I checked the condition around the SRM chamber.

Feedthrough flanges: The D-sub cables were put from the flanges to the cable rack (Picture #1) on the side of the booth.

• ICF203 on the bottom chamber for the IRM damper. The present flange with one D-sub 9pin port will be replaced with the flange with four D-sub 9pin ports (Picture #2).
• ICF203(P6) on the top chamber for the FLDACC H2 (Picture #3).
• ICF203(P3) on the top chamber for the FLDACC H1 and H3 (Picture #4).

SRM mirror holder: I checked the mirror holder in the decicator for OMC. The holder was assembled with the jig (Pictures #5 and #6).

IRM damper: The parts for the IRM damper were delivered and checked in the booth (Picture #7).

Komori, Tanaka

We found that phase margins of the SOFT mode controll, especially Yaw controll, got small. Fig.1-4 show the OLTFs of SOFT mode controll. (Note:Soft mode controll filtters were not changed yet. So the controlls are the same as the O4c ones) 

We considered that the PY coupling in TMS QPDs become larger than before. So we check the PY coupling by injection.

First, we started to check Y2P coupling in CSOFT mode. we injected a 50 mHz sine wave into the loop from the K1:ASC-CSOFT_Y_SM_EXC port and measured the error signal spectra of the CSOFT P and Y respectively. fig. 5 shows the result. The error signal spectra are shown in the left upper panel.  As you can see, 50 mHz peak is in both CSOFT_{P,Y} error even though only Yaw was excited. 

Second, we checked P2Y coupling in CSOFT mode. Fig.6 shows the results. There seems to be 50 mHz peak in CSOFT_P but the peak cannot be seen in CSOFT_Y.  

Similarly, we checked Y2P, P2Y couplings in DSOFT mode. Fig. 7 and Fig. 8 show the results when P and Y was excited, respectively. Like CSOFT mode, Y2P coupling can be seen but P2Y coupling cannot be seen.

[Tanaka, Ushiba, Komori]

Today, we tried a hierarchical control scheme for the yaw modes.
We measured the transfer function from the input of DHARD yaw to each TM oplev signal with the newly designed filter, as shown in the figure.
Assuming that the optical gain is flat, this is regarded as the estimated openloop transfer function.

We designed this filter to achieve a similar response for each suspension, in particular by inserting additional gains in the TM lock filters to match the high-frequency response.
The crossover frequency between the MN and TM is approximately 0.8 Hz, and the overall unity gain frequency is 2 Hz.

We found significant coupling from the pitch mode into DSOFT Y.
Therefore, we will apply this new filter after further decoupling of the pitch and yaw degrees of freedom.

Similar measurement with klog33306.

[Komori, Ushiba]

Abstract:

To measure the FSR of arm cavity, we conducted the cavity scan for X arm.
Analysis will be done tomorrow.

Detail:

To obtain the latest X arm and Y arm length, we tried to perform cavity scan of arms.
Today, we only finished X arm measurement but if the scan method is fine, we plan to perform Y arm scan with the same configuration tomorrow.

Followings are the procedure of the cavity scan.
1. Misaligned ITMY and PRM (request MISALIGNED state for ITMY guardian and MISALIGNED_BF state for PRM guardian).
2. Lock GRX by using XARM guardian (request ALS_LOCKED state).
3. Feedback ALS signals to IMC manually.
4. Increase laser power by rotating HWP at PSL.
5. Scan laser frequency by turning on/off FM1 of K1:ALS-SUM_OFS_SLOWOUT_CALI filter bank.

We modified the ramp time of FM1 of K1:ALS-SUM_OFS_SLOWOUT_CALI filter bank to make the scan speed about 1 kHz/s (100 seconds for ~2 FSR).
The start time of the scan is 8:20:04 UTC and 8:29:10 UTC for forward and backward scans, respectively.
Figure 1 and 2 shows the scan results when increasing and decreasing the offsets, respectively.

It is hard to see the sideband signals in transmission but PDH signals can be seen clearly, so probably this scan can be used for the analysis.
The analysis will be done tomorrow.

