The STM2 treatment 33110 seems so effective that the coherence between DARM and IMMT1T QPD seems mostly disappeared. Maybe site workers will report more details later.

We performed noise subtraction using DeepClean on the strain data on 2025/03/18.
The witness channels used are:

1. K1:IMC-IMMT1_TRANS_QPDA2_DC_PIT_OUT_DQ
2. K1:LSC-REFL_PDA3_RF45_I_ERR_DQ

The coherence between these channels to the strain channel from 1426341931 s ~ 1426346027 s (4096 s) around 128Hz is shown in Fig.1 and Fig.2.

We trained 3 models focusing on different frequency bands using the data from 1426341931 s ~ 1426346027 s and cleaned the data from 1426346027 s ~ 1426350123 s (4096 s). Here are the frequency bands of these models:

1. model 1: [118 Hz, 135 Hz]
2. model 2: [110 Hz, 156 Hz]
3. model 3: [110 Hz, 135 Hz]

The cleaning results of model 1 are shown in Fig.3 ~ Fig.5 (the ASD of the strain channel, the coherence between the witness channels and strain channel before and after cleaning). The results of model 2 are shown in Fig.6 ~ Fig.8 and the results of model 3 are shown in Fig.9 ~Fig.11.

We can see that the performance of model 3 is the best. The coherence spectrum of K1:LSC-REFL_PDA3_RF45_I_ERR_DQ channel at the training time is very different from the coherence spectrum at the cleaning time, but we can still decrease the coherence between this channel and the cleaned strain channel.

Once the detector is in lock again, we will proceed the same cleaning procedure and see if we still need to subtract beam jitter noise around 128Hz using DeepClean in O4c.

[Kimura]

 The structural difference between IFI and OMC (k-log 32875 ) is the presence or absence of a pumping unit.
Since OMC does not have an ion pump, it is assumed that the pressure drop was faster because water did not adhere to the getter in the ion pump.
 On the other hand, in IFI, moisture adhered to the getters in the ion pump, and the moisture was ionized by the high voltage generated by the ion pump.
In the future, if the ion pump is opened to the atmosphere, it should be cured with dry nitrogen or vacuum-sealed.

[M. Takahashi, H. Sawada, H. Yasui and Kimura]

 We will deliver two He compressors to Y-end.

These He compressors are stock as spair parts for EYC and duct sheild cryo-coolers. 

Here are some comments regarding this report:

• In the original Ncal design, tungsten was intended to be used for the masses, but for this trial, copper was chosen due to its ease of machining and other practical reasons.
• The copper masses measured this time are expected to be used in upcoming tests at KEK.
• Whether the results of this measurement pose an issue in terms of uncertainty is currently under evaluation. (This is expected to be clarified as part of the ongoing calculation of Ncal’s uncertainty budget/requirements.)

With T.Ushiba and K.Tanaka

Summary

• This was the first RF lock of the interferometer since closing the IFI chamber. We successfully achieved an RF lock with 10 W laser power.
• Initial alignment was completed, and the REFL HWP rotation was integrated into the INITIAL_ALIGNMENT guardian to automate the procedure.
• Adjusting the CARM OLTF to set the UGF at 50 kHz allowed us to achieve the lock at 10 W.

Key Activities and Progress

REFL HWP automation

The REFL HWP rotation process was integrated into the INITIAL_ALIGNMENT guardian for XARM, YARM, and PRMI. Proper angle targets (125° for X/YARM, 155° for PRMI) were configured. Code was updated by refering LSC_LOCK.py.

Initial alignment procedures

XARM and YARM alignment was completed; beam positions on the ITM and ETM were adjusted based on camera views. OMC and PRMI alignment followed. For the XARM alignment, we also needed to adjust the alignment of PR3.

CARM OLTF measurement and tuning

Using MokuLab, we measured the CARM open-loop transfer function. The gain was adjusted from -14 dB to -16 dB to shift the UGF from 60 kHz to 50 kHz. After this, we were able to achieve the RF lock with 10 W laser power. Attached figure is the CARM OLTF measured after the adjustment.

