[Yokozawa, Yuzu]

We performed the TCam photo session at 8:06~8:16 this morning. This time, we took only the ITMX image in the Xarm single bounce.

• ITMX Tcam image: [4/1] --> [4/26]
  • horizontal shift = -13.2 pixel = -2.2 mm, vertical shift = +6 pixel = 1.0 mm
  • The position of oplev light also shifted at the same time. The steering mirror in the chamber might have tilted, due to the vacuum evacuation(klog#29307). I will check the ammount of the shift is consistent or not later

Date: 2024/4/26 early morning.

I made the states around "SAFE" of Pcal guardian to be safer.

What I did:

• At "TOSAFE" state:
  • The target value of OFS offset values were changed from 0V to 0.01V because the spec sheet of the AOM driver says it should be 0-1 V and I don't know whether a negative value can make trouble.
  • Added a block to cut the injection signal. (This is not an essential feature, but makes it safer)
  • Added a block to close shutters and open the OFS loops. (This is not an essential feature, but makes it safer)
• At "FAULT" state:
  • Added a block to open the OFS loops.
• Adding decorator
  • Made a "shutter_check" decorator to monitor the shutters, and this decorator was adapt in SAFE and DOWN states. Because of this modification, if you opened the shutter(s) at SAFE or DOWN state, the guardian would detect it and kick to TOSAFE state to close the shutter(s).

Hirata, Akutsu; following 29308 and 29312.

Summary

Confirmed the locations of PR2 HR mid baffle and PRM AR and HR mid baffles. Reinforced STM2. Confirmed that the reflected beam from IMMT2 was far from high power beam dump. Confirmed that the beam from PRM was passing far from PR3 (so the open angle of PRM-PR2-PR3 beam seems 0.02 rad).

Setup

• IMMT1 and 2: ALIGNED state; IMMT2 sometimes went to ALIGNING.
• PRM ALIGNED state; depending on the situation, PAY_FLOAT was called; sometimes, wishing rigorously fix the angle of the mirror, LOCK_ACQUISITION was called.
• PR2: mainly PAY_FLOAT
• IO Guardian: PROVIDING_STABLE_LIGHT, and also HOLD_ALIGNMENT to IMC Guardian additionally.

PR2 HR mid baffle

As was confirmed in 29312, we started with checking the beam position at PR2 HR mid baffle aperture, and seemed the spot was 3.5 mm in plus Y direction with respect to the aperture (Fig. 1), as already reported.

PRM mid baffles

It is difficult to confirm the relative postion of the beam spot at PRM mid baffles due to severe accessibility. We tried several ways (see Fig. 2 and 3, for example; they are respectively of PRM AR and HR side; taken by Miyakawa camera on a tripod; maybe due perspetive, it would be hard to say how much the aperture is dislocated with this way). In the end, using the same method as reported in 29282, we were able to "draw" a vertical line to show the center of PRM AR mid baffle aperture. Then inserting a sensor card with a ruler, we maybe able to say that the beam spot would be ~ 5 mm off-centered in the minus Y direction from this line (Fig. 4), while the noimal number should be 6 mm (JGW-T2214066-v1). So we satisfied at this point.

By the way, Fig. 5 is the beam spot on PRM AR target, while Fig. 6 for PRM HR target. As seen, on PRM AR target, the beam spot was mostly centered; on PRM HR target, maybe due to the refraction, the beam spot was a few mm (2.5 mm? see JGW-D2012020-v2) off-centered in the plus Y direction.

At the same time, ghost beams from PRM on PRM AR mid baffle were checked (Fig. 7). The nominal locations are found in JGW-T2214066-v1, and qualitatively no inconsistency. Also, Fig. 8 was taken from IFI-IMM by Miyakawa IR camera; as seen, "both" side of the aperture edge of PRM AR mid baffle seemed equally shining. The small beam spot left of the main beam spot on PRM would be of surface scatter due to the ghost beam (main incindent -> PRM HR -> -refleceted to AR -> reflected to HR -> exit from AR). When this photo was taken, the camera was set in between the optical beams of IMMT1-to-IMMT2 and IMMT2-to-PRM somehow. The camera hight was somehow set at about the same as those beams. The perspective view seemingly be similar to those in 3D CAD somehow, but it would be difficult to say something definit. At least, qualitatively no inconsistency tendency as follows found; the beam spot on PRM seems left-ward; in the AR baffle aperture, the HR baffle apperture edge could be seen like a crescent...

