Thank you for checking the model, Ushiba-san.

I completed editing the model for WFSf3.
The used models are followed. These were successfully compiled in k1ASC and k1psliss. Next we will do "make install".

• The RFQPD RF signal of RFQPDs: k1psliss-->[Dolthin]--> k1ASC
• The RFQPD DC signal of RFQPDs: k1psliss-->[Dolthin]--> k1ASC
• The actuator signal to PZT for DC centering loop: k1ASC-->[Dolthin]--> k1psliss

[Kimura]

A gate valve was opened between the Y-arm duct and the new pressure sensor to connect the pressure sensor to the Y-arm duct.
The attached photo 1 shows the pressure change before the gate valve was opened and photo 2 shows the pressure change after the gate valve was opened.
After connecting the pressure sensor, a blank flange was attached to the angle valve for evacuation to protect against misoperation.

This operation operated the minimum required sensor to detect pressure faults in the X- and Y-arm ducts.
In the future, similar sensors (k-log 29326) will be operated on the end side of the X- and Y-arm ducts.

Yokozawa, Ushiba, Takano

Summary

We found a mysterious peak at 28MHz in the demodulation singals. From the measurement with varied conditions, finally we conclude that this peak comes from GrPDHY servo and is coupled to other signals via crosstalk. We will replace the servo with a spare and try the measurement again.

Detail

Continued from klog 29146.

Today we checked the signal around GrPDH in high frequencies.

1. Measurement of demodulated signal

First, we measured the demodulator output for GRX. To increase the signal to noise ratio, we used the PDHX servo's first gain stage. Before the servo an RF LPF and 10dB attenuator were connected. The output of the demodulator was connected to GrPDHX servo and the gain of the first stage was set to 31dB, then OUT2 of the servo was connected to a Moku:Lab. Then, we found that at 28 MHz there was a large peak even though the signal got through the LPF. The spectrum is shown in Figure1.

2. Tuning off the oscillators

As the source of the peak, we suspected the local oscillators, such as for GR PDH, PLL, IR sidebands, etc.. First we turned off the LO for GR PDHX, at 33MHz, but nothing changed. Next we turned off the seed LO of f1 and f2 sideband, 5.6MHz, but no effect again. Therefore, we considered that this peak is not from LOs but other circuits.

3. Changing the condition

Next, we stopped to use the servo and measured the demodulated signal without amplification, then the peak still appeared. With this condition, we touched the cable, then noticed that the peak height varied with the distance from GrPDHY servo. This implies that the peak is coulpled to the demodulated signal by radiation from GrPDHY servo.

4. Measurement of the signal from GRX RFPD

We measured the signal from GRX RFPD directly, and we found a broad peak around 33 MHz. Even though turning off the LO of PDHX, this peak existed. This peak ssems to come from the resonant peak of the RFPD. We also touched the SMA cable from GRX RFPD, and noticed that the 28 MHz peak appeared when the cable is close to the PDHY servo.

5. Turning off the power of GrPDHY servo

We turned off the power of GrPDHY servo, and checked whether the 28MHz peak changes or not. Then, we found that the peak dissapeared after turning off the servo. Therefore, we were confident that the peak is generated inside the GrPDHY servo and coupled to the signals around it.

6. Measurement of the signal from GRY RFPD

Next, we measured the signal from GRY RFPD directly, and similarly we found a broad peak around 34 MHz, which is the resonant peak of GRY RFPD. We also put the SMA cable from GRY RFPD close to the GrPDHY servo, and confirmed that the 28 MHz peak appeared as shown in Figure2.

7. Turning off the power of GrPDHX servo and GrPDHY

We checked the effect of GrPDHX. We put the SMA cable close to GrPDHY servo, and turned off the power of GrPDHX servo. However, the 28MHz peak was still there. Finally, we turned off the power of GrPDHY servo, and checked that the peak dissapeared after turning off the servo as shown in Figure3. After turning on the power, the peak appeared again.

Conclusion

From these measurement, we concluded that GrPDHY servo generates and radiates a sharp peak noise at 28MHz, and the noise couples to the signal arpund the servo by crosstalk with cables. The previous measurement klog 29424 reported that the input refferred noise of GrPHDY is larger than that of GrPDHX, and this result supports our consideration.

Next

Fortunately we have a spare of the servo. We will replace the servo with the spare and check whether the 28MHz peak disappear or not.

[Takahashi, Ikeda, Hirata]

We investigated the small horizontal actuation problem in the BF damper. Particularly, the efficiency of the H1 actuator was too small (2um/1000count). We checked the following points.

