MEDM time machine works well.
It can show past values recorded in frame files on MEDM screens and can be launched from the MEDM execute menu.

After choosing a lock back time as relative time, gps time, local time etc. (see also the left windown in Fig.1), a new MEDM screen is launched. Channels not recorded in frame files such as _OUTMON are displayed as white boxes instead of record values as shown in the bottom window in Fig.1

After the alignment work (klog29299), we centered OpLevs and offload actuator outputs by using picomotor.
Followings are the steps we moved for offloading today.

IMMT1 pitch: -330 steps (400 -> 70)
IMMT1 yaw: +14950 steps (-2300 -> 12650)
IMMT2 pitch: +30 steps (-600 -> -570)
IMMT2 yaw: +9325 steps (-8500 -> 825)

[Ikeda, Hirata, Takahashi, Ushiba]

Abstract:

We moved PR2 about 3.3 mm in + Y direction and IMMT2 beam spot about 6 mm in + Y direction.
Then, we centered IR beam on PR2 and check beam spot on PRM, which is also close to the center.
So, alignment to PR2 seems fine now.

Detail:

1. Move PR2 in +Y direction:

For reducing GRX beam light power to identify GRX beam spot center easily, we requested ALS_FIBX guardian to SAFE state (GRX power becomes about 0.8 mW).
First, we moved PR2 so that GRX beam spot on PR2 HR target became nominal.
Since PR2 target was set as projecting PR2 center along IR injection beam (PRM-PR2 line), GRX should be off centered by 3.3 mm (165.48 mm (distance between PR2 HR surface and target) * 0.02 rad (angle between input and reflected beams of PR2)).
Figure 1 shows the GRX beam at PR2 HR target before moving PR2.
Figure 2 and 3 show the GRX beam spot after moving PR2 by 3.5 mm in +Y direction with the traverser.
Now, beam spot seem shifted in -Y direction more than 3 but less than 3.5 mm according to the fig3, which is almost the nominal value.

2. Move IMMT2 beam spot by moving IMMT1:

After moving PR2, we moved IMMT1 so that beam spot on IMMT2 shifted in + Y direction.
First, we requested PROVIDING_STABLE_LIGHT state to IO guardian and wait until alignment becomes good, and HOLD_ALIGNMENT state to IMC guardian not to kick the suspension when blocking the beam to IMMT1T QPDs.
Then, we set a ruler in front of IMMT2 and check the beam spot on the ruler before and after IMMT1 moves.
Figure 4 and 5 show the beam spot before and after moving IMMT1.
IMMT2 beam spot roughly moved 6 mm in +Y direction.

According to the current situation reported in klog29285, we need to shift PR2 beam spot by 5 mm along +Y direction.
Roughly speaking, 6 mm beam spot shift on IMMT2 moves PRM beam spot by 4.5 mm (6*3/4).
Due to PR2 position changes (3.3 mm along +Y direction), PRM beam spot will change 0.8 mm (3.3/4) in +Y direction when the beam is centered to PR2. 
So, in total, PRM beam spot changes by 5.3 mm, which is the same as we would like to move.

3. Center the beam to PR2 by moving IMMT2:

After moving IMMT1, we centered the IR beam on PR2 by moving PR2.
Then, we aligned PRM so that PRM reflection goes to REFL table.
Figure 6 shows the beam spot on PR2 target with aligned PRM, which seems well centered horizontally.
After that, we checked the beam spot on PRM AR target (fig7).
The beam seems hitting almost center.

[Kimura, M. Takahashi and Sawada (Hokuto)]
 We restarted presuurization of IXC up to 7.8 x 10^4 Pa with G-2 class grade air and G-2 class grade N2 on 23th/Apr.
Detailes are as followes;
1. Re-start injection the G-2 grade air into IXC
 8:34 Start injection at 3.2 x 10^4 Pa
 10:25 4.2 x 10^4 Pa
 11:34 5.5 x 10^4 Pa
 11:59 5.7 x 10^4 Pa
 13:06 6.6 x 10^4 Pa
 13:54 7.1 x 10^4 Pa 
 14:41 7.8 x 10^4 Pa.
 Stopped injection. 
2. Injection is resumed on the morning of April 24.
After completion of pressurization to atmospheric pressure, repair of flange leaks will begin.
The amount of gas used for pressurization to 7.8 x 10^4 Pa was pure air (7 m^3 x 7 bottles, total 49 m^3)
and pure nitrogen (7 m^3, 1 cylinder).

