As posted at the issue, the regular production of segment files at k1det1 has stopped between 3/21 UTC and 3/22 UTC. As I checked the log file, the time of stopping the segment production seems to be 2026-03-22 02:15:00 JST ~ 2026-03-22 02:30:00 JST.  After that, the process to generate segment files restarted from 2026-03-22 14:45:00 JST. 
This is coincident with the occurance time of k1nfs0 issue as reported in klog. 

Since the interferometer was down at the time, I don't think many people would be interested in the segment information for this missing period. If that's the case, then ignoring this missing period is also an option.

[Kimura and Yasui]

 On March 24, we restarted four duct-shield cryo-coolers called Xfa, Xfs, Yfa and Yfs in the center mirro room at 15:00 as a test run.

And we turned on the cooling water unit for the cryo-coolers at the same time,

[Kimura, Yasui, M. Takahashi and H. Sawada] 
 On March 24, as part of maintenance work on the cryogenic cooling units, we removed four valve units from the radiation shield cryo-coolers (IXC  P-53, IXC P-55,  IYC  P-53 and IYC P-55 ).
The removed valve units were packaged and returned to the manufacturing plant, where they will be disassembled and inspected. 

[Takahashi.R, Dan.Chen, Hirata]
We installed new SRM mirror.

・The First Contact on the AR side was peeled off before installation.
・Confirmed that the wedge mark was on the -X side.
・Installed the new SRM mirror and tightened the M4 screws to 1.5 Nm.
・Peeled off the First Contact on the HR side.
・Inspected the surface and found some dots near the center. (pic1)
・We removed the mirror and applied First Contact again. (pic2)
・We reinstalled the mirror and peeled off the First Contact again. The second trial was successful, and the dots near the center were removed. (pic3)
・Finally, we confirmed that the wedge mark was on the -X side again. (pic4)

[Nakagaki, YamaT (Support), Ikeda]

This work is related to K-Log#36625.
We used the new V2 IO chassis to measure the noise levels of the ADC and DAC.
For the DAC measurement, the Whitening Chassis used an available port (on the Board2 side) from S1909738.

During DAC measurements, the Whitening level was set to 42 dB.

[Data]
/users/DGS/measurements/{ADC,DAC}/K1IY1/2026/0324_V2_IO_CHASSIS/

With Shingo

We requested Pcal-X GRD to be SAFE, then stopped the GRD.
Finnally turned OFF the Pcal-X laser source.

[Kimura, Yasui and M. Takahashi]
 On March 23, as part of maintenance work on the cryogenic cooling units, we removed two valve units from the radiation shield cryo-coolers (P-53 and P-55) of EXC.
The removed valve units were packaged and returned to the manufacturing plant, where they will be disassembled and inspected.

 We plan to remove the remaining valve units from the IXC and IYC radiation shield cryo-coolers on March 24.

[Kimura, Yasui and M. Takahasi]

 On March 23, we switched  form TMP to the Ion pump of the #31 vacuum pump unit connected to the EXV .

After the activation of the #31 Ion pump, we turned off the #31 TMP, dry pump and an air conditioner. 

[Kimura, Yasui and M. Takahashi]

 On March 23, we completed maintenance work on the duct-shield cryo-coolers for the  EXC.
Then, we arestarted  the duct-shield cryo-coolers called Xea and Xer   at 15:00 as a test run.

[Takahashi.R, Hirata]
The SRM mirror was transported from Mitaka to Kamioka, and the wedge direction was readjusted.

・The SRM mirror was disassembled and the wedge direction was readjusted. (pic1)
・It was reassembled using a 1.4 mm shim. The specified tightening torques are 0.6 N·m for M3 and 1.5 N·m for M4.
・First-contact was applied to the HR side and then peeled off for cleaning. The process took about one hour. It was easier than when Aso-san peeled it off in Mitaka last week.
・The First-contact on the AR side was peeled off. It had been applied on Friday, March 13. We were concerned that it might be as difficult to remove as it had been from the HR side in Mitaka, but it came off very easily.
・First-contact was applied to the AR side again. (pic2)

Replacement work can be fully conducted.

New fiber cables between EX1 (2F) and EX0 (1F) were already laid.

MTP breakout cable (1-2m) is required to connect the front-end computer to the splice box.

An edge at EX0 side of MTP cable accommodates the input port of V2 IO chassis.

One SMF-SFP module is required for connecting the V4 front-end to the RFM switch by using the RFM board attached to the current V3 front-end.

KVM, UTP for DGS, UTP for DAQ, SMF for RFM, MMF for Timing, and BNC for IRIG-B are necessary in EX1 rack

A new 24V DC power supply for IO chassis is required

If 24V-10A isn't enough, 24V-30A power supply, 5U space and AC-20A source must be prepared.

IO chassis can be replaced but the front-end computer can't be moved to 2F yet.

New fiber cables between EY1 (2F) and EY0 (1F) haven't yet been laid.

Removing V3 front-end and installing V4 one there is current best solution.

MTP breakout cable (1-2m) is required to connect the front-end computer still in 1F and the V2 IO chassis.

All other cables can be reused as ones used by V3 front-end computers.

A new 24V DC power supply for IO chassis is required.

If 24V-10A isn't enough, 24V-30A power supply, 5U space and AC-20A source must be prepared.

We cannot start until purchasing a 20-25m MTP breakout cable for each station in the next fiscal 2026.

