Kimura and Furuyado (Shinkoh Denki)
 In order to repair the insulation defects caused by rust in the distribution board PLX-129,
we confirmed the replacement procedure and the on-site situation.
(See attached photos.)
Based on the results of the check, a distribution board repair plan will be prepared and the repair will be implemented.

With Takahumi USHIBA

Purpose and Overview

• Due to tidal motion, an offset gradually accumulates in the feedback signal applied to the IP (Inverted Pendulum).
• The purpose of this work was to offload this offset before the IP feedback signal saturates.
• Because there is LPY coupling, the offloading causes a drift in the PY alignment of ETMX. Therefore, after offloading, the PY alignment was manually adjusted to maximize the green transmission, and the good oplev setpoints were updated accordingly.

Procedure

1. Request RESET_ASC_FEEDBACK and DOWN to LSC_LOCK
   This was necessary to correct the alignment and set all suspensions to LOCK_ACQUISITION.
2. Monitoring TM Oplev and Green Transmission
   TM oplev signals and green transmission were monitored during the procedure.
3. ETMX-IP-ISC2LVDT Filter Bank
   Opened the filter bank of ETMX-IP-ISC2LVDT.
   The objective was to bring the output signal to zero.
   Set the ramp time to 100 seconds.
   Set the gain to 0.
   Waited for 100 seconds.
   Observed that the green transmission decreased (flash level dropped to around 0.4), which was too low for locking.
   Pressed Clear History.
   Restored the ramp time to 3 seconds.
   Restored the gain to 1.
4. Recovery of Green Transmission by Adjusting TM Oplev Setpoints
   Manually adjusted TM oplev setpoints referencing the green transmission value.
   After adjustment, the green transmission recovered to approximately 0.9.
5. Updating Good Oplev Setpoints
   Updated oplev setpoints to reflect the adjustments made during this work today:
   Pitch: 37.2 → 39.1
   Yaw: –9.26 → –1.76
6. Lock Trial
   Performed a lock acquisition trial.
   Successfully achieved lock.

I took the TCam photos for four mirrors at 9:09 ~ 9:19 this morning. The previous work is klog34382.

• ETMX
  • original
  • fitting result
  • previous reference
• ETMY
  • original
  • fitting result
  • previous reference
• For these mirrors, I updated the reference positions. I also re-draw the yellow line shown at the k1mon4. For the other mirrors, we don't need to update the reference positions.

We accepted the SDFs reported on klog34454.

CALEX, CALEY

K1:CAL-PCAL_{EX,EY}_TCAM_{MAIN,PATH1,PATH2}_{X,Y}

A CAL Tcam session was performed to obtain beam position information necessary for Pcal. The parameters have already been updated, and SDF has been accepted.

Operator: Shingo Hido, Dan Chen

Update Time: 2025/07/04 09:03:40

Update Time: 2025/07/04 09:04:08

Update Time: 2025/07/04 09:04:49

Update Time: 2025/07/04 09:05:15

After checking the updated PDF, it seems that all three peaks in question (1st No.2, No.6, and No.9) have issues in the fitting results. I plan to adjust the settings to use a longer FFT length and reanalyze them.

output from check_IFO_status.py

Operators

Takaaki Yokozawa, Hiroshi Takaba, Dan Chen

Shift Time

9:00–17:00 JST

Check Items

• VAC: No issues were found.
• CRY cooler: No issues were found.
• Compressor: No issues were found.
• OBS INTENT: The OBS INTENT was ON throughout the shift.

Note

• There was a period when the interferometer did not lock for an extended time. Just before the unlocked duration reached one hour, an earthquake occurred.
• After that, earthquakes continued to occur sequentially.
• Related klog: klog34448

Today, IFO could not be recovered to even RF-locked state automatically by the guardian for a long time (more than 1 hour).
Since this is the first time that IFO could not be recovered automatically during O4c observing run, I investigated the reason.

Figure 1 shows the ETMX OpLev values before and after the final lock of the interferometer.
Though pitch and yaw values were recorded well, LS oplev values were changed a lot.
This is probably due to the DARM control feedback signals, so it is hard to control.

To avoid the same instability, what we can do is
1. Record LS Oplev values of ETMX and move suspensions so that LS OpLev values becomes close to the one before lockloss.
2. Move ETMX angle during the lock acquisition so that arm alignment becomes good, for example by ADS using GRX.
3. Decouple L2P and L2Y more to reduce the misalignment when LS OpLev values are changed.

Since there are several advantages and disadvantages in the above 3 countermeasures, we need to consider what kind of treatment should be done.

According to klog32643, the peaks got the very high Q values seem to be violin mode:

• Peak of 1st No.2: "EYIMP"

• Peak of 1st No.6: "IYIMP"

• Peak of 1st No.9: "EXIMP"

The PDF file was updated: https://www.dropbox.com/scl/fi/h87b1kxmtvxrobqcc8f35/each_fit.pdf?rlkey=xtrz5wmwzb5t0a5zfgih8tmb0&st=p15q49za&dl=0
I changed plot styles. 