[Kimura, M. Takahashi and Sawada (Hokuto)]
 We presuurized IXC up to 3.2 x 10^4 Pa with G-2 class grade air on 22th/Apr.
The specifications of the high-purity air (G-2 grade) used are in klog-25912 for reference;
Detailes are as followes;
1. Start injection the G-2 grade air into IXC
 10:15 Start injection
 10:45 2.1 x 10^3 Pa
 11:40 6.5 x 10^3 Pa
 13:16 1.3 x 10^4 Pa
 14:50 2.4 x 10^4 Pa 
 16:10 3.2 x 10^4 Pa. Stopped injection. 
2. We will re-start injection on on 23rd/Apr. morning.

Reply to 19291. I confirmed that the designed value of open angle of the optical beams connecting PRM-PR2-PR3 is 0.02 rad.

In the attached figure, the "incident" and "exit" angles are at PR2, and are both 0.582 degs as shown. So the open angle is 0.582*2 = 1.16 deg, which corresponds to 0.02 rad.

Attached is fig2 for the original post.

[kimura]
  The parallel threaded seal joint with O-ring, which was the cause of air leakage in the valve drive of the GVitmy,
 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 one gate valves are awaiting replacement.
1. GVetmy

[kimura]
  The parallel threaded seal joint with O-ring, which was the cause of air leakage in the valve drive of the GVitmx,
 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 two gate valves are awaiting replacement.
1. GVitmy
2. GVetmy

The attached figure shows a summary of the current situation IMMT2-PRM-PR2. How do you think about the next step??

• IMMT2's centering is hard to be checked, though.
• Need to also check input GRX spot on the back of PR2 HR target; this spot should overlap on an IR beam reflected at PR2 toward PR3 (not input from IMMT2 to PR2). According to Fig. 3 of 29261, this spot seems also illuminate +Y side of the center line on PR2 HR target, but this should come rather miuns Y side. The target moves together with PR2 traverser, while GRX beam path won't move together with the traverser, as the steering mirror POP-POM is on the suspended table. So this might indicate that PR2 would be dislocated in the minus Y direction now. If we can somehow move PR2 with the traverser in +Y side to some extent (5 mm would be too much? then a few mm...), these mis-centering might be resolved to some extent.

[Nakagaki, Tomura, Kamiizumi, Hirose] 　Thank you very much for helping with the hard work, Nakagaki-san, Tomura-san, Kamiizumi-san.

We did cabling for the WFSf3. 
Cables were routed between mini-racks and IOO0 racks, IOO1 racks, and the REFL optical table. We did not connect them together. 
The details are summarised in the PDF file.

Future plans

• Connecting the power cable to the power strip and checking the current level of the stable power supply in the computer room. This is because the 18 V and 24 V DC power of the mini-rack will be supplied by the IOO0 rack, but when the circuits are turned on at the mini rack, it is possible that the amount of current, especially at 18 V, may exceed the limit values. For this reason it is necessary to check.

Systematic uncertainties on BS transmission and reflectivity measurements were estimated.
Updated results are:

Ts=51.9 +/- 0.2 (stat.) +/- 0.2 (sys.) % for s-pol
Rs=47.7 +/- 0.2 (stat.) +/- 0.2 (sys.) % for s-pol
Tp=77.7 +/- 0.6 (stat.) +/- 0.2 (sys.) % for p-pol
Rp=21.8 +/- 0.2 (stat.) +/- 0.2 (sys.) % for p-pol

Here, uncertainties from the incident angle and the polarization angle are considered.
It seems that they are not responsible for Rs being to low and Rp being too high, compared with the design.

Incident angle error:
 - BS and the incident beam was not aligned perfectly to have the incident angle of 45 deg. BS was in SAFE state.
 - BS reflected beam was not going though the viewport at the gate valve between BS and ITMY. The beam spot was off by ~15 cm over 3.3 m distance. From this, we have estimated that the incident angle error is about 50 mrad (3 deg).
 - Left panel of Attachment #1 is the reflectivity from the coating design, extracted from JGW-T1503347. The middle panel is the zoomed plot around 1064 nm.
 - From this, we can estimate the incident angle dependence as follows.
 - Reflectivity can be written as

R = R0 + dR/dtheta * dtheta

where theta = theta_in/n_eff is the incident angle inside the coating with an refractive index of n_eff (we used n_eff=1.7).
Slight change in theta_in introduces effective coating thickness change, which is equivalent to the laser wavelength change of

dlambda = lambda/cos(theta+dtheta) - lambda/cos(theta)
 = lambda/cos^2(theta)*sin(theta)*dtheta
 
 Therefore,

dR/dtheta_in = dR/dlambda*dlambda/dtheta*dtheta/dtheta_in
 = dR/dlambda*lambda*1/cos^2(theta)*sin(theta)*1/n_eff

 - From the coating design, dR/dlambda is -7e-3 %/nm for s-pol and -3e-4 %/nm for p-pol.
 - From the equations above, this gives dR/dtheta is -4e-2 %/deg for s-pol and -2e-3 %/deg for p-pol (Right panel of Attachment #1).
 - 50 mrad gives dR of 0.1% for s-pol and 0.006% for p-pol.

