I applied current to the IM heater on IX payload because it reached 38K.

The voltage was 7.0 V.

Aso, Komori, Tanaka

## Abstract

We scanned MN by applying the DC offset in OPTICALIGN from 800 to -3600 cnts in yaw and from -1700 to 1000 cnts in pit after removing the resisters on MN coil drivers to release ITMX. However, the situattion seems not to be changed, unfortunately. We try to scan it in the other region (over 800 in Yaw?) tomorrow.

## What we did

First, we removed the resistor between MN coil drivers and MN coils to increase the range in the SAFE state of ITMX. Then, we changed the state from SAFE to ISOLATED and turned off the comp gain filters in FM9 of MN_COILOUTF.

Then, we performed the centering of TM TILT OPLEV QPD by changing the setpoint of BF DC control in Yaw direction and by moving the moving mass in PIT direction. This time, the moving mass labeld PITCH_AR seems not to be responded, also the mass labeled PITCH_HR seems to be responded only the negative direction. Fortunately, the direction was the same as which direction we want to move. So we moved the mass labeled PITCH_HR to centering. (We don't confirm that whether the mass was at the edge of the range in the positive direction.)

After that, we performed the centering of MN TILT OPLEV QPD by moving the stage manually. Fig. 1 and Fig. 2 show the value of the micrometer in PIT and Yaw before centering, respectively.

Next, we moved MN in negative Yaw direction by applying DC offset in OPTICALIGN and checked the PIT/YAW couplling in MN and TM oplev changed or not. We applied the DC offset by 200 cnts. Whenever the TM oplev beam was out of the range, we centered the QPD by adjusting the setpoint of BF DC control or by moving the moving mass. Whenever the MN oplev beam was out of the range, we centered the QPD manually. At last we moved MN from 800 cnts to -3600 cnts in terms of OPTICALIGN, but the situation seems not to be changed. 

We performed the similar trial for PIT. In this time, MN and TM Yaw were at each edge of each QPD. In this state, we scanned OPTICALIGN from -2000 to 1000. However, the situation also seems not to be changed.  

During these trial, we found there seems to be hysterisis.

Fig.3 and Fig. 4 are ones after the trial in PIT and YAW, respectively.

We try to scan it in the other region (over 800 in Yaw?) tomorrow.

Abstract

In the calibration rehearsal (klog#33609), we had ~11% inconsistency on the actuator efficiency ratio of PRM and BS from the past measurement (klog#30091).
We haven't done follow-up measurements for this issue yet. (We can resume it after coming back to MICH.)
Because our result also have inconsistency with the feedforward gain for MICH2PRCL (klog#33695), I checked past measurement to decide feedforward gain.
Then, I found a possibility that current MICH2PRCL gain is biased as 10-15% by the effect of a suppression by PRCL OLTF.
 

Details

According to the filter name of FM9 on K1:LSC-MICHFF2, feedforward gain is based on the measurement results on Dec. 26th, 2023 (klog#28094) and related measurement files are /users/Commissioning/data/MICH/2023/1226/TF_MICH2DARM_MICHFFOFF_20231226.xml for MICH2PRCL and /users/Commissioning/data/PRCL/2023/1226/TF_PRCL2DARM_MICHFFon_PRCLFFoff_20231226.xml for PRCLout2PRCL.

All MICH related test points are the out-of-loop channel of the PRCL loop. On the other hand, there is no out-of-loop channel at the downstream of the feedback point in the measurement file of PRCL. So the feed-forward gain seemed to be computed as
(PRCL_IN1/PRCL_OUT) / (PRCL_IN1/MICH_OUT) = A_prm / A_bs * (1 + G_prcl).

Though I tried to find measured OLTF around 2023/12/26, there was no measurement during 3 months before and after. So I tried to reproduce PRCL OLTF from error and feedback signals just after the measurement on that day. As shown in Fig.1, estimated UGF is ~13Hz. Open loop suppression by this OLTF is shown in Fig.2 and we can see suppression effect can be ignore above ~100Hz. On the other hand, measurements for FF were done with 50-200Hz. Blue, red, and green curves in Fig.3 represent a TF from PRCLout to PRCL, from MICHout to PRCL w/o G_prcl correction, and from MICHout to PRCL w/ G_prcl correction.

