[Kimura, M. Takahashi and Sawada (Hokuto)]
On the afrenoon of Apr. 16, one failed helium compressor at EXC was replaced.
This compressor is the compressor for EXC's radiation shield cooling cryo-cooler.
The removed compressor will be repaired.

[kimura]

The parallel threaded seal joint with O-ring, which was the cause of air leakage in the valve drive of the GVetmx, was replaced with a regular tapered threaded seal joint.
After the replacement, a leakage test was conducted, and it was confirmed that there was no leakage.
Replacement with tapered thread seal joints is required for all KAGRA φ1000 gate valves, φ800 gate valves, and pendulum valves.
The following three gate valves are awaiting replacement.
1. GVitmx
2. GVitmy
3. GVetmy
 

[Kimura and Ueda (SKS) ]
On the aftenoon of April 16, we performed a vacuum leak test on the retightening flanges around EXV, EXC and EXA.
The results of the vacuum leak test confirmed that there were no leakage of more than 1x10^-11 Pam^3/s at the flanges were retightened this time.

[Takahashi, Ikeda, Aso, Ushiba, Akutsu, +α]

We checked the condition of the stack in the OMC chamber. The screw heads to fix the bellows at the bottom of the 3rd SUS block were touching the 2nd SUS block completely in the X- stack leg. Though we could see the gaps between the other screw heads and SUS blocks, they were very close.

[Ikeda, Takahashi]

We tried to take pictures and movies inside the bottom bellows with the fiber scope. The picture and movie (better quality) show the gap between the pillar and the bellows.

[Hirata, Aso-san]

We applied First contact partially to PRM to remove edges of FC. When we work for AR side, FC string like spider web appeared and attached to the surface. So we applied FC on that string too.

Tomorrow morning, we will try to pill off them.

[Hirata, Ikeda-san, Aso-san]

This morning, Ikeda-san and I pilled off PR2 First contact.

• Waiting time: about 17h
• AR side: We can see small edges at upper part, and thick edges at +Y side(550mm away from the center).
• HR side: +Yside, FC edges were clearly seen. Small dot is near the center(20mm away from the center). It seems that this dot has always been in the same place. We also can see tag foot print, but it was seen before applying FC(600mm away from the center). There was clouded? area upper side of the center. After FC, this clouded area became less clearly visible.(Still we can see it little bit.)

In the afternoon, Aso-san tried to remove FC edges by applying FC partialy.

• AR side: Thick edges were disapperead. We can see new small dots, but those are very small and far from the center.
• HR side: +Y side FC edges were disappeared, but new small edge are appeared. But those are also far from the center.

I uploaded today's photo to KAGRA dropbox.

Additional comment: The difference between the one in bottle and the other in bowl was that the bowl one was left (with its upper opened) in the draft chamber (in operation) for a half day (from yesterday's evening to today's morning) so something might evapolate during this period. The bottle was sealed and was out of the draft chamber.

The speed of melting in the case of acetone is fast or slow or that you need to mix by some bar many times? 

[Takano, Tamaki, Ushiba]

I performed OpLev centering of MNL MNP/Y, MNR/Y, MNV.
Since there is no QPD for MNT somehow, I skipped it, but maybe no problem for vacuum evacuation.

Abstract

I was informed by Uchiyama-san that the IYA vacuum readout on the digital system had stopped.
It was caused by some troubles on the VLAN switch and problem was solved by using an another network switch.
Vacuum DAQ for IYA came back online around 14:27 JST.
 

Details

When I was informed by Uchiyama-san that the IYA vacuum readout was stopped, I couldn't access RaspPi@IYA via the network. So I asked Uchiyama-san to unplug/replug a UTP cable and after then a USB power cable. But RaspPi@IYA was still unreachable. Because it's difficult to continue the recovery work remotely, I went to IYA to access the RaspPi.

According to my inspection at IYA, the RaspPi system seemed to work fine and NIC was lined up properly. At first I doubted a failure on an UTP cable or a LAN port on the switch, but there was no improvement even if I replaced an UTP cable and changed a LAN port. Next, I doubted VLAN setting was something changed. So I changed a network configuration of RaspPi from static IP to DHCP because I expected that IP address for DGS or CATV was assigned instead of one for ICRR. But IP address was assigned as ICRR segment.