Polarization angle error:
 - When the polarization angle from s-pol is phi, the measured R will be

R = Rs*cos(phi)**2 + Rp*sin(phi)**2

 - If phi had an error of 5 deg, dR will be 0.2% for s-pol and p-pol.
 - It is hard to explain Rs being too low by ~2%, just from the polarization angle error.

Discussions:
 - Combined systematic uncertainties are 0.2% for all.
 - Rs seems to be too low and Rp seems to be too high, compared with the design.
 - The other source of error could be from the offset of the power measurements from the ambient light.
 - We could also try aligning the polarization angle by maximizing (for s-pol) or minimizing (for p-pol) BS transmission.
 

Takano, Hirata, Akutsu; following 29282.

Afternoon, we checked beam dumps, and ghost beams caught by them in IFI and IMM chambers, and all seemed ok so far. The detailed check will be done next week.

• During this work, C-2-6 blank flange of IFI chamber was detached (Figs. 1 and 2).
• To do this, call PROVIDING_STABLE_LIGHT to IO Guardian, and then zero the ASC gain so that one can walk across the light beam toward IMMT1T (see also Day 1 work: 29261).
• Useful tool: a sensor card attached to a dentist mirror
• In addition, IMMT1 should be kept without oplev feedback tentatively when checking the back of IMMT1; this can be achieved by calling PAY_FLOAT to IMMT1 Guardian.
• Do not hesitate to check REFL DC value and the relevant gige camera image when calling ALIGNED to PRM.
• Refs: invac work finalization in 2022; you can link back from 22244. Highlight would be  21655, 21654, and 21578.
• I would like to repeat that this kind of work requires at least two optical interferometer experiment experts...

Hirata, Akutsu; following 29723.

Summary

We found that the main light beam location at the aperture of PR2 HR mid baffle was almost centered when centering the beam spot on PR2 (to precisely put, PR2 HR target). This means PR2 HR mid baffle is dislocated with respect to the main (forward) beam, unfortunately. My conlusion is that this baffle needs to move about 5 mm in the minus Y direction next week.

Details

As discussed in the morning, we were worried if the current light beam was not be clipped at the aperture of PR2 HR mid baffle. So we started with checking the aperture edge with the Miyakawa-san's IR camera, and no shining in IR found. However, at the same time, we found that the beam passed through the very center (or even shifted in the minus Y direction slightly) of the aperture (Fig. 1).

Nominally, the input beam to PR2 should pass through 6.3 mm shifted in the plus Y direction with respect to the center the aperture of PR2 HR mid baffle (JGW-T1910200-v4). Otherwise the light beam reflected at PR2 toward PR3 would be clipped at this aperture. Because we have not yet determined the "nice" alignment of PR2, we could not make this light beam so far, unfortunately. So we could not check if this reflected beam would be clipped here or not. At any rate, if the input beam would be centered, or in other words, off-centered about 6.3 mm in the minus Y direction with respect to PR2 HR mid baffle, this document says that the reflected beam would be clipped, as the 2.8-sigma edge of this reflected beam is only 4.6mm away from the aperture edge.

So, we need to move PR2 HR mid baffle 6.3 mm (or let's say ~ 5mm) in the minus Y direction.

The drawback of this move is: the invac POP-POM is on the same suspended breadboard as that for PR2 HR mid baffle. When this baffle moves, the balance of the breadboard might be affected, and the alignment of invac POP-POM may also vary slightly. The invac POP-POM is steering (1) POP_FORWARD and (2) GRX to PR3, so both of them should be affected. In short, we have to repeat Day 1 work for GRX, and Day 2 work for POP_FORWARD later. Our hope is that the suspended breadboard does not have vertical springs, so the balance variation might be very small, altough this means no vertical vibration isolation for the stuffs on this breadboard.

Anyway, moving PR2 HR mid baffle will be done in the next week. Hirata-san found several tools used in the past to move this. For reference, see 19291.

