(Work on 13th)
[Hirata, Washimi, Takahashi]
This is a rapid report. Details will be reported later. We started assembling the new mirror. We found that the new mirror (85%) is thinner than the old mirror (70%). Measured thickness with vernier calipers was 7.9mm for the new mirror and 9.6mm for the old mirror at the edge marker. The thickness of the shims (#9 in Picture) was 1.5mm. Therefore, the flange (#5 in Picture) couldn't fix the mirror even if the shims were not used.
[Kimura and Yasui]
On March 13, we replaced the Q-mass for the IXC, whose filament had broken. (Photo 1)
As part of this replacement, we added a pressure gauge and a valve. (Phpoto 2)
After the replacement, we conducted a vacuum leak test, and the leak rate was found to be 1×10⁻¹² Pa·m³/s or less. (Photo 3)
Following the leak test, we are continuing to pump down the Q-mass connection piping.
We plan to open the valve between the Q-mass and the IXC on or after March 16 to connect the Q-mass to the IXC.
PoE doesn't seem to be enabled on the camera switch at the server room and I couldn't enable it because IP address of this switch is missing.
So I moved a2A5328-4gmPRO near the camera switch at the IOO0 rack on which PoE is enabled and a2A5328-4gmPRO came back online again (Fig.1).
But, I found that the switch at IOO0 rack and one at server room were only linked at 1G, contrary to what I had been told.
For this reason, I haven't yet done the test with the network which should have sufficient capability.
Anyway, both a2A5328-4gmPRO and acA4112-8gm are now online.
-----
In today's work, I understood the camera network configuration is completely chaos. IP address information on JGW wiki was not true for 3 of 6 network switches. I tried to do ping-search beyond L3 segment by using virtual NIC but 2 of 6 switches including the core switch at the server room are still missing. 2 of found 4 switches don't have a reachable route because the inconsistency between the physical and logical connections. A drastic reassessment is required.
As mentioned above, the link speed between the IOO0 and the server room is 1G though it should be 10G. According to my check, I couldn't find any reason why the link speed between IOO0 and the server room is limited as 1G on the switch at the IOO0 rack. So I'm doubting it comes from the settings on the core switch at the server room. But the core switch is still missing. So we need salvage it at first. Or using USB-RJ45 console cable if someone have...
Date: 2026/03/13
Member: Dan Chen, Misato Onishi
We performed our usual WSK calibration at UToyama.
The results look no problem.
| Case | Alpha (Main Value) | Alpha (Uncertainty) |
| Front WSK, Back GSK | -0.910922 | 0.000075 |
| Front GSK, Back WSK | -0.908846 | 0.000225 |
Comparing with previous results, no significant issues were found.
Attached graph is the result summary including the latest measured data.
I measured the OMC PD dark noise wih several configurations.
Figure 1 shows the results (legend on the left top graph represents the setting of the measurement of each color plot).
Blue line (measured in 2025) and pink line (measured today) can be compared directly because the measurement setting of these two are the same.
Though the PDB spectrum was worse in the previous measurement (klog36277), the measured spectrum today seems good.
I'm not so sure why the PDB noise level was recovered.
This morning, I fund ETMY was tripped due to the watch dog of F2 GAS as shown in fig1
According to the seismometer signals, this trip seemed coincident with the earthquake (fig2).
So, I just recovered the ETMY from the tipped state.
[Kimura and Yasui]
On March 12, we switched the vacuum pumps in the central mirror chamber to ion pumps.
The TMP and dry pumps currently in operation are pumps #40 and #41 directly below the arm-side GV.
All other TMP and dry pumps in the central mirror room, including those on the 2nd floor, have been stopped.
The vacuum pumps at X-end 1F have also been switched to ion pumps.
Locations where the switch to ion pumps is not yet complete are the EXVs at X-end 2F and the EXVs at Y-end 1F and 2F.
The switch is scheduled for early next week.
[Takahashi, Hirata, Washimi]
We installed the FLDACCs in the pre-isolator.
| H1 [Ω] | H2 [Ω] | H3[Ω] | |
| 1-6 | 47.3 | 47.2 | 53.0 |
| 2-7 | 55.2 | 55.2 | 62.5 |
| 3-8 | 5.5 | 5.1 | 4.9 |
We also examined the fluctuation of the current from the power supply to the circuit when the PRFPMI was flashing.
A rough diagram of the measurement setup is shown in fig. 1.
We connected three whitening filters (WF1, WF2, and WF3) to the external power supply (TEXIO DC power supply).
Between the +18 V from the power supply and the circuit (WF3), we inserted a 1-Ohm standard resistance to measure the current fluctuation to the circuit.
The data logger measured the voltage difference between the two edges of the resistance.
Figure 2 shows the time series data of the supply current to the circuit, and Figure 3 shows an enlarged view of Figure 2 from 190 to 200 seconds.
The red dashed line shows when we opened the laser shutter on the REFL WFS QPD path.
