Tanaka, Miyoki, Uchiyama, Yuzu, Takase,

[Summary]

The stuck existed in the Adjuster BD.

[What we did]

After the STM2 cable cut and the STM1 cable fixing, we restarted the search for the stuck position in the water path in the BDs chiller path in the PSL room.

We replaced the Adjuster BD with 30W detectable power detector. Because the water tubes that are attached to the Adjuster BD were fixed on the ceiling metal mesh above around the center of the optical table, we scarcely could move the Adjuster BD just above the edge of the optical table.

At this position, we removed the yellow tube that directly went to the chiller return side above a water basket. We found there was almost no water in the yellow tube. When we injected air by using air duster can into this yellow tube, the return side had also slight water and air. In this sense, this yellow tube had no stuck.

After that, we checked the Adjuste BD itself. We injected air by using the air duster can to the water input where the transparent tube was connected (this tube came from the PMC BD), and checked whether the air could come out from the other side water input where the yellow tube was connected or not. Consequently, there was no airflow could path through the Adjuster BD even though I tried 3 times. After that, I retried the same air injection from the other side. The first trial failed to the air pass through. However, the second trial succeeded in letting the air pass through the BD with some dirty pieces as shown in the photo. After this first air conduction, all air injection trials have succeeded in passing through the BD. So we concluded that, at least this Adjuster BD had stuck.

After that, we injected air to the transparent tube that was connected to the PMC BD to check the airflow to the output side of the chiller through the shutter BD and several tubes. Then we obtained the expected airflow! So we concluded that there was no stuck in PMC BD and Shutter BD and their tubes.

After this klog I found to need one more input port, the all required number of ports for WFSf3 is 10 ports. 
I checked the IOO rack availability today and there were 10 ports available in the IOO0 rack and 1 port available in IOO1.

The following is a summary of the different information when compared to ADC/DAC channel assignment.

• IOO0, ADC0, ch8-ch12: Cables unplugged. There is still a filter for Refcav monitor on the model. (FIG1, FIG2)
• IOO0, ADC1, ch20-ch23: "MCL DMD I&Q" cable is plugged in. No corresponding signal was found in k1IOO0.
• IOO1, ADC1, ch20-ch23: "MZM DC SERBO ADC" cable is plugged in. No corresponding signal was found in k1IOO0.

To reduce electrical noise at the ADC, I need to avoid cabling across the rack. Now I have the following as a plan for the ADC inputs for WFSf3.

1. Plug the ADC into the 10 available input ports in the IOO0 rack.
   → In that case, we need to consider whether to clean up or leave the Refcav monitor filters that remain in the model. I cannot decide now if Refcav will be reinstalled in KAGRA in the future.
2. Add a new ADC to the IOO1 rack to supplement the 8inputs. Also plug it into one empty input on IOO1. Also unplug one unused port on IOO1 and plug it in.
   →However, when cleaning up unused filters and unused signals in the ADC of the IOO1 rack, we need to confirm that we are not reading those signals in the Guardian. 
   The MZM, ISS, and ALS signals are coming to the ADC in the IOO1 rack. At the moment, there is a proposal to use the input port of the ADC used for MZM since MZM is unlikely to be used in the immediate future, and also a proposal to borrow the QPDB of ISS since it is not in use.

I discussed these issues with Yamamoto-san and Ikeda-san.
We have no idea if we will need MZM and Refcav in the future, so we think Plan 2 is appropriate.

From around 14:00, Ushiba-kun tried to LSC lock of IMC and it suceeded. However, ASC did not work even though it seemed to work in the morning time. After several checks of IMMT1 trans and so on, he suspected the laser beam was hidden by something at somewhere. Finally, we found the aluminum foil between IFI and IMMT was shading the beam! The aluminum foils inside seemed to roll inside because of no fixing and its rolling seemed to shade the beam.

Ushiba-kun, Hitrata-san and I fixed this nasty aluminum foil coveres. After that the IMC lock with LSC and ASC was successfully done.

> At the same time, the cleaning in the water vessel of the original chiller was done.
I attached the photos for the record. [before the cleaning] [after the cleaning]

Attached picture shows the current situation inside the IFI chamber.
STM2 pico cables are cut just below the heat-shurink tubes and tied at the STM2 pole with peek tie (red circle in the picture: sorry but cables themselves cannot be seen because they are on the behind of STM2 pole.).
STM1 pico cables are fixed on the optical table with aluminum clamp by M6 screw with vent hole (yellow circle in the picture).

[YokozaWashimi]

We took 4π photos inside the IFI, IMM, and PRM chambers.

https://gwdoc.icrr.u-tokyo.ac.jp/cgi-bin/private/DocDB/ShowDocument?docid=15766

The tube connection information is https://klog.icrr.u-tokyo.ac.jp/osl/?r=22249.

Precisely speaking, Chiller output -> transparent tube -> Shutter BD -> yellow tube -> PMC REFL BD -> transparent tube -> Adjuster BD -> yellow tube -> Chiller return.

