[Kimura and Ueda (SKS) ]
 On the afternoon of 18 Apr., Ueda-san and me performed   a vacuum leak test for new pressure gage of GVetmx.
The results of the vacuum leak test confirmed that the new pressure gage of GVetmx did not leak more than 1x10^-12 Pam^3/s.

[Kimura, and M. Takahasshi]
 On the morning of 25 Apr., M. Takahashi-san and me performed   a vacuum leak test for new pressure gage of GVetmy.
(See attached photos 1~2)
The results of the vacuum leak test confirmed that the new pressure gage of GVetmy did not leak more than 1x10^-12 Pam^3/s.
After the leak test, we set up protection panel in front of the gage.
(See attached photo 3)

The protection panel for the gage of GVetmx was set up, too.

[YokozaWashimi, Ishikawa, Ozaki, Sudo]

We performed hammering tests (vertical tapping) for the OMC in-vac table.
The tapped points are the table, the base plate, and the ground near the stack1 or 2. 

Yamamoto, Tanaka

We modified the setting from 'Zero_histroy' mode to 'Always_on' mode in the COILOUTF filters for all of suspensions.

Also, we loaded the setting for all COILOUTF filters around 13:30 JST 4/25 2024, except for ETMX, ITMY, PRM, PR2 which someone use in this time. 

According to the health check in January, gain of OSEM #3 (H2) and #4 (V3) are 3 dB and 5 dB smaller than before the earthquake, respectively (fig1 and 2).

Note:

Somehow, SRM IM OSEM TFs have lower gain (2-5 dB) than before the earthquake not only in H2 and V3 but also the others (fig3: case of H3).
Further investigation is necessary.

According to the health check in January, gain of OSEM #1 (H3) has almost no change before and after the earthquake.

According to the health check in January, gain of OSEM #2 (H1) is about 1dB smallerthan before the earthquake (fig1).

I performd health check of IMMT2 (fig1 - fig7).
All TFs seem fine.

I performd health check of IMMT1 (fig1 - fig7).
All TFs seem fine.

[Ikeda, Takahashi]

We checked the OSEMs visually. The flap of OSEM#3 and #4 in the IM was rotated more than 40°.

[Ikeda, Takahashi]

We checked the OSEMs visually. The flap of OSEM#2 in the IM was rotated more than 40°.

[Ikeda, Takahashi]

We checked the OSEMs visually. The flap of OSEM#1 in the IM was rotated more than 40°.

[Takahashi, Ikeda, Hirata, Ushiba]

We checked the IMMT2 suspension visually. There was a small margin of the Pico-motor range for the pitch direction. There was no margin for yaw CCW direction (<1mm). There were not any rubbing magnets in the IM.

[Takahashi, Ikeda, Hirata, Ushiba]

We checked the IMMT1 suspension visually. There were margins of the pico-motor range much enough to adjust both pitch and yaw motion. There were not any rubbing magnets in the IM. When we took the pictures with a fiber scope touching the EQ stop frame, the TM pitch jumped due to a weak joint in the X-Y stage supporting the frame.

[Hirata, Ushiba-san, Ikeda-san]

We checked IR beam position around PR2 HR side Mid-size baffle. (How to make the vertical line is same as klog:29282)
It looks that IR beam positon is about 3.5mm +Y side away from the center of aperture.(IR beam center is 68.5mm and aperture center is 72mm on the ruler.)

The readout of the water fluid has recovered.

[YokozaWashimi, Tanaka, Ozaki, Sudo]

Today we tried to evaluate the seismic isolation of the OMC stacks, using a 3-axial accelerometer (S2315344) and an impact hammer (G1910656).
This is a quick report.

1. Locating the ACC on the OMC vac-table (Fig.1, Fig.2)
2. Tapping each stack (top, middle, bottom of stack1, stack2) with the impact hammer (direction: Fig.3)
3. Picking up each pulse (-0.2/+0.8 sec) and calibrating its transfer functions from impact [N] to acceleration [m/s2] automatically (example: Fig.4, Fig.5)
4. Calculating averages of the events (Fig.6, Fig.7)

[Hirata, Ushiba]

Abstract:

We reconstructed POP forward beam path.
Though beam is still close to the knob of mirror mount just after periscope, the beam doesn't seem clipped.
Now, IR beam hits almost center of the both QPDs when the alignment to PR2 is good.

