[Nakagaki, Ikeda, YamaT]

This is similar work of ITMX (klog#36572) and ITMY (klog#36625).
A preliminary research about a situation of both end stations was reported in klog#36635.

I/O chassis of K1EX0 was replaced from V1 (S1604791) to V2 (S2416131).
The front-end computer was also replaced from V3 to V4, but it hasn't been moved from EX0 rack to EXV1 rack due to a miscommunication about laying MTP cables.
We cannot complete this work until purchasing some cables in April.
ADC/DAC noise measurement is planned to be done tomorrow.

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I/O chassis replacement
We replaced the V1 I/O chassis (S1604791) at U18-21 of EX0 rack as V2 I/O chassis (S2416131). In this time, all PCIe cards were moved from V1 I/O chassis to V2 I/O chassis in stead of preparing V2 I/O chassis in which attached spare PCIe cards. Though this procedure involves a risk of taking long time if we need to restore all due to some trouble with V2 I/O chassis, we determined that’s highly unlikely based on the past experiences. (Besides, there’s also the fact that it’s not realistic to prepare same number of spare cards as one of installed cards.) On the other hand, an advantage of this procedure is S-number of used ADC/DAC boards isn't changed.

Front-end replacement
In the original plan, the front-end computer was planned to be moved from the the EX0 rack (1F) to the EX1 rack (2F) as part of the upgrade from the V3 server to the V4 one. An combination of V2 I/O chassis and V3 server has a limitation about a number of attached PCIe cards and EX0 has many ADC/DAC boards. So replacing V2 I/O chassis at EX0 requires to upgrade also the front-end server. Moving front-end server from the EX0 rack to EX1 rack is the most important advantage of using V2 I/O chassis. Because of specification of the cables for V1 I/O chassis, we couldn't separate the servers from analog electronics in the 1st floor of the end stations. Another concern was the increasing number of daisy-chain segments and growing latency across various networks, including RFM.

For this reason, we tried to install a new V4 server in the EX1 rack at first. But a gender of MTP at the splice box was different from one in the discussion in advance. Because MTP pins are very thin and are easily broken, we designed the entire assembly so that the connector of cables which is wired by ourselves would be female. So MTP of breakout cable we have has female connector. The splice box at EX1 rack has unfortunately also female receptor and we couldn't connect them.

Finally, we gave up to install V4 server in the EX1 rack today and installed it at U13-14 in the EX0 rack after removing the V3 server. So the replacement of I/O chassis and front-end computer were finished but the upgrade task hasn't been completed yet. To proceed it, MTP breakout cables with male connector must be purchased. We can resume this task after April.

Side Note
Some SDF differences on the EX0 models remained.

k1tmsx

All differences are accepted in safe.snap (see also Fig.1)

k1calex

It comes from CAL_EX guardian was in FAULT and was paused. It's related to a shutdonw of laser itself (see also klog#36639). For such case, SAFE state should be defined as allowing to stop a laser output without stopping/pausing. Otherwise, any other maintenance cannot be down while the laser output is stopped. In this time, I manually removed all DAC output, then all values accommodated with the set point in safe.snap.

[Kimura and Yasui]

 On March 25, we restarted four duct-shield cryo-coolers called Yea and Yer in the Y-end mirro room at 14:00 as a test run.

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

[Kimura and Yasui]

 On March 25, we switched  form TMP to the Ion pump of the #30 vacuum pump unit connected to the EYV .

After the activation of the #30 Ion pump, we turned off the #30 TMP, dry pump and an air conditioner.

Also, we switched  form TMP to the Ion pump of the #35 vacuum pump unit connected to the beam duct in the 1st floor of Y-end mirror room.

We turned off the #38 TMP and #35 TMP with dry pumps.

[Hirata, Dan, Takahashi]

After installing the new mirror, we released the suspension and the IP in the following order: TM, RM, IM, IRM, BF, F0, and IP. Then we tried to align the TM using the Oplev. Initially, the beam spot of the Oplev was at the upper right. We adjusted the horizontal position with the F0 yaw FR and the vertical position with the IM picomotor (moving mass). The TM was significantly deviated in the pitch direction (maybe due to the lighter new mirror), so 130,000 steps were necessary for the picomotor. We could find the beam spot on the QPD (Picture 1).

We closed the side hatch and the top chamber. The transfer function from the H2+H3 actuator for the IRM dampre to the Oplev yaw "IRM_OLDAMP_Y" was measured (Picture 2). Two modes at 60mHz and 160mHz can be confirmed.

More pictures: https://dac.icrr.u-tokyo.ac.jp/KAGRA/DAWG/CAL/pic/MIF/260324

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).