The green dashed line shows the time when we tuned the CARM/DARM offsets so that the PRFPMI flashes increased.
The current fluctuation becomes larger when the beam hits the QPDs and when the PRFPMI flashes increase.
Since the current spike from the power supply is less than 100 ms (which corresponds to several tens of Hz), the DC power supply must supply not only DC current, but also an AC current of ~1 A to the circuit in total because there are ten or more whitening filters for the REFL PDs/QPDs.
We are unsure whether these values can be supplied by the DC power supply in the computer room, which is far from the DGS rack. However, one possibility of the IR-GR coupling is due to the DC power supply's poor performance at high frequencies.
In any case, we need to discuss how to address the GR-IR coupling issue, as we would require an additional 10 A power supply near the ALS/IOO racks if we were to replace all the WFs for the REFL PDs/QPDs.
We found unused whitening filter (s1909741) was in BS rack. We removed it from the rack and used for the investigation in klog36538. Today, we brought it back to Mozumi circuit room.
Ushiba, Tanaka
## Abstract
Similarly with the PD case in klog36550, We succeeded in solving the couplilng issue when the beam was on REFL QPDs by replacing the power supply.
## What we did
At first, we recovered the shutter for REFL QPDs with the almost same procedure in klog36514. Then, When LSC_LOCK was in FIND_IR_RESONANCES, we opened the shutter so that the reflection beam hit on QPDs. After that, we aligned PRM manually. Figure 1 shows the time series of f DARM error/feedback and PRM guardian state from MISALIGNED_FOR_LOCK_ACQ(2300) to LOCK_ACQUISITION(2000). As PRM alignment got better, DARM signal got noisier. At last, ALS_DARM lock was lost due to the TM actuator saturation. This situation is the almost same as the one in klog31299. So we tried to solve issue by changing the power supply for QPD whitening filters.
Next, we measured DARM spectra in some different situations. Fig. 2 shows the DARM error spectra when IR beam was flushing in FIND_IR_RESONANCES. Blue lines shows the reference when IR flash amount was very low because PRM misalgined and Black lines shows the noisy reference when IR flash amount was very high because PRM aligned. Also, green lines shows the reference of yesterday's last result.
Brown shows the spectrum when the shutter for REFL QPDs was opend but all of QPD whitening filters were turned off. It seems to be the same level as green lines. Therefore, other circuits in the QPD path, ex. IQ demodulaters, did not contaminated the noise to DARM loops.
Magenta shows the spectrum when we turned on the only whitening filter for REFL QPD1 RF17. Then, DARM spectrum got noisy. This is the same situation as the PDA one. So, we changed the power supply to an independent one. Orange line in Fig.2 shows the result after changing the power supply. The noise level got quieter and got the same level as the brown one. This indicates that separating the power supply is valid for reducing the coupling.
Therefore, we need to change the power supplies for all of QPD whitening filters or to modify the current buffer in the circuits. .
This also indicates that we can use REFL QPDs during the lock acquisition term.
## Note
We also examined the fluctuation of the current from the power supply to the circuit when the PRFPMI was flashing.
A rough diagram of the measurement setup is shown in fig. 1.
We connected three whitening filters (WF1, WF2, and WF3) to the external power supply (TEXIO DC power supply).
Between the +18 V from the power supply and the circuit (WF3), we inserted a 1-Ohm standard resistance to measure the current fluctuation to the circuit.
The data logger measured the voltage difference between the two edges of the resistance.
Figure 2 shows the time series data of the supply current to the circuit, and Figure 3 shows an enlarged view of Figure 2 from 190 to 200 seconds.
The red dashed line shows when we opened the laser shutter on the REFL WFS QPD path.
The green dashed line shows the time when we tuned the CARM/DARM offsets so that the PRFPMI flashes increased.
The current fluctuation becomes larger when the beam hits the QPDs and when the PRFPMI flashes increase.
Since the current spike from the power supply is less than 100 ms (which corresponds to several tens of Hz), the DC power supply must supply not only DC current, but also an AC current of ~1 A to the circuit in total because there are ten or more whitening filters for the REFL PDs/QPDs.
We are unsure whether these values can be supplied by the DC power supply in the computer room, which is far from the DGS rack. However, one possibility of the IR-GR coupling is due to the DC power supply's poor performance at high frequencies.
In any case, we need to discuss how to address the GR-IR coupling issue, as we would require an additional 10 A power supply near the ALS/IOO racks if we were to replace all the WFs for the REFL PDs/QPDs.
>Moreover, we found that the REFL HWP before PDA1 and PDA2 was not functioning, so we will restore it.
In this morning, this issue was somehow resolved without any actions.
So, if the similar issue will be found, please let us know.
> Please note that we confirmed that the current drawn from the independent power supply approximately doubled (~1.4 A for +18 V and ~0.8 A for −18 V) after connecting the two boards.
> Correspondingly, the current meter in the computer room showed a reduction of more than 1 A.
