Here are the results of the investigation of K-Log#15979.

The Picomotor of PR3_BF_L (Motor1) has a connection error, so I checked the cable connection, but found no abnormality in the connection.
Is it not connected because it is not used? The cause was unknown.

With Hirata-san and Ikeda-san

We unjammed the the jammed picomotor. We

• Locked the BF damper
• Locked the BF case to the security structure.
• With an Allen key we turned the nob of the picomotor around a little bit and then Ikeda-san moving remotely from the medm screen. We saw it moving.

The other BF picomotor was not moving. We disconnected some cables and checked them with the multimeter but we didn't find any obvious problem. After we reconnected the cables we tried moving the picomotor using the medm screen and it seemed to move, but it makes a low pitch sound rather than the high pitch sound picomotors usually do. We have experienced a similar problem in one of the Type-B suspensions, but I can't find the klog.

[ikeda, fabian-san, hirata-san].

We measured the value of OSEM when the Picomotor of PR3_BF T was unstuck and the motor was moved by the same amount and returned to its original position.
To confirm that the motor is unstuck, the position after turning it by hand from the stuck position was set to 0[count], and the following values were obtained
-After that, we proceeded from -13000 to -43000 in -10000 increments, and then from -52000 to -362000 in -10000 increments.
The amount moved when stacked was 360000 [count], so I was off by 20000, but this was a simple mistake of moving -3000 at first, but only taking -1000 into account and forgetting to take -2000 into account.

Result

* V1, V2, and V3 of OSEM are very different. 

K1:VIS-PR3_IM_DAMP_Y_INMON: 180 2660 1480 * Pitch and Yaw are now at very different positions than before the start of K-Log#15976.

We checked the data from the time the stack was generated until before it was moved, and found that the position changed around 23:09 (JST) on 2021/02/13.
Pitch is way off at this time.
I would like to discuss how to proceed with this before proceeding.

[Data]

/kagra/Dropbox/Personal/ikeda/VIS/K-Log/20210215/

With Ikeda-san and Hirata-san

Conclusion: the IM must be touching the IRM; more investigation is needed.

In order to assess the health of the system I measured transfer functions (TF).

• I moved BF keystone roughly to zero using coil-magnet actuation.
• I measured the six transfer IM functions: all of them were bad except IM-R. See pictures.
• We applied sinusoidal actuation signals along the different degrees of freedom:
  • IM-L: no motion ( A = 2000 cnt , f = 0.1 Hz).
  • IM-T: there is motion but the TF is not good (A = 1000 cnt , f = 0.1 Hz).
  • IM-Y: there is some motion.
  • IM-V: there is motion, but I'm not sure it's moving free (A = 1000 cnt , f = 0.1 Hz).
  • IM-P: no clear motion (A = 1000 cnt , f = 0.1 Hz).
  • IM-R: there is motion (A = 1000 cnt , f = 0.1 Hz).
• In the last picture it is possible the sudden motion along IM-L. This motion was not produced by actuating on it suddenly but gradually. At some point the IM just moved suddenly and didn't come back when the actuation ceased.

The next step would be:

• Use the IM-Y picomotor to set IM-Y closer to zero.
• Measure TFs again.
• In case this does not fix the problem we must inspect the payload visually.

I continued the health assessment of the IM OSEMs:

• I applied sinusoidal actuation signals at individual OSEMs and all flags seem to be moving, however, they might not be moving freely.
• I compared the free swing motion of PR3 OSEMs with PRM OSEMs, and the displacement measured by the horizontal OSEMs look very different, especially in H1. See the picture attached.
  • The readout in PR3 H1 OSEM looks very noise, while the one in PRM H1 OSEM look far cleaner. The H1 flag might be rubbing.
  • The readout in PR3 H2 and H3 OSEMs have noise-like features also, but not as bad as in H1.
  • The PR3 vertical OSEMs look better although it's possible to see small noise-like features sometimes.
• So far IM-Y has been at 1,783 urad, which is very large. I moved it -15 urad and in the process H1 OSEM jumped suddenly. See pictures.
• I measured IM-L transfer function and it's still bad.

We will go to the tunnel to do visual inspection of the OSEM flags.

With Hirata-san, Ikeda-san and Washimi-san.

Summary: it seems the IM and IRM are touching each other.

See pictures in album PR3 Remedying Work.