So, 

• remove the transparent tube at adjuster BD, then check the water flow.
  • If OK, the adjuster BD and its downstream yellow tube have stuck.
  • If no flow, the stuck point is at upstream.
    • remove the yellow tube at PMC REFL BD
      • If OK, the PMC REFL BD and its downstream transparent tube have stuck.
      • If no, the stuck point is at upstream: Shutter BD and its upstream yellow/downstream transparent tube.

By the way, do you know why the water-cooling type beam dumper was selected? The air cooling type beam dumper for 50W and 150W is enough for our purpose.

[miyoki, tanaka, yuzu, takase]

We replaced the PMC REFL BD with the 50W detectable power meter. the PMC REFL BD was just reset at other place near the original position on the same optical table in the PSL room.

Adter that, Tanaka-kun set the FB laser power at 10W to investigated the lock of PMC and IMC. PMC and IMC was successfully locked, and ASC seemed to work because the IMC output increased after angaging.

At the same time, the cleaning in the water vessel of the original chiller was done.

[Ushiba, Hirata, Tanaka, Miyoki]

After the recovery of the IMC LSC ASC control, ushiba-kun checked the infkuence of the cable touch for the STM2 on the IMMT1/2 trans and pop forward etc.

According to Ushiba-kun opinion, the alignment of the STM2 seemed to be sensitive to the weight load of the cables, not the trembling of the cables themselves. When he lifted up the cables, the STM2 alignment moved temporally, but came bacck to the original position even after stopping to lift up. This implies that we can keep these cables if we can properly fix them on the optical table of the pole. However, it seemed to be quite difficult to perform such thing without mialignment of the STM2 mirror. So we decided that we cut these cables below the pin connections.

While, not so remarkable influence of the cable touch on the STM1 was observed. This is maybe because the a part of cables were winding on the optical table and their weight seemed not to pull the STM1, then they fell to the bottom of the vacuum chamber. So we decided to fix the cables by aluminum clamps on the optical table with a kapton sheet for protection.

I estimated the transfer function from the base plate vibration to the optical table vibration, by
TF(impact@base -> ACC@table) / TF(impact@base -> ACC@base)

I also did the same calculation for the Ground (z) ->Table case, but the results became over 1 for many frequencies. I need to investigate whether my analysis is correct or not...

We found small metal pieces in the water vessel of the chiller. These metal pieces might come from inside the beam dumper as remnants after making a water path by milling.

[Tanaka, Yamamoto, Yuzurihara, (miyoki, uchiyama: remote)]

[Summary]

There seems to be a stuck in the water circulation path for the beam dumpers(BDs). So these beam dumpers were not cooled by water from the chiller. As a result, the temp at the beam dumper at the REFL increased, then the interlock was triggered by its thermometer.

[What we did]

Firstly, we checked the water chiller for the beam dumper. The water level was slightly lower (The top of the metal circulating tube inside the water vessel was slightly above the water level). The chiller itself was on, and the temp setting was 15C(OK). At this moment we did not check whether the water was circulated or not.

Secondly, we checked the interlock box near the entrance door of the PSL  room. We found the interlock was activated with a red LED light. Thirdly, we checked the sealing of the thermometer on the back of the beam dump. The contact of the thermometer seemed to be good.

Then we reset the interlock successfully. After that, we confirmed that the warning message in the FB control application has not vanished and the temp shows ~50C. Then we closed the application and restarted it. The warning has vanished. However, the temp showed ~3C and it became ~ 50C again after pushing the enable button in the application. So, we closed the application again, and made off/on procedure for the FB laser amp itself. After starting the application, the temp showed ~20C and we could keep this temp after enabling the FB laser.

We increased the current to obtain 10W output.

After that, we started the investigation again on the water chiller system for BDs. Tanaka-kun noticed that the air bubble in the water tube did not flow at all. Also he touched the REFL beam dumper and he sensed relatively hot. Then we suspected that there was no water flow in the chiller system. We tried on and off the chiller. Tanaka-kun noticed that the air bubble position shifted a little bit every on/off action and that the tube itself showed a little bit of trembling. However, we could not realize the smooth flow of the air bubble.  Then we checked whether there was returning water flow just before the chiller or not even if the chiller seemed to try to flow water (We sensed some vibration in the chiller itself after pushing the pumping enable button). Then we confirmed that no water returning.

Firstly, we suspected there was something wrong in the chiller itself. So we replaced the chiller with a new one. However, there was also no returning water from the path in the PSL room. To check the chiller itself, we replaced the tube for going from the chiller to the PSL room with a new one, and checked whether there was water output or not. Then we got water flow output. So we concluded that there seemed to be a stuck in the tube-path for BDs in the PSL room.

Because stuck search in the PSL room is a hard work, we gave up today's recovery work.

The FB laser amp was left to be stopped. The seed IR was on.

[to do]

To check the stuck in the tube path in the PSL room, we need to 

• change from OBS mode to Working mode for the PSL room for the long activities.
• remove all parts on the tube path including BDs not to spoil the PSL room with water
• check the stuck point in each part.

If we want to recover the FB at 20W output temporally, we can put air cooling type power meters (50W max and 150W max that we have) instead of these water cooling type beam dumpers. In this case, the interlock system will be temporarily disabled.