Note:

First, I tried to perform cavity scan for X and Y arm at the same time by closing laser shutter for GRY and did not misalign ITMY.
However, maybe due to the coupling between MICH fringes and photosensor signals, ITMX and ITMY were kicked a lot when increasing IMC output power.
So, we gave up scaning X and Y arm at the same time.

Followings are the detailed procedure to feedback ALS signals to IMC manually.
1. change K1:LSC-MCL_GAIN to 1.
2. Turn on FM4 of K1:LSC-MCL filter bank.
3. Close K1:IMC-SERVO_IN2EN switch.
4. Turn off FM2 of K1:LSC-MCL filter bank.
5. Increase K1:LSC-CARM_SERVO_IN2GAIN to 15.
6. Turn on 1st and 2nd K1:IMC-SERVO_COMBOOST.
7. Turn on FM5 of K1:LSC-MCL filter bank.

Diaggui files are stored at /users/Commissioning/data/XARM/2026/0209/.

It is difficult to confirm the exact cause of user code errors, but it is very ikely that the problem was happened due to the very unfortune timing of the subprocess to remove the snapshot files.
To avoid this error, I deleted the function to remve the snapshot files during the OMC scan from the FIND_RESONANCE, FIND_RESONANCE_FOR_10W, and FIND_RESONANCE_FOR_IAL_WITH_RF states while adding this function at DOWN state.

Figure 1 shows the script I modified at DOWN state.
Figure 2 shows the script I commented out at FIND_RESONANCE state, which is same for the other FIND_RESONANCe states.

As reported in klog36315, current LSC_LOCK guardian does not stop even when OMC_LOCK guardian stops and DC PD protection is no more working.
So, I modified the LSC_LOCK guardian so that LSC_LOCK guardian stops at the LOCK_PREP state if the latch switches for OMC is closed (fig1).

Due to the trouble of OMC_LSC guardian, the protection function of DC PDS are not working well.
So, I requested PRFPMI_RF_LOCKED state to LSC_LOCK guardian  not to increase the laser power.

[Kimura and Yasui]
 On Feb. 06, we installed an interlock circuit in the #3 pumping unit near GVbsx.
After installation, we confirmed that the interlock circuit works in the event of a power failure and that the shutoff valve between the dry pump and the TMP is closed.
 Additionally, an air-cooling fan unit was installed on the pump unit's TMP to enable air cooling.

[Tanaka, Komori]

Abstract:

We are continuing the implementation of a new filter to enhance the unity gain frequency (UGF) of DHARD yaw.
Our next approach is to implement a moderate-bandwidth filter that controls only the first and second yaw resonances, while avoiding control of the third resonance.

Details:

In the first trial, we observed oscillations above 10 Hz immediately after enabling the new filter.
This is likely because the gain at high frequencies was too large due to the use of multiple phase compensation filters, causing amplified signals to couple into other degrees of freedom.
Therefore, we decided to abandon, for now, the strategy of controlling all three yaw resonances and instead focus on controlling only the first (0.3 Hz) and second (1.8 Hz) resonances.

We designed the openloop transfer function as shown in the figure.
Phase compensation was implemented using four zero–pole filters, and a notch filter was added to prevent the third resonance at 3.1 Hz from surpassing the unity gain.
When we enabled the new filter, we again encountered oscillations above 10 Hz on several occasions, so additional notch filters were implemented accordingly.

We have not yet successfully closed the DHARD yaw loop.
This is likely because the CHARD yaw loop is still using the conventional low-gain filter.
In the next step, we will apply the same new filter to CHARD yaw and attempt to close the {D, C}HARD yaw loops simultaneously using the new filter.

I found that OMC_LSC guardian stops due to the camera errors.
I'm not so sure what happens but is it related to the maintenance work today?

I offloaded the IM V OSEMs with the picomotors for pitch. It was performed in ALIGNED mode.

[Miyakawa, YokozaWashimi]

We installed 4 ahakers installation in the PSL room.

1. Near the final periscope
2. Near the ACC3 and the Laser source
3. & 4. Near the suspect mirrors

This update proposal was applied in klog#36305.

Spectrograms for the  large shaker tests.

Spectrograms for the  small shaker tests.