Detail:

1. Check of beam position at high power beam dump:

First, we requested aLIGNED state for IMMT1, IMMT2, and PRM.
Then, to confirm the good alignment has been kept from yesterday, we checked the beam spot on the PR2 HR target, which is almost center (fig1): good.

After confirming the alignment is good, we checked beam at high power beam dump (fig2).
Beam path seems far enough from the beam dump: also good.

2. Check beam spot on in-vac POM behind PR2:

After confirming the IR alignment to PR2, we checked beam spot on in-vac POM behind PR2 (fig3)
It is hard to say from the picture, but no clip happens at in-vac POM in my eyes.

3. Reconstruction of POP forward beam path:

After confirming beam spot on in-vac POM is not so bad, we started reconstruction of POP forward beam path.
At upper mirror on the periscope, the beam is not center but it seems no clip (fig4), so we keeep it as it is.
Then, we moved upper periscope actuators and hit the beam on the mirror center of lower mirror on the periscope (fig3).
After that, we moved FST1 in JGW-T1909623-v11, because it is hard to avoid clipping without moving the mirror.
Then, we aligned the beam to lower right of the FST1 (fig6) to avoid clipping at the knob of the mirror mount.
Figure 7 shows the current beam spot near the knob, which seems not so bad in my eyes.
After that, we realigned all the downstream and centered the QPDs.

Note:

During the work, on of the actuators of lower mirror mount on the periscope hits the periscope itself and cannot rotate to CW direction (we can rotate it in CCW direction).
So, we cannot move up the beam spot on FST1 without moving periscope mirror upward.
Since I am not familiar with the periscope installed for the POP forward, I didn't lift it up and keep it as it is.

[Kimura, M. Takahashi and Sawada (Hokuto)]
We restarted presuurization of IXC up to 9.8 x 10^4 Pa (~ atmospheric pressure) with G-2 class grade air on morning of 24th/Apr.
Detailes are as followes;
1. Re-start injection the G-2 grade air into IXC
 9:45 Start injection at 7.8 x 10^4 Pa
 10:23 8.3 x 10^4 Pa
 11:09 8.9 x 10^4 Pa
 11:45 9.5 x 10^4 Pa
 12:58 9.8 x 10^4 Pa.
 Stopped injection. 
2. After completion of pressurization to atmospheric pressure, repair of flange leak was done. k-log 29305
3. The amount of gas used for pressurization to 9.8 x 10^4 Pa from 2.3 x 10^2 Pas was 70 m^3.
The breakdown details of the gases used for the vacuum breaking of IXC are as follows:
 63 m^3 of high purity air (7 m^3 x 9 bottles, total 63 m^3)  and 7 m^3 of high purity nitrogen (7 m^3, 1 cylinder)  for a total of 70 m^3.

[Kimura and Sawada (Hokuto)]

 The leak at the IXC cross pipe flange (+Y side) was caused by forgetting to remove the tape that temporarily secures the elastomer seal.

 (See attached photos 1~6)
 The forgotten tape was compressed by the flange, and it is presumed that the leak occurred through a small gap created here.
The tape was removed and a new elastomer seal was attached to the gasket sealing surface to close the flange.
The claw clamps closing the flange (36 in total) was tightened diagonally with torques of 20, 40, and 60 Nm.

A modified drawing of 29285. We mis-understood that the nominal distance from the center of "the optical beam from PRM to PR2" and the center of the "PR2 HR mid baffle aperture" is about 6 mm according to JGW-T1910200-v4, while the correct nominal number of this center-to-center is 4.8 mm according to JGW-T2113078-v2. Hirata-san has confirmed 4.8 mm is correct center-to-center with CAD.