Actuator efficiency ratio by these TFs are also shown in Fig.4 and there is ~13% difference in the estimated results between without (~24.5) and with (~27.9) correcting G_prcl suppression. A result with correction of G_prcl suppression is consistent with the results of calibration measurement in klog#33609 (~27.2). And also, current FF gain in MICHFF2 (corresponds to ~25.7) is close to a result without a correction of G_prcl suppression. So current FF gain for MICH2PRCL may have a ~13% bias (though it might not be so serious from the view point of IFO lock).

Because an estimation in this post is based on the reproduced OLTF, it's difficult to believe values in this post. But this result suggest that it's better to validate a feedforward gain by multiple measurements. In addition for same measurements which will be done in future, G_prcl suppression will not be a negligible because PRCL UGF is increased in klog#33437 and klog#33627.

With Shingo Hido

We performed the integrating sphere calibration for Pcal-X.
The results are attached (PDF file).

Based on these results, we recalculated the relevant online parameters and updated them accordingly.
The updated EPICS channel values are summarized below (rounded to four significant figures):

Notes

• There were no significant changes in the RxPD or TxPD values.
• The background (BG) values were updated using only today's measurements. The previous values were based on averages over multiple past measurements. This update avoids the influence of older values that were set using different methods (see klog33465).
• We also started updating K1:CAL-PCAL_EX_2_INJ_V_GAIN, a parameter used to equalize the injected sine wave amplitudes from path 1 and path 2 at the ETM. This parameter had not been updated for a while.
• Prior to this Pcal-X calibration, we performed a beam position check using the Tcam. Starting from this update, we have begun reflecting the measured beam positions in the corresponding online parameters.

As a reference, we performed the same procedure on the IY cryopayload.
The result is shown in the attached figure.

The response ratio between the MN and TM in IY is approximately 1.2, compared to 1.6 in the IX case.
Additionally, the response in IY is quite linear and reproducible, and the response amplitude is significantly larger than that observed in IX.

[Yokozawa, Aso, Komori]

Abstract:

The point of contact may be located around the IM or TM, rather than the MN, based on the measurement that the DC response of the TM pitch is smaller than that of the MN.

Detail:

We attempted to identify the point of contact in the IX cryopayload.

First, we performed a rough centering of the beam spot on both the MN and TM QPDs by adjusting the moving mass on IX MN.
At that time, the oplev pitch signals in the unit of error function were approximately –0.3 and –0.2 for the MN and TM, respectively.
Since the MN yaw error signal was 0.997 and we do not have a system like the moving mass to adjust the yaw degree of freedom, we could not perform the same thing in yaw unless we relocate the MN QPD inside the tunnel.

Next, we applied several offsets to the MN optic alignment, ranging from –300 to +300 in steps of 100, and measured the resulting oplev values for both the MN and TM, as shown in the attached figure.
The MN response was consistently larger than the TM response, suggesting that the point of contact is around the IM or TM.

It should be noted that the responses were not linear (larger positive offsets resulted in larger DC responses), and the oplev values themselves were not reproducible.
However, the trend—namely, that the MN response was always larger—was reproducible.

IX IM Temperature is near 40 K, It is better to turn on the heater. Although ~ 10.5V is selected for IY and EX, the lower value is suitable because IX Im cooling speed is slower than IY and EX.

The bump-like temperature changes in MTR, IMR, and MIR were caused by the temp changes in the 4K REF2 4K HEAD temp around 20 K. 

I checked the MN, TM, PF OPLEV TILT VER and HOR. PF/MN/TM OPLEV TILF HOR (not VER) seemed to show strange jumps around -7 days. Around -5.5 days, all OPLEV showed jumps and spike noises. 

[Komori, Yokozawa, Ushiba]

Abstract:

ITMX TM chain seems to touch RM chain (we suspected IM-IRM).
Hitting becomes better when MN was tilted in -YAW/-PITCH direction (however, it cannot be released with the current actuator efficiency), so it would be good to confirm if we can release it with original AE with high power coil driver.

