The water for the chiller was replaced from distilled water to tap water.

The image of PMC trans was lost maybe because of the disconnection of the network cable that had no claw in the Gige cam. I will check in this afternoon. 

Date: 5/9

I checked the beam position again.

Pcal beam position change (between 5/8 and 5/9)

• The Tcam direction seems to have changed by 0.5-1mm, but the reason is not clear.
• Additionally, the Pcal beam positions appear to have changed from yesterday (5/8) by approximately 3mm.

We need to continue monitoring them.

I checked the TF measured in air. The results were consistent with the last measurement in vacuum. The Q of the GAS filters seems smaller than the last measurement (The script for the BF GAS was not working). The TF of the IM H3 OSEM, in which the flap was rotated more than 40°, is consistent with the reference.

[Ikeda, Takahashi]

We checked the resistance and inductance of the LVDT coils for the BF damper at the feedthrough flange with the flip cable.

[Ikeda, Takahashi]

We checked the resistance and inductance of the LVDT coils for the BF damper at the feedthrough flange with the flip cable.

[Ikeda, Takahashi]

We checked the resistance and inductance of the LVDT coils for the BF damper at the feedthrough flange with the flip cable.

We forgot to include the first gain stage of the common mode servo. The spectra in terms of the input of the servo are actually shown in the attached figure.

Note that the servo for PDHX and PDHY have different values at the first gain stage, +9 dB for PDHX and -9 dB for PDHY. Therefore, the gain for PDHX is about 8 times larger than PDHY. For this reason, the situation is reverted from the previous post; PDHY is noisier than PDHX.

Now it seems that for PDHY peaks seen in PDHX is smeared by the floor noise with weird frequency dependence except for the peak around 20 kHz.

I checked and took pictures of earthquakestops for PR2 payload.

I uploaded those pictures to KAGRA Dropbox here.

I checked and took pictures of earthquakestops for PR3 payload.

I uploaded today's pictures to KAGRA Dropbox here.

[Tanaka, Miyoki, Takase]

Summary

We recovered the BD chiller water circulation. So the FB output was set at the default current of 27.8A(~18W).

What we did

Firstly, we tried the water flow check of the Adjuster BD solely. We confirmed that the water flow is enough.

Secondly, we attached the the yellow tube to the chiller return and the transparent tubes from the PMC BD on the Adjuster BD in the space above the edge of the optical table after turn off the FB amp part (So the IR power was tiny round PMC). Then we put the Adjuster BD in the water basket and checked the water flow by operating the chiller. We confirmed the water flow in the all water paths and BDs. Actually, we sensed the BD temperature was cool by fingers.

The chiller was stopped again.

Thirdly, we replaced the 30W detectable power meter head with the recovered Adjuster BD. In this process, we found that the water tubes interfered with the PEM mike that was suspended from the metal mesh. So we pulled up the mike about 30cm to avoid interference. After that we also replaced the 50W detectable power meter with the original PMC BD at the rough position. Then we turned on the FB and got ~ 1W laser power. We realocated the PMC BD to have the beam be at the center. After that, PMC was locked, and we djusted the Adjuster BD height to introduce it at the center of the Adjuster BD. We also confirmed that the temperature of the PMC/Adjuster BD around was 20C by using the non-contacting type thermometer.

We restarted the chiller.

Fourthly, we increased the current of the FB upto 27.8A (~ 18W). If there was no water circulation, the temperature of the Adjuster BD became ~40C degrees when the FB output was 10W with in 30 minutes or so. After the recovery the chiller path for BDs, the temps of the Adjuster/PMC BDs were 21C just after the FB laser operation. After ~40minutes later, we checked the temps again, and got ~22C. So we recognized that the water  chiller system was working well.

Please Kimura-san ask somebody to fix it.

During the EY photosensor work, we found there is leakage of the air for clean booth at the connection port.
Attachment is a movie around the leakage point.

Yesterday 9:45, Hayakawa-san stopped the Y2300 water pump.

[Tamaki, Ushiba]

We measured resistance, forward voltage, and inductance of the newly installed photosensor/actuator cables from the feedthrough flange at EYV.
All measured values are consistent with those during health check before O4a and seem fine.
Following table shows the summary of the measurement (with the values before O4a).

Also, we measured the resistance of all the other connections like 1-2, 1-3, and so on.
All values are OL, so we confirmed there is no unexpected short among the new cables.

Date: 2024/5/8

I checked Pcal-X beam positions on ETMX with the suspension-aligned state.

Positions comparing to the results 25th Apr when we had the last beam alignment work:

I believed that a change of this magnitude could be adjusted by Picos, but today I leave it as is and monitor it. 

Ushiba, Tanaka, Takano

Abstract

We started to investigate the source of the strange coupling of ALS signal and IR REFL. We checked the slow DAQ of GrPDH of each arm with the shutter closed. We found that GrPDHX signal is noisier than GrPDHY above ~20 Hz, with many peaks and white noise floor,

and nonstationary peaks above 7 kHz were seen for both PDH signals.

Detail

For years we have suffered from the mysterious coupling between ALS signal and IR signal (ref: 11411). It might be due to a GND loop around REFL/POP/POS area and could be coupled to DARM sensitivity. To solve this issue once for all we started to investigate the source of this coupling.

First we suspected that some electronics for GrPDH might oscillate at some high frequency. To check the behaviour in high frequencies, we monitored the spectra of GrPDH slow DAQ, not at 16 kHz but at 64 kHz. Figure1 shows the spectra of GrPDHX and GrPDHY in terms of the input equivalent noise of the common mode servo. The spectra labelled noX are the measurements taken in different time and REF are the spectra with the input of the servo open electrically. It is certain that above 20 Hz the ADC noise is below the signal from the RFPD.

From these measurements we found these characteristics;

• For GrPDHX the floor level is almost flat above 20 Hz, 6e-7 V/√Hz, whereas the floor level of GrPDHY has some weird frequency dependence. At 100 Hz GrPDHX is about two times larger than GrPDHY.
• For GrPDHX many peaks are seen, at 60, 120, 180, 240, 300, 480 (power line), 68, 136, 234, 260 (mysterious) Hz.
• For both spectra, many peaks are found above 7 kHz. The center frequency of these peaks also changes in time (measurement no2 was taken 5 min after no1 measurement).

Anyway, it seems that the condition of GrPDHX is worse than GrPDHY.

Next

We will check the spectra of the related electronics one by one in high frequencies. Especially, we are interested in

• The original RF signal from RFPDs
• The demodulated signal above 32 kHz to check whether RFPDs are oscilating or not

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.