This situation seemed to be a problem on firewall like system not a network connection itself. So I stopped RaspPi and connected it to the network switch at BS workstation area for the DGS network and one at Cryocon rack at IXC for the ICRR network. On both network, RaspPi became reachable. So I could localize the problem on the network switch at IYA.

Finally, I asked Oshino-san about the port assignment of two VLAN switches at IYA and the UTP cable for the RaspPi was moved from port#7P of the left switch to port#3 of the right switch (see also Fig.1 and Fig.2). Then, vacuum readout on the digital system came back online around 14:27 JST.

According to the DQ channel as shown in Fig.3, Readout of IYA seemed to stop around 9:53 JST on Feb. 21st. Though it came back online once around 10:48 JST on Feb. 24th, it was stopped again around 14:44 JST on Feb. 27th.

[Akutsu, Tamaki, Takano, Ushiba]

First, we checked the viscosity of the liquid yesterday (movie1: sample in the bottle doesn't seem high viscosity. movie2: sample in the bowl seems high viscosity).
Then, we tested if the liquid can be melt in the following things.

1. Water: not melt and liquid is float on the water surface
2. Ethanol: not melt and liquid sank in the ethanol.
3. Aceton: melt easily

We stored all samples in the draft chamber and put labels below each sample.

[Kimura, Ushiba, M. Takahashi, Sawada (Hokuto) and Ueda (SK)]

 We had closing flange work for IYC on Apr. 15, and closed two cross tube flaneges and one K-800 side flange of IYC.

During this work, we found a white label that has been left in this EYA chamber maybe for 6 years... and detached it.

After the mitiigaing work, We tried to switch the IMC CMS IN1GAIN between 15dB and 16dB with IMC locking. Thanks to the mitigaition, IMC could keep the lock with the swithing (Fig.1). It means that we can increase the input power without any trouble. 

[Akutsu, Ushiba]

We investigated EYA chamber and obtained a sample of the liquid inside the chamber.
We used sysringe with tubes to obtain a sample and stored in the plastic bottole for ethanol.
We also obtained a small amount of the liquid in the stainless bowl.

The  sample volume is about 50 ml and the color of the sample liquid is yellowish (fig1).
Also, I felt the liwuidd is thick during gathering the liquid with syringe.

We stored stainless bowl in the draft chamber to check if the liwuid will be evapolated (fig2, fig3).
We also stored a bottle of the sample at the clean booth of draft chamber (fig4).

[Hirata, Ikeda-san]

We apply First contact to PR2 mirror. We will pill off them tomorrow morning.

１．Lock Suspension（IM→RM→TM）

２．Cleaning（floor, inside chamber by vectra-α with ethanol and vacuum cleaner）

３．Surface inspection of HR and AR side by photo

４．Set FC jig

５．FC apply(AR→HR)

Before appling FC, we saw some edge and footprint of FC on HR and AR side. Those are 500mm or 600mm away from the center.
And also we saw some dots and small dust near the center. We will check it tomorrow morning after pill off FC.

Photo shooting was very difficult like PRM.(Especially AR side) 

I uploaded today's photo to KAGRA dropbox.

I checked OpLev beam path during the installation of SI at IYC.
I confirmed all OpLevs were not clpped by SI.

Since I haven't centered MN OpLevs, OpLev centering should be done before starting pumping.

So, please do not start pumping around IYC area until centering OpLevs of IYC.

For your information. My EYA NAB check on Mar 28, 2024 -> 28997

And the attached photos are additional photos from my directory on that day

Since the earthquake, the pressure at X-27 has tended to increase.
See attached graph.
Periodic inspection records (in Japanese) show no pressure change in X-15~GVmtix.
Inspection-records
Since the pressure increase started immediately after the earthquake, a leak is suspected.
From the estimation, if it is a leak, it is estimated to be 2.8 x 10^-10 Pam^3/s.
Consider leak inspection of X-arms.

This warning seems to vanish around 1:33 according to the records. Anyway, we need more investigation.