Photo. 1 and 2 show the current values on +18 V power supply before and after changing the power supply for the whitening filters. You can see the current reduction before and after the power supply change.
This was a question about the PSL table that was suggested I post here.
Robert Schofield saw the presentation on beam jitter at LVK and wanted to ask if the legs of the PSL table had been grouted. He said he had discussed this with some people from KAGRA a few years ago and wanted to ask if there had been any further discussion about this.
LIGO grouted its PSL during the initial LIGO phase and it reduced PSL table coupling to ground motion. It involves glueing the table legs to the floor with a cement called hydrostone. It can apparently be done without moving the table as you build a dam for the cement around the leg and just pour it in situ.
[Takahashi.R, Washimi, Hirata]
We confirmed that IRM damper works well. After that, we locked suspention again.
1. Release suspention
BF, IRM, IM, RM and TM are released. IP and Topfilter were locked.
2. Check IRM damper position
Fortunately, IRM damper position looks almost same as before releasing suspention.
3. Check motion of IRM damper
First, we tried to check the damper motion, but it seemed that the damper was not working.
Takahashi-san inspected the area outside the SRM rack and found that the cross‑cable used between the feedthrough and the D‑sub cable was not appropriate.
After we replaced the cross‑cable, Takahashi-san confirmed that the IRM damper was working properly using the OSEM signal.
4. Transfer function
Takahashi-san will report later.
5. Lock the suspention
BF, IRM, IM, RM, TM were locked again.
6. Fasten feedthrough flange
We tighten feedthrough flange bolts(K-4-2). 10Nm→15Nm, 2times.
Today's photo is here: https://www.dropbox.com/scl/fo/ljozph0rohm3n46sp2ewj/ACaU31NZxhAETiqBB0v-Ras?rlkey=akuabdr9t2kroq02a5ae85t08&st=wy6asdyg&dl=0
*Sorry, I don't have any information about the relation of the pins and the coil wire-winding directions now. I will ask Takahashi-san.
I have performed an overall test the these check scripts: link
I did not find any issue on the scripts, but there are many issues on the test data.
We need the reconstructed data made by updated offline pipeline.
[Tanaka, Ushiba, Komori]
We successfully mitigated the coupling issue by using the independent power supply to drive two whitening boards for the PDA1, PDA2, and PDA3.
As a continuation of yesterday’s work (klog:36538), we compared the ALS DARM spectrum during IFO flashing under the following configurations.
The results are shown in the attached figure.
Turning on PDA1 (brown):
One of the PDA1 RF outputs was whitened using a whitening board that was already driven by the independent power supply.
The spectrum became slightly noisy above 100 Hz, but it did not become noisy in the 10–100 Hz band, as expected.
Using the conventional cable for PDA3 (magenta):
The spectrum became noisy above 100 Hz, similar to the case with PDA1 turned on, but it did not become noisy in the 10–100 Hz band.
Finally, we measured the spectrum with PDA1, PDA2, and PDA3 all turned on, with the two whitening boards for these PDs powered by the independent power supply (red).
The noise level is close to the noisy reference (black) above 100 Hz, but it remains clearly lower than the reference in the 10–100 Hz band.
In other words, the total RMS is still smaller.
In fact, the DARM, MICH, and PRCL signals appeared to become quieter during arm flashing with the PRMI locked.
Please note that we confirmed that the current drawn from the independent power supply approximately doubled (~1.4 A for +18 V and ~0.8 A for −18 V) after connecting the two boards.
Correspondingly, the current meter in the computer room showed a reduction of more than 1 A.
In addition, after these modifications, we found that the dark offsets for PRCL and MICH had changed, likely due to the change in the power supply.
Therefore, we performed a dark offset compensation.
Tomorrow, we will check the stability after opening the shutter in front of the REFL QPDs.
If the IFO is not stable, we will power one of the QPD whitening boards with the independent power supply and check the stability again.
Moreover, we found that the REFL HWP before PDA1 and PDA2 was not functioning, so we will restore it.
> Please note that we confirmed that the current drawn from the independent power supply approximately doubled (~1.4 A for +18 V and ~0.8 A for −18 V) after connecting the two boards.
> Correspondingly, the current meter in the computer room showed a reduction of more than 1 A.
Photo. 1 and 2 show the current values on +18 V power supply before and after changing the power supply for the whitening filters. You can see the current reduction before and after the power supply change.
>Moreover, we found that the REFL HWP before PDA1 and PDA2 was not functioning, so we will restore it.
In this morning, this issue was somehow resolved without any actions.
So, if the similar issue will be found, please let us know.
During the migration work of k1script, I found a plot range of finesse plot on the web was broken as shown in Fig.1.
It came from a change in the format of a history of finesse values.
I'm not sure when this change was made, anyway, an unknown header line had been added to the beginning of the file.
For now, I've modified the plot code to properly handle header rows.
Note that the character used to indicate comment lines varies by language and plotting tool.
So this is just an ad-hoc fix.