By the way, in Fig. 8, on the IMMT1 shield, three or four apparent ghost beam spots are seemingly distributed, other than the IMMT1 spot itself. In my observation they are all due to PRM main reflection; When PRM Guadian was at PAY_FLOAT, they were dancing, and stopped when ALIGNED or LOCK_ACQUISITION. My estimation senario is that the PRM backward beam is reflected within IFI, which is made of several optics, and each ghost beam would be reached the IMMT1 shield somehow. One can also see a ghost beam spot in the beam dump in front of IMMT1; this SiC one catches a ghost beam from IFI.

STM2 reinforcement

We set another clamp for the pedestal of STM2 (Figs. 9 and 10; the CL-5 type aluminum one in the deeper inside on the table)while carefully looking at IMMT1T QPDs and POP_FORWARD QPDs; this is related to 24703 (ref: 24697 as well, althogh the main topic of this post was not this bump, but some characteristic was mentioned here). Before and after this work, I checked K1:IMC-IMMT1_TRANS_QPDA2_DC_PIT_DQ spectra, but basically no change around 120-130 Hz area; there was a bump (Fig. 11; blue and green are some reference; red is under experiment; the bump slightly shifted after my works/experiments). What I found was that when I only slightly touch a thick cable for picomotors for STM2, this spectum sensitively responded (it was hard to distingush the response whether I would mere shut the optical beam occasionally by my body or not, though...). I checked if this bump would disappear or not by tentatively fixing this cable with white tapes somehow, but not big changes observed. Anyway, the sensitivity seemingly larger than the other point in the IFI chamber I guess.

Please do some cross-check, and hopefully some treatment should be done before closing this area. Currently, maybe most of the frequency band is dominated by acoustic disturbance, so the next time you should make a tube to connect IFI and IMM chambers to avoid this disturbance.

Light beam position near high power beam dump

As already reported in 29308, The light beam reflected at IMMT2 was passing through far off high power beam dump so no clip should happen (Fig. 12).

Light beam position near PR3

The light beam thourgh PRM was passing through far off PR3's recoil mass (Fig. 13). From this, the open angle of the light beams connecting PRM-PR2-PR3 should be not 0.013 rad, but should be close to the nominal designed value, 0.02 rad; PR2-PR3 distance is about 11 m (see wiki), so 0.02 rad open angle means the beam separation must be 0.02*11 = 220 mm or so, which would be consistent with this photo somehow.

Note

A strange thing; according to JGW-T2214066-v1, the PRM AR and HR mid baffle should be displaced about 9.3 mm nominally; the HR one should be shifted in the minus Y direction. But today we found that there was only ~3 mm displacement. Where 6 mm gap went..? Is Fig. 3 (the center of the target seemd offcententered to the aperture, but I cannot discard this is due to perspective or parallax) related to this issue? Actually the beam spot on this target is a few mm in the plus Y direction according to Fig. 6, but may not be 6 mm. At any rate, 6 mm shifting would be too much. That's why we did not touch both sides of PRM mid baffles.

Ushiba, Hirata, Akutsu

Summary

Reduction of LO for PMC locking, which might be similar but not identical (?) found in the past (19472), happened. This LO power was manually (kind of) recovered, but I have no idea how we could avoid this happening again.