[Kimura and Yasui] 
Sub-title: 2025/4/1~2025/4/02 Valve operation records for GVsrm, GVbsx and GVbsy
Abstract:
 This memo is a summary of the GVprm, GVbsx and GVbsy   operations and steps taken to stop the TMPs from April 1 to 2 after the IFI~PRM vacuum chamber was re-vacuumed. 
Below are the steps we decided to take before starting the work.
  Step 1: Set BS safe
  Step 2: Start BS +X, BS+Y side TMPs 
  Step 3: Close GVbsx, GBbsy
  Step 4: Open GVprm
  Step 5: Close TMP's GV at PRM and MCF
  Step 6: Set IFI and IMM oplev safetiy mode
    Monitor pressure changes for a while; if less than 10^-4 Pa, proceed to next step
  Step 7: Open GVbsx, GVbsy
  Step 8: Stop TMP at PRM and MCF
  Step 9: Stop BS+X, BS+Y side TMPs
The series of operations required approximately one day's time.
Three Q-mass graphs are shown to illustrate the change in partial pressure at each point of operation.
(Fig,1 BS Q-mass, Fig.2 ICX Q-mass, Fig.3 IYC Q-mass)
It can be understood that the residual gas composition is changing due to the operation of the gate valves.
The gas partial pressures that change the most are H2, H2O, and O2.
 It is assumed that H2O adsorbed at the time of opening to the atmosphere is separated from H2O due to the high voltage of the ion pump.

The following records are actual working times, pressure values, etc.
 
2025/04/01
Step 1 (+Step 6)
~13:10 Set BS safetiy mode
(Set IFI and IMM oplev safetiy mode)
 
Step 2
13:30  Start BS +X, BS+Y side TMPs 

GVbsx-TMP operation
13:40 TMP GV close，Duct GV open：GVbsx-TMP Qmass:1.6x10^-5 Pa、ION:4.9x10^-6 Pa
13:41 TMP GV close，Duct GV close：GVbsx-TMP Qmass:1.4x10^-5 Pa、ION:3.5x10^-6 Pa
13:42 TMP GV open，Duct GV close：GVbsx-TMP Qmass:1.3x10^-5 Pa、ION:2.1x10^-6 Pa
13:42 TMP GV open，Duct GV open：GVbsx-TMP Qmass:1.5x10^-5 Pa、ION:3.7x10^-6 Pa

GVbsy-TMP operation
13:44 TMP GV close，Duct GV open：GVbsy-TMP Qmass:1.5x10^-5 Pa、CC-10:6.1x10^-6 Pa、ION:4.8 x10^-6 Pa
13:46 TMP GV close，Duct GV close：GVbsy-TMP Qmass:1.5x10^-5 Pa、CC-10:3.6x10^-6 Pa、ION:3.5x10^-6 Pa
13:47 TMP GV open，Duct GV close：GVbsy-TMP Qmass:1.5 x10^-5 Pa、CC-10:3.1x10^-6 Pa、ION:2.1x10^-6 Pa
13:49 TMP GV open，Duct GV open：GVbsy-TMP Qmass:1.5x10^-5 Pa、CC-10:4.9x10^-6 Pa、 ION:4.4  x10^-6 Pa

13:51 PR-2:8.3x10^-6 Pa、SR-2:1.0x10^-5 Pa、PRM:3.4x10^-5 Pa
13:53 GVbsy-TMP CC-10:4.9x10^-6 Pa
13:54 GVbsx-TMP Qmass:1.5x10^-5 Pa
Step 3: 
GVbsx- GVbsy operation
13:55 Close GVbsx, GBbsy
13:56 GVbsy-TMP CC-10:6.2x10^-6 Pa
13:56 GVbsx-TMP Qmass:1.6x10^-5 Pa
13:56 PR-3:9.5x10^-6 Pa、SR-2:1.2x10^-5 Pa、PRM:3.4x10^-5 Pa

Step 4:
GVprm operation
14: 02 Open GVprm
14:10 GVbsy-TMP CC-10:8.8 x10^-6 Pa
14:10  GVbsx-TMP Qmass:1.9x10^-5 Pa
14:11   PR-3:1.4x10^-5 Pa、SR-2:1.7x10^-5 Pa、PRM:2.9x10^-5 Pa
Step 5:
14:13   Close TMP's GV at PRM and MCF
14:14   GVbsy-TMP CC-10: 9.4 x10^-6 Pa
14:15   GVbsx-TMP Qmass:1.9x10^-5 Pa
14:15   PR-3: 1.5 x 10^-5 Pa、SR-2: 1.8 x 10^-5 Pa、PRM: 4.9 x 10^-5 Pa

Monitor pressure changes for a while; if less than 10^-4 Pa, proceed to next step

2025/04/02
Pressure:
9:44  GVbsy-TMP CC-10: 1.7 x 10^-5 Pa
9:45  GVbsx-TMP Qmass:2.6 x 10^-5 Pa
9:46  PR-3: 2.8x10^-5 Pa、SR-2: 3.2 x 10^-5 Pa、PRM: 7.8 x 10^-5 Pa
 
Step 7:
9:47 GV bsy Interlock disable
9:50 IYC Qmass:7.98 x 10^-6 Pa

9:51 Open GVbsy
9:53 IYC Qmass:8.41 x 10^-6 Pa
9:53 GVbsy-TMP CC-10: 1.2  x 10^-5 Pa
9:56  GVbsx-TMP Qmass:2.3 x1 0^-5 Pa
9:58  PR-3: 2.3 x 10^-5 Pa、SR-2: 2.4 x 10^-5 Pa、PRM: 7.6 x 10^-5 Pa
9:59 IXC Qmass:8.1 x10^-6 Pa