In the clean room we inspected the OSEM flags and their positions were as indicated in this diagram in the notebook:

• H1, V1, V2 and V3 indicate there is large amount of positive pitch.
• H2 indicates there is a lot of negative yaw.
• We did not inspect H3 because it's hard to see without opnening the +Y door.

The pitch effect seemed larger so we decided to try to remove it first.

• Assuming the origin of the problem is the pitch of the BF, we added temporary ballast mass on the +X side of the BF top.
• This corrected the pitch in an amount large enough to make the flag seem free from touching, however, the IRM also moved in towards -X such that the OSEM was rendered out of range.
• We removed the ballast mass and saw that the H1 readout is reasonable, actually, relatively close to zero. This suggests the problem might not be the amount of pitch of the BF.

We should aim fix IM-Yyaw first. As reported in entry 16043, before entering ther mine we had set IM-Y close to zero using the picomotor, however, while removing the cloth covers from the chamber duct openings and turning the Koach filters on, IM-Y was disturbed too much. Namely, it went from around zero to about -500 urad. See the attached picture.

Tomorrow we will open the side doors of the chamber and carefully inspect H2 and H3.

With Hirata-san, Ikeda-san and Washimi-san.

See pictures in album PR3 Remedying Work.

Summary:

• The IM and IRM seem to be still touching.
• The IM OSEM measure more than -2 mrad in yaw and the picomotor does not seem to be able to reduce it.
• There are cables touching where they should not. We released the tension in two of them but the improvement was small.
• There seem to be a cable in the IM touching a cable from the IRM. See this picture and this other one.

More information

• All the OSEMs flag seem to properly attached to the magnets. However, it must be clarified that assessment is difficult.
• About cables:
  • One cable from the BF is touching the BF Damper. See this picture.
  • One cable from the BF Damper is touching the security structure before reaching it's clamping point. See the picture in the previous item.
  • Two cables coming out from the IM are touching each other as they go out from the IM after their clamping points (likely this has not created problems so far). See this picture.
  • No Flying Saucer cable clamps were used. See this picture.
  • A cable clamped on top of the BF touches and applies pressure on one of the moving masses on top of the BF after the campling point. See this picture.
  • There are other cables which are almost touching.
  • There seem to be a cable in the IM touching a cable from the IRM. See this picture and this other one.
• For the cables from the first two items above we improvised a temporaty clamping point with a C-clamp. See this picture. The cables are still touching but some of the tension was released.
• We checked H1 OSEM flag and the position improved a little.
• I was not able to reduce IM-Y from about -2 mrad using the picomotor. It decreases by several tens of urad before stopping.

With Hirata-san, Washimi-san and Ikeda-san.

This is a report about the work carried out on Friday 19th of February.

• We checked a couple of cables that looked touching each other in a picture, nevertheless, thay are not touching. Such an impression was created by the angle in which the picture was taken. See this picture and this other one.

• We measured the resistance of H1 OSEM coil. It is 15.4 Ohm. I had the impresion there was a problem with the cable because the flag didn't seem to move when applying coil-magnet actuation.

• We assesed the position of the OSEM flags. See this diagram.

This is a report about work carried out on Friday 19th of February.

I moved the BF to a position similar to the one in which the BF was before the BF picomotor was moved originally. This position is measured with respect to the BF Damper, which is the BF recoil mass holding LVDTs and coil actuators. The idea is to check whether the alignment of the IM is recovered.

Result: the alignment of the IM was not recovered.

Before moving the BF picomotors the position of the BF was

• L, T, V = -731 , 38, 2322 um
• R, P, Y = 483, -840, 5390 urad.
• See this notebook page.

I used the BF picomotor 2 and some BF Damper coil magnet actuator to move it to

• L, T, V = -738 , 51, 2303 um
• R, P, Y = 472, -786, 5325 urad.

The position is not exaclty the same, especially in T and P, nevertheless, it's very similar. The IM alignment did not improve, the IM-Y magnitude is still large:

• IM-L, T, V = 50 , 39, 60 um
• IM-R, P, Y = -165, -676, -2658 urad.

See this notebook page for more details.

It's worth mentioning that the misalignment currently affecting the IM and IRM is large and the differences in  BF-T and P referred to above are relatively small and, likely, they don't play an important role in the problem.

