper, 4-13) and on 7-15 (lower).
The scattered light noise in April appears simultaneously in the STRAIN, MICH, and PRCL channels' data, while the scattered light noise from 7-15 only appears in the STRAIN channel.