9:59 GV bsx Interlock disable
9:59 Open GVbsx
9:53 IYC Qmass:8.41 x10^-6 Pa
9:59 GVbsy-TMP CC-10: 1.0 x10^-5 Pa
9:59  GVbsx-TMP Qmass:1.9 x10^-5 Pa
10:01  PR-3: 2.0 x 10^-5 Pa、SR-2: 2.0 x 10^-5 Pa、PRM: 7.4 x 10^-5 Pa

10:03 GVbsy-TMP CC-10: 9.2 x 10^-6 Pa

10:03  GV bsx&GVbsy Interlock enable

10:07 IXC Qmass:1.0 x 10^-5 Pa

10:13 GVbsy-TMP CC-10: 8.3 x10^-6 Pa
10:12  GVbsx-TMP Qmass:1.82 x10^-5 Pa
10:13 IYC Qmass:9.6 x10^-6 Pa
10:14  PR-3: 1.8 x10^-5 Pa、SR-2: 1.7 x10^-5 Pa、PRM: 7.2 x10^-5 Pa
10:15 IXC Qmass:1.0 x10^-5 Pa
10:16 Close GV BSY TMP
10:17 GVbsy-TMP CC-10: 1.0 x10^-5 Pa
10:12  GVbsx-TMP Qmass:1.82 x10^-5 Pa

10:20 Close GV BSX TMP
10:21 GVbsy-TMP CC-10: 1.1 x10^-5 Pa

10:21  GV bsx&GVbsy Interlock enable
 Wait until the pressure in the vacuum chambers in the central area show decreasing trend

Step 8:
10:24 STOP TMP at MCF

10:35 GVbsy-TMP CC-10: 1.1 x10^-5 Pa
10:35  GVbsx-TMP Qmass:2.1 x10^-5 Pa
10:35  PR-3: 1.7 x 10^-5 Pa、SR-2: 1.8 x 10^-5 Pa、PRM: 7.1 x 10^-5 Pa
10:37 IYC Qmass:1.0 x 10^-5 Pa
10:38 IXC Qmass:1.1 x 10^-5 Pa

10:37 STOP TMP at PRM
10:49 Turned OFF TMP at MCF

10:54 GVbsy-TMP CC-10: 1.1 x10^-5 Pa
10:54 PR-3: 1.7 x 10^-5 Pa、SR-2: 1.7 x 10^-5 Pa、PRM: 7.0 x 10^-5 Pa
10:56 IXC Qmass:1.2 x 10^-5 Pa
10:58 IYC Qmass:1.0 x 10^-5 Pa
10:58  GVbsx-TMP Qmass:2.1 x10^-5 Pa

11:06 Turned OFF TMP at PRM

11:22 GVbsy-TMP CC-10: 1.0 x10^-5 Pa
11:22  PR-3: 1.6 x 10^-5 Pa、SR-2: 1.7 x 10^-5 Pa、PRM: 6.9 x 10^-5 Pa
11:24 IXC Qmass:1.3 x 10^-5 Pa
11:24  IYC Qmass:1.0 x 10^-5 Pa
11:23   GVbsx-TMP Qmass:2.0 x10^-5 Pa

11:31 GVbsy-TMP CC-10: 1.0 x10^-5 Pa
11:31  PR-3: 1.6 x 10^-5 Pa、SR-2: 1.7 x 10^-5 Pa、PRM: 6.8 x 10^-5 Pa
11:31 IXC Qmass:1.3 x 10^-5 Pa
11:31  IYC Qmass:1.0 x 10^-5 Pa
11:31   GVbsx-TMP
11:31   GVbsx-TMP Qmass:Qmass:2.0 x10^-5 Pa
 
Step 9:
11:34~35 Stop BS+X, BS+Y side TMPs

11:42 GVbsy-TMP CC-10: 1.0 x10^-5 Pa
11:42  PR-3: 1.6 x 10^-5 Pa、SR-2: 1.7 x 10^-5 Pa、PRM: 6.8 x 10^-5 Pa
11:44  IXC Qmass:1.3 x 10^-5 Pa
11:42  IYC Qmass:1.0 x 10^-5 Pa
11:42   GVbsx-TMP Qmass:2.0 x10^-5 Pa

11:54~55 Turned OFF BS+X, BS+Y side TMPs

11:56 GVbsy-TMP CC-10: 1.0 x10^-5 Pa
11:56  PR-3: 1.6 x 10^-5 Pa、SR-2: 1.6 x 10^-5 Pa、PRM: 6.8 x 10^-5 Pa
11:57  IXC Qmass:1.4 x 10^-5 Pa
11:57  IYC Qmass:1.0 x 10^-5 Pa
11:57   GVbsx-TMP Qmass:2.0 x10^-5 Pa
 

The segment production at k1det1 has stopped at 18:18:15 JST today. The error was caused by duplicate lines in the cache file. By regenerating the cache file, the segment production started wthout errors.
For the memo, the duplication happened for the K-K1_C-1427533568-32.gwf and the time is 2025-04-01 18:05:50 JST = 2025-04-01 09:05:50 UTC.