Note

• By the way, it would be kind of of-course, no shining maybe due to clipping was found at the aperture edge of PR2 HR mid baffle with the Miyakawa-san's IR camera.
• During this work, we were disturbed by a strange ghost beam, and finally found that this was due to a window attached to a gate valve between PRM and PR3; this GV had been closed. So we opened it.

[Shimasue, Takano, Michimura]

BS transmission and reflectivity were measured to be:

Ts=51.9 +/- 0.2 for s-pol
Rs=47.7 +/- 0.2 for s-pol
Tp=77.7 +/- 0.6 for p-pol
Rp=21.8 +/- 0.2 for p-pol

BS transmission for s-pol is a bit too high, which might be because BS is not aligned (it is now in SAFE state).
We might need to measure them again once BS and ITMs are aligned.

What we did:
 - Followed the procedure in klog 29275 for measuring the BS transmission.
 - For BS reflection, we opened an ICF203 flange labeled HY-2-1 (Attachment #1) so that we can stick the power meter (Thorlabs S310C) from the hole (Attachment #2).

Results:
 - The table below summarizes the results

 - By calculating T = (BS transmitted power) / (incident power) and R = (BS reflected power) / (incident power), transmission and reflectivity were estimated.

Discussions:
 - We noticed that the beam reflected by BS is not going through the viewport at the gate valve. We then realized that BS is not in ALIGNED state, but in SAFE state.
 - This means that the incident angle to the BS might be off by 50 mrad (~15 cm over 3.3 m distance).
 - The measurent tells that AR reflectivity is small enough compared with the measurement uncertainties.

Next steps:
 - Estimate the effect of incident angle from the wavelength dependence from the design.
 - Re-do the measurements with BS and ITMs aligned.

[Shimasue, Takano, Michimura]

BS transmission at ~45 deg was measured to be:

50.8 +/- 0.9 % for s-pol
78.3 +/- 1.6 % for p-pol

They are consistent with the design (see, also, klog 29269 and JGW-T1503347)

What we did:
 - Assembled a tripod setup for injecting the probe beam at IMC REFL area. We had a hard time collimating the beam for a few meters with the beam size smaller than the aperture of the power meter (Thorlabs).
 - The injection bench consists from the laser source -> steering mirror -> Glan laser prism (rotated so that it transmits most of the beam, which was mostly s-pol) -> HWP -> f=-75 mm lens -> steering mirror -> Glan laser prism (rotated to define the polarization of the probe beam) -> f=300 mm lens (Attachment #1)
 - Put the power meter head on a stick so that we can stick it inside the BS chamber (Attachment #2) to measure the power of transmitted beam. IR card was also put in front of the power meter head to find the beam.
 - Brought these setup to the BS area, and put the tripod setup for injecting the probe beam between BS and PR2 chambers.
 - The alignment of the incident beam, both in pitch and yaw was tuned by eye by centering the beam on BS.
 - Measured the incident power at the injection bench, after the last lens (Attachment #3), and the transmitted power at the back of BS (Attachment #4) by holding the power meter on stick by hand. The stick was rested on a ground and/or some vacuum structures so that the head will be stable.
 - The polarization of the probe beam was tuned by eye by rotating the second Glan laser prism (OptoSigma GLPB2-10-25.9SN-7/30). When the white line is vertical, it is s-pol and when horizontal, it is p-pol. The HWP was tuned to maximize the probe beam power.

Results:
 - The table below summarizes the results

 - By calculating T = (BS transmitted power) / (incident power), BS transmission was estimated.

Discussions:
 - The measured values are consistent with the coating design shown in  JGW-T1503347.
 - The incident angle was tuned within a few mrad (beam centering error of a few cm over injection bench to BS distance of 3.3 m).
 - Mis-tuning of the incident angle by a few mrad can be converted into laser wavelength mis-tuning of a few 0.1 %.
 - According to the coating design in JGW-T1503347, HR reflectivity and AR reflectivity does not depend very much on laser wavelength, and probably we will be still be limited by the uncertanties in the power measurement, even if we tune the incident angle more carefully.

Next steps:
 - Measure reflectivity by sticking a power meter from the ICF203 flange between BS and ITMY.
 - Re-do the measurements after aligning ITMs. Use ITM reflection to more carefully align the probe beam to the BS so that the incident angle will be the same with the main beam. (But this is probably uncesessary considering the uncertainties of the power measurement)
 - Estimate systematic uncertainties from the polarization orientation of the incident beam, the incident angle etc.