[Shih-Hong Hsu, Chia-Jui Chou, Hirotaka Yuzurihara, Yi Yang]
This is a report of the noises in PRCL. In 2025/02/22-23, there are three major types of strange noise features by analyzing the RPCL feedback signal (K1:LSC-PRCL_OUT_DQ): none, scattered light, and line-ish noises. This report gives a brief analysis of the line-ish features.
The line-ish kind of noise is transient (< 1 s) and broadband (20 ~ 100 Hz). This kind of noise appears very often on 02/22-23. For example, there are more than 400 lines on 02/22. One can find these lines in
GauCh: https://gwdet.icrr.u-tokyo.ac.jp/~controls/Gauch/day/20250222/index.html
Q-spectrogram: data is summarized in the appendix slide in this JGWdoc
From the result, we can see some features of this line-ish noise in time-frequency maps.
- Transient: The lines happened within 1 s
- Broadband: The lines located around 20 ~ 100 Hz
- Appearance period: more than 400 lines in 02/22 whole day, but not periodic.
- ASD ratio (lines / quiet): 3.01 (only considering 20~100 Hz region); 1.04 (all frequencies)
- Even though this noise appeared in the PRCL control, the LSC_LOCK didn't lose the lock.
The following are some plots of this noise.
- GauCh (Fig. 1)
- K1:LSC-PRCL_OUT_DQ
- 2025-02-22 00:00:00 ~ 00:59:59
- Time series (Fig. 2)
- start: 2025-02-22 00:11:30 (1424218308)
- end: 2025-02-22 00:13:00 (1424218398)
- Whiten time series (Fig. 3)
- fft length = 4 s
- overlap = 2 s
- Spectrogram (Fig. 4)
- Using whiten time series
- fft length = 4 s
- overlap = 2 s
- Q-spectrogram (Fig. 5)
- Using whiten time series
- q = 30
- ASD ratio (Fig. 6)
- ASD_1 start: 1424218308 (without line or other noises)
- ASD_2 start: 1424218368 (with multiple lines)
- length: 30 s
- ASD ratio: ASD_2 / ASD_1
- fft length: 4 s
- overlap: 2 s