All necessary items except 20-25m MTP breakout cable and a cabling work are right there

A same working procedure as ones for ITMs can be applied for ETMs

[Hirata, Washimi, Takahashi]

We removed the 70% mirror (SRM-M) from the Al test mass (Picture 1). At the beginning, we removed the black cylinder from the rear side and removed the mirror holder (Picture 2) by pushing with a Teflon bar from the rear side. We put the extracted 70% mirror on the covered table (Picture 3).

k1nfs0 didn't respond any request from another nodes.
Since it did not respond to commands also from the physical console, I performed a forced reboot.
I also recovered NFS connection (/kagra and /users) on each NFS clients.
If you will find unrecovered nodes (I might forget), please let me know.

-----
I noticed a new console couldn't be launched on the workstations due to a disconnection of NFS region. According to some process logs depending on NFS region, it was dead around 2:30am-2:40am. It's occurred multiple nodes, so it seemed a problem on k1nfs0 or the core network switch instead of workstations. Checking the console of k1nfs0, then it wasn't respond any command with messages shown in Fig.1.

According to the messages, CPU didn't seem to come back to controllable state by the kernel after some kind of task was doing on that CPU core. Anyway, reboot and shutdown commands couldn't be executed, I performed a forced reboot. BTW, BMC interface wasn't available because the primary NIC port was used for the PICO network instead of the DGS network. So I reboot it by the power switch instead of BMC power control interface. When BMC is used as shared LAN mode, the primary NIC must be assigned for the DGS network. We must change NIC settings by NetworkManager or must set BMC as the dedicated LAN mode for the future trouble shooting. Otherwise, physical access will be required during an emergency recovery, making remote recovery impossible.

After rebooting, k1nfs0 could be launched. I checked the boot logs and then, found the boot disk was mounted as RO mode once and then re-moutned as RW mode. On the other hand, there was no SMART report for all disks including the boot disk. Though k1nfs0 is running in normal now, SATA path (cable, controller or route on motherboard) might be asing. It may be a good time to replace the hardware (and also a legacy OS).

Finally, I recovered NFS connection on all clients. Then the system was recovered. But there are several tens of clients and I might miss some of them. If you found unrecovered nodes, please let me know.

Hirata, TakahashiR, Kohara (ATC), Tsuzuki (ATC), Yasugaki (ATC), Ebizuka (Riken), Suzuki (TMT), Akutsu, Aso

We measured the surface figure of the 85% 2-inch SRM with different shim thicknesses to find the suitable mounting configuration.

Conclusion

Consistent with Hirose-san’s report, we concluded that using a 1.4 mm thick shim is appropriate.

Note: We were initially concerned that a 1.4 mm shim might provide insufficient pressure to hold the mirror. However, even when the mount was rotated to various orientations, no displacement of the mirror was observed. In addition, the O-ring adheres to the glass surface and helps maintain the mirror position without requiring strong compression. In practice, when we pulled the ⑤ part out of the mirror mount assembly, the O-ring and the mirror came out attached as a single unit.

Measurement Setup

We used a Zygo GPI-XP interferometer with the following configuration.

A λ/10 reference flat was installed in the interferometer. The SRM under test was mounted in a holder, which was supported by two posts and attached to an adjustment stage combining an XYZ stage and a goniometer.
The temperature of the room was 22.8C, which is similar to the temperature in the KAGRA tunnel.

Results

Shim thickness = 1.4mm

We assembled the SRM holder with 1.4mm thick shims first. This is the recommended thickness in Hirose-san's report.
(We used a combination of two 0.5mm shims and four 0.1mm shims)

The surface figure is beautifully spherical as shown below on the left.
The right hand figure shows the surface figure with the power term removed.

The fitted power term is 571.511nm which translates into the RoC of 462.8m. (Note that the RoC specification of SRM is 458m+/-20m)
The residual RMS after the subtraction of the Zernike terms up to power is 10.728nm. (Note that in Hirose-san's report, this value was 13.3nm for 1.4mm shims).

Shim thickness = 1.3mm

We then removed 0.1mm shims to make the total thickness 1.3mm.

The measured results show clear astigmatism.
The RoC from the power term is 450m. The residual RMS is 103.4nm. While the RoC is still within the tolerance of the specification, the residual RMS is 10 times larger than the 1.4mm case.
This is very similar to the 1.3mm result in Hirose-san's report.

Left: only piston and tilt removed,  Right: power is also removed

Shim thickness = 1.4mm again

We then put the 0.1mm shims back to measure the 1.4mm case again to check the repeatability.

The result is fairly consistent with the previous 1.4mm measurement.
RoC = 458.0m, residual RMS = 13.2nm

Left: only piston and tilt removed,  Right: power is also removed

Closing Remarks

The obtained results are remarkably consistent with Hirose-san's results.
Also it is quite repeatable.
Note that we have two sets of the SRM mirror mount assembly. What we used this time is a different one from the one Hirose-san used. Still the results are quite similar to each other.
There must be a good mechanical reason for this behavior.

I finished the replacement of the Pastavi server at Kashiwa (in computer room of daini sougou tou). Now the new server is working well for the Pastavi.
From the user side, the usage is same as previous. The way to access the server is written in the document.

I tested most of the options in several modes including the noise budget mode. As I checked, the options is available on the new environment.
If you faced any issue, please share the information with me.

The remained task is to develop the new scheme to handle several job by using HTCondor.

Date: 2026/03/19

Member: Dan Chen, Shingo Hido, Misato Onishi

We performed our usual WSK calibration at UToyama.

The results look no problem.

Results

Comparison with Previous Results

Comparing with previous results, no significant issues were found.
Attached graph is the result summary including the latest measured data.