As reported in klog#31187, the commissioner identified fluctuations on the spectrum that are likely to be derived from scattered light. Gauch also shows non-Gaussian behavior in 20~70 Hz bands. I checked the MICH, DARM, and PRCL signals on the data of 2024/10/07 18:00 UTC ~ 10/08 0:30 UTC. [slide]
From the appearance of the time-frequency map, this noise artifact seems to be the scattered light noise.

Detail

• I checked the Gauch (non-Gaussian monitor) results on 2024/10/07 18:00 UTC ~ 10/08 0:30 UTC.
  • Gauch shows the non-Gaussian behavior at 20~70 Hz and the most violent behavior at 20:27 UTC. [Fig]
• I checked the MICH, DARM, and PRCL signals on 2024/10/07 18:00 UTC ~ 10/08 0:30 UTC.
  • In most cases, the arch appeared in the MICH and PRCL signals. See [Fig].
• I generated the Q-transform plot when the scatterer was shaking most violently. [MICH] [DARM] [PRCL]
  • For DARM, only this time, the scattered light noise appeared on the Q-transform plot.
  • For the PRCL signal, the power of the arch appears to fluctuate; one of the two times, it appears to be bright, the other dark. [PRCL] (I'm not sure why)
• I computed the frequency of the scatter object, following the same procedure as in the previous work (JGWdoc).
  • I counted the number of turns on the MICH Q-transform plot --> 17 turns over 20 s --> 8.5 periods over 20 s --> period is 2.35 s --> f_sc = 1/2.35 = 0.425 Hz. The scatter object seems to oscillate with 0.425 +/- 0.025Hz. See also (Fig).
  • I obtained the same results from PRCL and DARM.