Detail:

Since health check results were not good and it is very likely that suspension is touching/rubbing somewhere, we started from confirming touching position.
First, we added offsets from F2 GAS filters at TWR_FLOAT state and checked the reaction of the other GAS filters.
If the suspension is touching with the flame below F2 GAS filters, not only F2 GAS filter but also the other GAS filters changes their DC position due to the change of the load.
Figure 1 shows the result and DC position doesn't seem to be changed except for F2 GAS filter, so suspension doesn't seem to touch security flame.
So, the reason of the strange suspension TF is very likely come from the touching/rubbing between main chain and RM chain.

Then, to confirm the touching place precisely, we moved suspension in pitch direction and sudden large jump was observed when moving in -pitch direction (fig2).
This implies that suspension is rubbing between TM chain (TM, IM, and MN) and RM chain (RM, IRM, and MNR).
After confirming somewhere in the payload is rubbing, we performed visual inspection of the payload from the viewport for MN OpLev but no information can be obtained due to very narrow field of view.

After that, we checked which direction is good for the payload by monitoring the actuator efficiency of pitch with various yaw offset.
Figure 3 and 4 are one of examples of OpLev signals when adding some offsets.
In both cases, pitch offset was changed by 1500 cnts but TM motions are about 35 and 50 urad in the case of fig3 and fig4, respectively.
So, yaw negative direction and/or pitch negative direction seems to be better in terms of the suspension motions at DC.

For further detailed check, it would be nice to remove the resistance from the actuators to increase the AE and scan various offset of roll/pitch/yaw to confirm if suspensions can be released with some combination of these offsets.

If some contacts happened in the IX cryo-payload, the sudden temperature changes could be expected in these components because it had thermal contact.

Fig 1 shows the temp trends after reporting the strange drift on 8th May.

Around 4 days before (8th may), slight temperature changes happened in MTR. The changes about -2.4 days and -1 day happened in MTR and IMR. 

By the way, the operation of the moving mass would generate slight heat and heat up  MN??

The water level of the chiller for the main IR laser became very low (just above the minimum level) since I added 1L of water on March 29. So we (the mine staff and I) added water.

Meanwhile, overflow happened because of too rapid a refill, and the chiller stopped in a short time(~1min). I checked the laser and the temperature of the laser, and fortunately, the laser had not stopped.

The total added water was about 2L to reach the middle level, but the 2L sounds too much. I checked water leakage carefully around the chiller and in the PSL room, and I could not find anything wrong.

It seems to be OK right now, and we left it as usual.

A weekly check of the water level every Friday will be performed by the mine staff from this week. If they find something wrong, it will be reported to me.

I increased the voltage from 10.5V to 10.6V because the temp started decreasing again.

In the previous measurement of the MN stage, the measurement at 46.21 Hz failed, so I recreated the frequency list and updated the templates.
The script to generate the frequency list is located at `/users/shingo/CAL/line_freq/cal_line_s.py`.(detailed document in JGW-G16675) 

Forgot to mention: nice to re-adjust the input alignment to PMC at some point.

>Anyway, H2O frosting on the AR side at this time is expected to be less than the case on Aug 12th, 2023. Also, we can expect the EX 50K REFBRT HEAD temp will reach ~80K for 10 days, assuming the same performance as the case on Aug 12th, 2023.

The EX 50K REFBRT HEAD temp is around 90K, which is higher by 10 K compared with the incident on August 12th, 2023. Please come back! Because of this higher temperature, the BRT2 temp cannot be below the critical temp.

It might be effective to recover the cooling power by replacing the flexure tubes again with those that were sent back to Sumitomo Heavy Industry for its gas components inspection after cleaning their inside and refill He gas in them again. 

The present IM temps. IX temperature finally increased its cooling speed. On the other hand, the EY temperature is slowly cooling because of one cryocooler operation for the cryo-payload.

I adjusted the voltage to around 10.5V to find the equilibrium temperature state in this morning. Then the present temp is fluctuating around 40K.

I adjusted the voltage to around 10.5V to find the equilibrium temperature state in this morning. Then the present temp is fluctuating around 35 K.