Abstract

Details

I offloaded the BF GAS with the FR.

I calibrated the SUMOUT spectrum into the unit of V/rtHz at coil driver output to compare the feedback signals with coil driver noise (~1e-8 V/rtHz).
Figure 1 shows the result (I used the time when IFO was OBSERVATION state, 2025/03/20 13:09:00 UTC).
Red cursors show the coil driver noise level (1e-8 V/rtHz).
Around 40-50 Hz, feedback signals are significantly larger than the coil driver noise except for TMP and MNP.

Calibration:

Since SUMOUT signals send to each coils through EUL2OSEM matrix, it is necessary to consider the matrix elements.
Followings are the summary of the matrix elements.
MNL, IML: 0.5
TML: 0.25
MNP: 2.9585
IMP: 6.3694
TMP: 4.7619

Also, a conversion factor from DAC cnts to voltage is 310 uV/cnt.
So, the final conversion factor from DGS cnts at DUMOUT filter bank to coil driver output are as follows:
MNL, IML: 0.000155
TML: 7.75e-5
MNP: 0.000917135
IMP: 0.00197451
TMP: 0.00147619

Note:

I ignored the effect of dewhitening filter differences because dewhitening filters in COILOUTF and analog coil driver should be canceled.

I changed the setpoint of the heater from 29°C to 27°C at 10:05 JST.

[Kimura and Yasui]

 We closed GV in front of TMPs and turned off TMPs at 9:19AM.

I reduced the current from 0.109 A to 0.107 A.

EX 50K REFBRT HEAD temp is now gradually decreasing.

Abstract:

Tuning notch filters around 40 Hz for EX IM L and P feedback might help mitigate the 40-Hz oscillation and improve interferometer stability.

Details:

To stabilize the interferometer, we need to address the recent 40-Hz oscillation in DARM.
To investigate the cause, I analyzed the spectra of feedback signals for EX pitch and length at the MN and IM stages.

I compared the feedback signal to EX TM L (magenta line in the attached figure) with other signals.

The EX MN L feedback (green line) shows that the 40-Hz peaks are well suppressed by existing notch filters.
The EX MN P feedback is attenuated by the low-pass filter around 40 Hz.

However, in contrast to MN feedback, the 40-Hz peaks are still there in EX IM L and P feedback (red and blue lines) like the TM L signal, suggesting that appropriate notch filter is not inserted.
In particular, judging from Fig.1 in klog:33162, the oscillation frequency might be 41.6 Hz, where a distinct peak is observed in the EX IM L and P feedback signals (marked by a vertical red cursor).
Thus, adding notch filters at 41.6 Hz for EX IM L and P feedback, or anyway tuning notch filters around 40 Hz could mitigate the oscillation.

Additionally, we might be able to prevent violin mode kicks or oscillations at EX by inserting a notch filter around the violin frequency in EX IM L and P feedback.
Currently, a notch filter around 180 Hz does not seem to be inserted in the EX IM L and P filters, but IM L and P can easily excite the violin mode.

So, the hundy GV between PRM and PR3 are still intensionally closed, right?

[Kimura and Yasui]
  We performed helium leak test of the flanges of IFI and IMMT.  
The results of the test is as follows;

* P1: Pressure in the test chamber of the helium leak detector.
 We confirmed there were no vacuum leaks larger than 1 x 10^-12 Pam^3/s. 
 
 After the leak test, we turned on ION pump of IMMT vacuum pump unit and opened GVifi.
We turned on TMP of MCF vacuum pump unit. Currently, the MC and IFI regions are pumping inside the vacuum chamber with two ion pumps and two TMPs.

I started redesign of ETMX hierarchical actuators to reduce the TM actuator RMS.
At this moment, IM started to oscilate at 2.1Hz if the crossover frequency between IM and MN was changed.
On the other hand, we could keep ALS_DARM even if we changed the crossover frequency between IM and TM around 6Hz.
I'm not so sure this modification is enough for reducing the TM feedback signals by a factor of 4 but I will try to use it after recovery of PRFPMI RF lock. 

I added 1 L of water. Now it indicates 80% of the max level.

I offloaded the F2, F3, and BF GAS filters with the FRs.

I offloaded the F0, F1, F2, and BF GAS filters with the FRs.