If no local coincident channels were found, that might be caused by, for example, the 5 kHz dither signal being bad.

BNS range channel sometimes shows rapid decreasing as ~1-2Mpc (e.g. Fig.1).
In most cases, decreased BNS range continues 4-5min.
I checked it comes from whether actual noise excess or the method of PSD estimation.
and found it seems come from actual noise excess on error signal (I haven't found coincident witnesses yet).
And also, this noise excess seems to affect an estimation of the time dependent coefficients of calibration.

-----
At first, I made a some sensitivity ASDs around bad BNS ranges. Because BNS range channel has ~4min. delay in actual time, range was re-estimated in offline to compare ASD and rage value in the same time accurately. Figure.2 shows some 64-second long ASDs without overlap in time segments each other. We can see decreased BNS range and noise excess around 100Hz (and also some resonant peaks) in multiple ASDs. This means noise excess continues at least more than 64 seconds. So I saw DARM in-loop signals at the various test points and found K1:OMC-TRANS_DC_{A,B}_IN1_DQ (which is whitened DARM error signals) shows noise excess the most clearly as shown in Fig.3. Now we can see the exact time epoch of the noise excess on DCPD channels, I made 3 ASDs as 1) no noise excess at T1 cursor , 2) small excess at T2 cursor and 3) large excess at crosshair to maximize a effect of this noise excess in Fig.4. These excess seems come from enhancement of some resonant peaks (17 22, 40, 80? Hz) and too large enhancement of resonant peaks seems induced a noise excess of floor level.

In addition (it's a main topic for me), this noise excess makes glitchy behavior on the estimation of time dependent coefficients. For example, time dependency of optical gain fluctuates +/-10% (it's limited by statistical errors because of short integration time) in normal case. On the other hand, it's fluctuate ~30% around the noise excess on the DARM error signal as shown in Fig.5. We may need to apply more strict gating or smoothing in the offline estimation of time dependent coefficients.

With Hiroshi Takaba,

We put the suspension name on the figures reported on klog32632.
We did not do any analysis, but just read this klog and put the suspension names on the figures.

Because of differences in the timing of a file dump processes and/or a delay of re-launching the LL calibration pipeline, a time segment of missing frames in the LL GWF file and one of the re-sent DAQ GWF files are slightly difference. An exact time segment of missing frames in the LL GWF file is [1435460351, 1435461886).

In this period, IFO was in OBSERVING as shown in Fig.1. Plot region is 4096s since GPS=1435459584 which is a same time epochs as the relavant file and missing period is represented by T1 and T2 cursors. On the other hand, there was no SIGNIF (and also LOW_SIGNIF) candidates duirng the relavant period (see also candidate list). So there is no urgency of filling missed frames in the LL GWF file for now. Treatment of this issue should depend on how will we do on the open data.

PDF showing each fitting: https://www.dropbox.com/scl/fi/h87b1kxmtvxrobqcc8f35/each_fit.pdf?rlkey=xtrz5wmwzb5t0a5zfgih8tmb0&st=579p0hzm&dl=0

Operators

Takaaki Yokozawa, Hiroshi Takaba, Dan Chen

Shift Time

9:00–17:00 JST

Check Items

• VAC: No issues were found.
• CRY cooler: No issues were found.
• Compressor: No issues were found.
• OBS INTENT: The OBS INTENT was ON throughout the shift.

Note

• Around 11:00 JST, ground motion increased. It returned to normal around 14:00 JST.
• Around 12:00 JST, the network connection was lost. It recovered around 12:30 JST.
• The following earthquakes occurred near the Tokara Islands:
  • 14:51 JST – Magnitude 5.1
  • 14:59 JST – Magnitude 5.2
  • 15:07 JST – Magnitude 5.1
  • 15:26 JST – Magnitude 5.6

We analyzed the violin mode peaks using approximately 6000 seconds of data starting from GPS time 1433982518 (2025-06-15).

• For the 1st, 2nd, and 3rd violin mode frequency regions, peaks were searched and fitted individually. The fitting results are attached.

• During visual inspection of the fitting results, obviously incorrect fittings were marked with “X.”

• Most of the fitted peaks show Q factors around 1e5. In the 1st mode region, there are three peaks with significantly higher Q values (they look too high...), which are currently under investigation.

• The mirror temperatures at the time of measurement were as follows:

  • Temperature [K]: (IX, EX, IY, EY) = (92, 49, 42, 58)

• A PDF showing each fitting result is also attached.

I just compared BNS and IRXY trans Norm for the recent 22 days as Fig.1

• A very long decreasing trend can be recognized in IRXY_NORM. However, it could be recovered by some adjustments as -19 days, -8 days, and -6 days.
• The BNS reduction around -7 days seems to correlate with the IRXY trans reduction.

Do you find any more characteristic points?