Details

During works 29334, IMC or even PMC suddenly became unable to be locked. In my view, this happened when I requested PROVIDING_STABLE_LIGHT to IO Guadian from PSL_LOCKED. Anyway, Ushiba-kun pointed out that LO level was under the threshold (maybe set at 19472). We were not sure what the "LO monitor" channel meant, but I found that the LO signal generator in the PSL room displayed 8.1 dBm while its nominal power should be 8.6 dBm according to a label attached on its body. I tweaked a knob on the signal generator to tweak the displayed output power to 8.6 dBm, but Ushiba-kun said that the "LO monitor" signal was still slightly under the threshold, so I tweaked it to 8.7 dBm, then PSL and IMC lock came back.

I have no idea why and how this happened. Looking at the "LO monitor" to the past, actually recently sudden reduction of the output power were sometimes observed. So this might repeat again.

One hint might be that I saw a kind of "unstable" state changing in IO Guadtian when I requested PSL_LOCKED when I finished works before lunch (but aruond 13:30). What I did before this was just requesting PROVIDING_STABLE_LIGHT to IO Guardian, and then requested HOLD_ALIGNMENT.

With Hido Shingo

We performed the fine adjustment for the Pcal-X alignment with the ALIGNED state of the ETMX suspension.
We used PCAL_EX1(in Tx module) and PCAL_EX2(in EXA chamber) picomotors to adjust the path 1 so that the paths passed through the design position on the ETM and the center of the RxPD.
We left the Pcal-X laser ON, and the Pcal-X guardian state at OFS_CLOSED_LOW_POWER.

Attached files are showing beam positions on ETM and RxPD.

The total picomotor steps we requested are:

• PCAL_EX1, pico 2 (path 1 yaw): -550
• PCAL_EX2, pico 1(path 1 yaw): -600
• PCAL_EX2, pico 2(path 1 pitch): +400
• PCAL_EX2, pico 3(path 2 yaw): +100
• PCAL_EX2, pico 4(path 2 pitch): +300

The final optical efficiencies were (quick measurement):

• Path 1: 97.0%
• Path 2: 96.5%
• Path 1+2: 96.7%

These are similar to klog28820.

By analyzing the recent TCam images, I identified the mirror center of ETMX, ITMX, and ITMY. When the ETMY or GreenY is ready, we will try to take the ETMY image and identify the mirror center.

Details

• For ETMX, I had an accidental chance to take the TCam for ETMX illuminated by Greenx on 4/23 (during adjustment work of PR2). For ITMX and ITMY, the image was taken on 3/15 (klog#28863).
  • Note that the ETMX image was taken after the evacuation an the ITMX and ITMY images were taken before the evacuation.
• ETMX
  • fitting result
  • overlay with previous reference center (Magenta shows the previous mirror edge and center. Yesllow shows the latest fitting result)
  • From this analysis, I updated the fixed radiuss of 1243 pixel which was computed from the conversion factor of 10/113 = 0.0885 [mm/pixel]. This was evaluated from the metal-scale-insert test(klog#28843).
• ITMX
  • fitting result
  • overlay with previous reference center (Magenta shows the previous mirror edge and center. Yesllow shows the latest fitting result)
  • From the metal-scale-insert test(klog#28843), I evaluated the conversion factor as 10/60 = 0.167 [mm/pixel]. Accordingly, the mirror radius could be 660 pixel. But, this estimation has large uncertainty. If one pixel changes in the estimation, the mirror radius changes 600~733 pixel. I decided to use the fixed radius of 630 pixel which we evaluated by hand fitting with Aogaku members previously, because this value has the small uncertainty than the metal-scale-insert test.
• ITMX
  • fitting result
  • overlay with previous reference center (Magenta shows the previous mirror edge and center. Yesllow shows the latest fitting result)

[Kimura and M. Takahashi]

 To identify the source of the liquid material that entered the EYA tank, three filters of the air compressor and the inside of the connection piping of the dry pumps for vacuum pumping were visually inspected.
As a result of the visual inspection, no traces of liquid material were found inside the filters of the air compressor and the connecting piping of the dry pumps for vacuum pumping.
The smell inside the filter and piping was confirmed by nose, but the same irritating smell observed in the EYA tank was not found.
Three filters of the air compressor were replaced with new ones because more than two years had passed since the last replacement.

[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.)