KAGRA Logbook

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DetChar (General)

hirotaka.yuzurihara - 16:02 Thursday 03 April 2025 (33217)

No scattered light noise and transient noise in PRCL feedback of 4/2 and 4/3

Previously the transient noise (looks like line-ish noise on time-frequency map) was observed in the PRCL data of 2/22~2/23 and reported in klog32887.

I checked the recent Gauch monitor [4/2] [4/3], after the interferometer was recovered. It looks no scattered light noise and transient noise in PRCL feedback signal. Although I checked the q-spectrogram quickly, there was no arch shape on the time-frequency map (which is a feature of the scattered light noise). For further check, I will ask Shih-hong san to deeper analysis.
Figure 1 and 2 show the example of non-Gaussian monitor on 4/2 and 3/20, respectively. The apperance is different. This might happen thans to the treatment of peaks around 20 Hz (klog33197) or the reduction of 127 Hz peak by fixing the STM2 (klog33110).

Images attached to this report

33217_1743662450_K1_LSC-PRCL_OUT_DQ_beg1427677218_time3600_int20_fft1_10_1500_pv_log.png

33217_1743662465_K1_LSC-PRCL_OUT_DQ_beg1426474818_time3600_int20_fft1_10_1500_pv_log.png

Comments to this report:

hirotaka.yuzurihara - 8:54 Friday 04 April 2025 (33235)

This might be a jumping to conclusion... In the yesterday's data (21~22 JST), there was the scattered light noise in MICH feedback channel, even though there is notthing special in the PRCL feedback channel. Figure 1 and 2 show the example. Anyway, the situation for the scattered light noise is changing from the last month (before fixing the STM2).

Images attached to this comment