1. Resistance and inductance of the primary and secondary coils: They were normal.
2. Cabling around the H1 coils: There was a small change in the LVDT signal by touching the connection points.
3. Coil driver and LVDT combiner: The efficiency of the H1 coil was still small by swapping the channels of H1 and H2.

Finally, we found that a cable at the Dsub connector on the BF side plate was touching the bracket for the secondary coils of the H1 LVDT. The cable was treated to keep a gap from the bracket. When the cable was released from touching, the BF rotated much in yaw. We offloaded the BF with the F0 yaw FR.

I checked ITMY and found that almost all GAS filters were low by seravera hundreds of um.
Figure 1 shows the time series of GAS motion when I requested ISOLATED state.
When moving F1 and F2 up, F0 and BF go down once: this implies that suspension is touching at payload.
So, it is very likely that the payload is now sit on the installation flame (or EQ stops) if there is no control.

Figure 2 shows the TF of BFY when ITMY is in TWR_FLOAT state, which keep the suspension height close to the nominal position.
As you can see, resonant frequency is around 30 mHz ad TF seems healthy, so the problem seems GAS filter position.

Since it is not good situation that the suspension is sitting on the installation flame, I kept ITMY in TWR_FLOAT state to avoid it.
So, please keep current guardian state until GAS offload will be performed.

I made a water absorber tool between foot bellows and poles inside them at EYA. The thin red tube whose inner diameter is ~2mm should be inserted between the foot bellows and poles inside them. Anyway, this tool can absorb water effectively. The red plastic tube will be changed by a stainless tube.

Yesterday I started measuring the TFs at the IP stage. The results were strange: the first resonant mode was different from the previous measurements. Along L, the IP mode is about 70 mHz (see Pic 1 and Pic 3) but has a low Q value, while along T the resonance is shifted from 70 mHz to 100 mHz (Pic.2and Pic 4).
To check if the IP was rubbing or softly touching inside the chamber and to verify if it could move in different positions along L and T, Today I moved it by adding an offset on the coils (L,T) which corresponded to a displacement of about 400 mum.
Pic 3 and Pic 4 show the TFs along L and T. The resonances are still there. The Y TF is the same as before (see Pic. 5).
After this test, I measured the transfer functions of the vertical stages and compared them with those from 26 April. The vertical TFs are different from the previous ones. The F0 TF (Pic. 6), F1 TF (Pic. 7), F2 TF (Pic. 8) and F3 TF (Pic. 9) don't show a peak at 133 mHz and all other modes look shifted. The BF GAS TF (Pic. 10) also is different. The BF_L TF and BF_T TF show similar behaviour to the IP stage. Along L, the first pendula mode is at 66 mHz with a low Q value ( (see Pic 11). Along T, the mode is shifted from 66 mHz to 100 mHz with low DC gain (see Pic 12).  BF_Y TF shows a shifted resonance from 0.031 mHz to 0.041 mHz and a lower DC gain (see Pic 13).
It's unclear what's going on. Maybe some stages are rubbing or touching somewhere inside the chamber?
 

[Hirata, Ushiba]

Abstract:

We checked the input alignment and confirmed it seemed healthy.
After that, we centered POP FORWARD QPDs and closed GV between PRM and PR3.

Detail:

First, we aligned XARM with almost the same procedure written in klog29346 (since GRX lock is somehow not so stable, PR3 is manually aligned instead of GRX ADS).
Then, we checked the beam spot in front of PR2 (fig1: IR, fig2:GR): looks good.

After that, we centered POP forward QPDs (fig3).
Then, we closed GV between PRM nd PR3 and checked POP FORWARD QPDs again (fig4).
Only QPD2 pitch value was changed from 0.
Since amount of the change is not so large and final condition should be the same as before closing the GV, we didn't move QPDs after GV close.

I checked PRM "SF GAS" LVDT cable resistance and inductance at the feedthrough flange with flip cable (flange port No.3-6). According to the klog:28586, this in-vac cable connector was unstable and fixed. So we measured it.

No ground fault and no interconnection between each pins.
 

Hirata-san, Yokozawa-san, R.Takahashi-san, Ikeda

We set up workstations in the PR booth.
LAN and power supply are not yet connected.
Will be connected next time.

The network cable connector claw seems not to be properly fixed in the GigE cam even if I tried to push the connector to the GigE cam. So I attached an additional short network cable with the extension connector as the attached photo. In this case, the connector claw could be fixed properly. After that, I confirmed the PMC trans image could be displayed.

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.