[Kimura and M. Takahasi]

 On March 18, we switched  form TMP to the Ion pump of the #36 vacuum pump unit at the Y-end .

After the activation of the #36 Ion pump, we turned off the #36 TMP and dry pump

[Kimura and M. Takahashi]

 On March 18, we completed maintenance work on the duct-shield cryo-coolers for the  EYC.
We are planning to restart the duct-shield cryo-coolers starting March 23, which will also serve as a test run.

[Kimura and M. Takahashi]
 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 EYC.
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, IYC, and EXC radiation shield cryo-coolers early next week.

KAGRA Pcal-X updates (2026/03/18)

Workers: Kohei Mitsuhashi, Dan Chen

We performed monthly Pcal-X calibration on 2026/03/18.

After the calibration, we updated EPICS parameters related to the Pcal-X system. No issues were found.

I offloaded the F0 and F1 GAS filters with the FRs.

[Kimura and Yasui]

Parts replaced during maintenance work
1. Absorber in the helium compressor
2. Filter unit at the supply side
3. Gas replacement inside the cold head in accordance with SHI work procedures
4. Disassembly and maintenance of the valve unit at the SHI factory
5. Gas replacement in the compressor and flexible tubing
(1) Helium gas used: G-1 grade
(2) Filling pressure: 14.8 bar

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, Kohei Mitsuhashi, Dan Chen

Update Time: 2026/03/18 07:41:38

This work is continued from klog36589

## GAS control modification

According to yesterday's results related to GAS, there seem to be gain peaking at 3-4 Hz. So I reduced {F0,F1,BF} gains to -6dB. After that I measured their OLTFs when SR2 is in the LOCK_ACQUISITION state. Fig.1,2,3 show the results. Unfortunately, OLTF could not be measured well maybe due to the coupling between GAS controls. Acoording to loop suppression (IN2/EXC), their controls seem to work well and the peaking around 3-4Hz becomes smaller. Fig.4 shows the error/feedback spectra. The peaking seems to be disappeared although each residual GAS motion seems to be not changed so much.

## IM DAMP roll off modification

I also modified the roll off filters for IM DAMP {L, P, R, Y}. As for T and V, elliptic filter was also not used in SR3. So I did not touch them in this time. (Maybe it is better to change)

I measured the OLTFs after the modification. Figure.5, 6, 7, and 8 show the OLTFs of IM DAMP {L,P,R,Y}. Also Fig. 9 and 10 show the error/feedback spectra. the feedback above 10 Hz was rolled off successfully.

[Kimura and Yasui]

 At around 10:00 a.m. on March 17, we stopped the vacuum pumping in the Q-mass piping, opened the cryostat-side GV, and connected the Q-mass.
The pressure inside the piping before opening the cryostat-side GV was 1.8×10⁻⁴ Pa, and after opening the GV, it was 4.4×10⁻⁵ Pa.
 We then installed an analysis unit on the Q-mass piping. The final pressure inside the piping was 3.5 × 10⁻⁵ Pa.
We then removed the vacuum pumping unit from the piping.

[Kimura and Yasui]

 On March 17, we completed maintenance work on the duct-shield cryo-coolers for IXC and IYC.
Maintenance work on the duct-shield cryo-coolers for EXC and EYC is also scheduled to be completed by the end of this week.
We are planning to restart the duct-shield cryo-coolers starting March 23, which will also serve as a test run.

Workers: Kohei Mitsuhashi, Dan Chen

We performed monthly Pcal-Y calibration on 2026/03/17.

After the calibration, we updated EPICS parameters related to the Pcal-Y system. No issues were found.

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: Kohei Mitsuhashi, Dan Chen

Update Time: 2026/03/17 15:31:24

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

[Washimi, Takahashi]

We replaced the broken signal generator (SG) NF1956 with the embedded SG card for the LVDT driver (S1807787) in TMSX. We opened the driver chassis and inserted the SG card. The output of the SG card was connected to "REF IN" port on the front panel. The signal was set to 10kHz in frequency and 7Vp-p in amplitude.

The new Pastavi server was purchased with the SEO budget and delivered to the KAGRA site. I performed the initial setup on the server and copied the data viewer system. After completing the preparation at the KAGRA site, I sent it to Kashiwa last Friday. I will replace the server in Kamioka this Thursday. 
Please note that it may take some time to recover the noise budget mode. I expect it to be restored within a few days.

Note

• Because the OS version jumped significantly from 9 to 12, many modifications to the settings were necessary.
• The cgi package has been deprecated from Python 3.13. Although it is possible to use legacy-cgi, its behavior was slightly different from what I expected. Therefore, I decided to use Python 3.12. In the future, it may be necessary to redevelop Pastavi using another framework or tool.
• Installation of the frameL was not as straightforward as in the previous environment  (actually I just wanted to use the FrChannels command). The procedure for installing lal (or framel) using apt is described on the following pages: [wiki] [IGWN debian repo]

ITMX has successfully reached the LOCK_ACQUISITION state.
We will leave it in this state for a while to verify that no issues arise with the new V2 I/O chassis.