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kentaro.komori - 3:02 Thursday 10 April 2025 (33328) Print this report
Large breathing of PRCL and DARM

From 01:50 UTC on April 10th, the PRCL began exhibiting significantly increased noise in the 10–100 Hz range, exceeding typical levels by several orders of magnitude.
This resulted in a substantial degradation of the DARM sensitivity.

The behavior appears consistent with frequent kicking.
One notable observation is that during this period, the blue curve in the lower panel and green curve in the upper panel (PRCL) and red curve (DARM) on the real-time sensitivity monitor in the control room do not align.
This discrepancy suggests the possibility of nonlinear coupling and it might be a main reason of recent breathing of the DARM sensitivity.
We should investigate the underlying cause of this phenomenon.

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Comments to this report:
hirotaka.yuzurihara - 7:51 Thursday 10 April 2025 (33332) Print this report

> From 01:50 UTC on April 10th,
I guess this is a typo of "01:50 JST". The corresponding time is 16:50 UTC April 9.

I quickly checked the Gauch and found that the strange non-Gaussian noise appeared in the PRCL and DARM.

  • In the case of DARM, this noise appeared at 16:45~18:30 UTC. We can see the drop of the range in the corresponding time at the summary page. After 19:00 UTC, the noise disappeared in the DARM.
  • In the case of PRCL, this noise appeard at 16:45 and looks still remains, as I checked Gauch.  
  • Although the similar phenomena in the PRCL was reported in klog32887, the number of occurance looks different. The new phenomena seems to occur more frequently.
hirotaka.yuzurihara - 14:15 Friday 11 April 2025 (33361) Print this report

Shih-Hong-san and I checked the additional channels. I guess two phenomena were happening simultaneously: (1) the sudden drop of the inspiral range (2) the glitches in the PRCL channel. While the sudden drop of the range happened only during 4/9 16:45~18:00 UTC and disappeared somehow, the PRCL glitches still continued and occurred only at a specific time. We could observe only during 4/9 16:45~4/10 1:00 UTC and 4/10 22:00~4/11 0:20 UTC. The causes are still unclear. The plots are summarized in wiki.

Sudden drop of the inspiral range

  • Figures 1-2 show the coincident change of the DHARD pitch and yaw. There were no coincident changes in other ASCs for arms. (summary page)
  • Figures 3-4 show the coincident change of the PRC2 pitch and yaw.
  • I checked the timeseries of several channels.
    • 15:53 K1:IMC-DOF2_Y_OUTPUT increased and dropped. This channel is the ASC feedback to the MCO. (Fig5)
    • 15:55 ITMX yaw moved --> PRM yaw moved --> IMMT2 yaw moved --> GRX dropped (Fig6)
    • 16:02 DSOFT yaw changed (Fig7)
    • 16:15 PRM pitch moved --> IMMT2 pitch moved. (Fig6)
  • Although I checked the seismometer around this time, there were no coincident signals. (Fig8)
    • 15:40 transient change in 30~100 mHz band
    • 16:05 the transient change in 3~10 Hz band

Glitches in the PRCL channel

  • Shih-Hong-san and I checked the q-spectrograms of these glitches (Fig9). The appearance is different from the arch shape. So, the origin is different from the usual scattered light noise we observed.
  • We checked the PRCL and MICH data, including these glitches. The PRCL glitches are distributed over the 20~200 Hz. But, the frequency band is changing in time. (Fig10)
  • I checked the Omegascan results, and these glitches coincide with the INP2 and PRC2. (Omegascan) (Hveto) The triggered channels by Hveto are different between 04/09 (at that day) and 04/08.
  • We will check the out-of-loop RFPD and PEM sensors located around POP tables.
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