The next step would be use the optic fibre camera to inspect the condition of the OSEM flags. One or more might have moved off from the magnets. By simple visual inpection they all look fine but they are in places where it's difficult to inspect and we might be having the wrong impression.

I reverted the safe.snap becouse Fabian team do not use the suspension in this week. They will work on ETMX repairement.

With Hirata-san.

See pictures in album PR3 Remedying Work.

We inspected the OSEM flags with the fibre optic camera. They all see to be in their respective places. See pictures in the album.

There are also pictures of the mirror taken with the optic fibre camera.

Report about the work done yesterday Tuesday 9th of March 2021.

With Hirata-san.

See pictures in album PR3 Remedying Work.

In order to check the health of the IM-Y picomotor we released the IM from touching the IRM temporarily as follows:

• We locked the BF to the security structure.
• We used the IRM lock screws to move the IRM towards yaw negative until the OSEM flags in the horizontal OSEMs looked roughly at the centre.
• We applied sinusoidal actuation signals to the IM DoF and checked that the IM was following freely the signals.
• We moved the IM-Y picomotor and by ∓100 urad without problems.
• Despite the IM being apprently free, we found the RM stop screw heads were touching the security structure in a way consistent with the large negative yaw of the IM  

This suggested we could use the picomotor to move the IM from around -3 mrad back to zero.

• We did it and we also adjusted the pitch in the process as there was a large coupling.
• We saw the OSEM flags in the horizontal OSEMs moving towards their centres and becoming free.
• As soon as we saw H1 looked completely free we measured IM-L transfer function and got a good result. The IM seems to be free now!
• However, the flags should be moved closer to the centre even more and we'll do this on the next session.

Additionally, we modified the clamping of a cable that was almost touching another cable. See this picture of how it looked before.

I measured the IM transfer functions today with the exception of IM-V because we locked the the SF keystone. The system looks healthy according to the references provided in the diaggui templates.

However, some features look unusual and we should compare with the SUMCOM model and Type-B measurements.

With Hirata-san.

See pictures in album PR3 Remedying Work.

• We checked visually the position of the horizontal OSEMs and they looked better than yesterday when we left. We don't know the reason as no one did any adjustment. Maybe there is a drift favoring the alignment.
• We still moved IM by small amounts in pitch and yaw.
• The horizonal OSEM flags looked relativdely well centers in the OSEMs cavities, but H3 was out of range. There was not much light reaching the photodiode.
• We locked the IRM and IM and adjusted the position of H3 longitudinally. After releasing the payload it read about 64 um, which is good.
• However, after releasing the payload we realized there had been a very large displacement in pitch. H1 became out of range. Likely, this means that by gluing the wire (klog 15844) we didn't fix the problem. More investigation is required.
• The position of the horizontal OSEM flags can be seen in today's pictures in the album. H3 flag is a little low but we can still move the panel down if necessary.
• This is the picture of the cable which was moved away from another cable nearby.
• We checked that the RM stop screw heads were not touching the security structure anymore. See this picture.
• I add a screenshot of the medm screen as a reference.

This morning I measured IM transfer functions with the horizontal OSEMs to make sure the IM was not touching the IRM. The DoF involved are L, Y and T. As can be seen from the pictures, all them look fine, however, the IM-Y transfer function deserves more explanations:

• Although the amount of actuation applied was 1000 counts in the original diaggui file, the actual actuation seen at the output of the test channel was only about 200 counts in amplitude. The coherence was relatively low at some frequencies (see klog 16207).
• I increased the actuation to 2000 counts, giving an effective 400 counts in the test channel. As seen in the corresponding picture attached the coherence improved and the peak 562 mHz dissapear and became a notch.
• A picture shows the time series with the actuation signal with the two different amplitudes.
• It seems suitable to review the reference measurements and compare them with the SUMCOM model.

About the transfer functions:

• The ones for L, T and Y look good, suggesting the IM is hanging free.
• The ones for R and P, which rely in the vertical OSEMs, have an offset. Effect that likely arises from the OSEMs being out of linear range. Notice the coherences are good.
• The SF is locked so I didn't measure the IM-V TF.
• During the measurements the BF keystone was at nominal position given by the setpoint (reached by using about -14,000 counts of actuation). Strangely, this position does not favor the vertical OSEMs; V2 and V3 tend to be out of range.