[Dan, Fujimoto, Tanaka, Takano]

Summary

After adjusting SRM yaw, we successfully implemented the SRCL control with POP f1 signal. Currently the UGF is ~ 18 Hz. Also, SRM ADS worked with AS DC power.

Detail

After the PRM alignment (and the QPD centring work, which was found to be a failure later, though), we tried to close the SRCL control loop. Looking at several RF signals, we decided to use POP f1 I signal, which seemed to have a decent SNR. We copied all the filter banks from PRCL1 and PRCL2 and implemented them into SRCL1 and SRCL2. After tweaking the gain in SRCL2, SRY was stably locked with the setting below:

• SRCL1: FM9 (pole: 0 Hz, zero: 8 Hz)
• SRCL2: FM6 (an elliptic low pass with a cutoff at 300 Hz)
• Gain: -800

With these filter bank settings, the open loop gain was measured as shown in Fig. 1. The UGF was ~ 18 Hz, and the phase margin was 43°.

Following the success of the SRCL control, we implemented a dithering control loop to improve SRM alignment. The dithered frequencies were 4.3 Hz for SRM pitch and 6.3 Hz for SRM yaw, and we demodulated the AS_PDA1_DC signal. The demodulation phase was set as shown in Fig. 2; I set it to 8° for pitch and 13° for yaw. The loops were closed with the gain of -1000 for both pitch and yaw control.

Even though the alignment was improved by SRM ADS, the intracavity buildup was only 1.5, which should be ~ 7, considering the BS and SRM transmission. It was also found that the REFL power increased when SRY was locked, which should be decreased. It might be that we locked SRY to higher-order modes, but judging from the camera images at AS and POP Spol, the fundamental mode appeared to be on resonance. Yesterday, we confirmed that the buildup factor for PRY was ~7, close to the expected value, so the birefringence loss does not seem to limit amplification. We need more information to investigate the reason.

[Dan, Takano, Tanaka, Fujimoto]

Summary

From the previous SRC flash searches, it was found that a large yaw offset of the SRM is required to observe SRC flashes. Under such conditions, the SRM OPLEV beam went out of range of the QPD.
To address this issue, we performed centering of the OPLEV QPDs (TILT QPD and LEN QPD) for the aligned SRM.
Although the centering onto the QPDs were confirmed while we were in the mine, after returning to the control room we found that the beam was no longer incident on the TILT QPD. We plan to check the situation and recover the alignment tomorrow.

What we did

After obtaining a reasonable SRM alignment during the SRC flash search in the morning (klog #36876), we carried out the SRM OPLEV centering work in the mine in the afternoon.
Inspection around the QPD revealed that the beam was clipping on the holder of the first steering mirror. Therefore, we decided that rearrangement of all the optics, including the steering mirror, BS, TILT QPD, lens, folding mirror, and LEN QPD, was necessary.

First, we adjusted the position of the first steering mirror and aligned the beam onto the TILT QPD. After coarse alignment, fine adjustment was performed using the micrometer stage of the QPD while monitoring the QPD signals.

Next, alignment onto the LEN QPD was performed. For the LEN QPD, the distance relationships between the SRM and lens, and between the lens and LEN QPD, are important. Therefore, the downstream optics (BS, lens, folding mirror, and LEN QPD) were repositioned and aligned so that these distances matched the previous setup (klog #7952).

Fig. 1 shows a photograph of the final layout. The distances between optics are as follows:

• TM to upper viewport: 990 mm (assumed to be the same as the previous setup)

• Viewport to first steering mirror: 305 mm

• First steering mirror to BS: 40 mm

• BS to lens: 45 mm

• Lens to folding mirror: 110 mm

• Folding mirror to LEN QPD: 273 mm

After repositioning, final centering onto the QPD was performed using the micrometer stages of the QPD.

After the adjustment, the optical table was covered with aluminum foil, and we returned to the control room. At that point, we noticed that the beam was no longer incident on the TILT QPD. It is possible that the aluminum foil blocked the beam path or disturbed the alignment during covering. We plan to check the situation tomorrow and recover the alignment.

I checked the behavior of the OSEM gains when the Type-B/Bp chambers were evacuated in June, 2024. The gains of some OSEMs in any IMs (PRM, PR2, PR3, BS, SRM, SR2, SR3) were reduced in vacuum.

Takano, Fujimoto, Tanaka, Dan

Summary

We performed the initial alignment of the IFO by following the procedure in klog36759. After that, we tried to find the SRC flash by shaking SRM and moving SRM IP in yaw direction. Finally, we observed clear SRC flashes.

What we did

Initial alignment of IFO

First, we performed the initial alignment of the IFO. Since the transmissivity of SRM was changed, the usual initial alignment procedure cannot be used for the AS side alignment. Therefore, we adjusted the alignment by referring to klog36759.

For X-arm and Y-arm, we used the usual initial alignment procedure. After that, we continued the alignment according to the procedure described in klog36759. As written in the klog, we moved OMMT1 while monitoring OMMT1_TRAS_QPD1. When the beam position on OMMT1_TRAS_QPD1 became almost centered, we regarded the AS side alignment as good.

Search for SRC flash

Next, we tried to find the SRC flash by adjusting the alignment of SRM. We set only ITMY to LOCK_ACQUISITION and misaligned the other Type-A suspensions. We also restored the SRM IM OPTICALIGN pitch value to yesterday’s value of 3825. In this condition, we largely moved only the yaw alignment of SRM. We used the stepping motor and moved SRM IP F0_Y from about -12073 to -27073. Then the flash could be seen. After that, we continued the alignment while monitoring the flash signal. Finally, we found good SRC flashes with the following SRM IM OPTICALIGN values:

• P: 3900
• Y: 480

The flash signal was monitored with K1:LSC-POS_PPOL_DC_OUT_DQ. This is the signal from the temporary PD installed yesterday on the POS table, and the flash appeared clearly in this channel.

However, since the suspension was still oscillating, it was difficult to further optimize the alignment at this moment.

Next, we entered the mine, center the QPDs, and try to turn on the local controls.

This foton error occurred because a filter bank block with one or more filter modules defined was removed from the model.
It was fixed by removing filter module definition of the removed filter bank block manually.

-----
In such case, "File errors" is displayed on a red background, and the error details pop up in a separate window when foton is opened as shown in Fig.1. In many cases, this type of error occurs when a filter bank is removed from the model while its filter design remains. This is because, when the model is rebuilt after deleting a filter bank block, the module name definitions at the top of the foton file are generated based on the new filter bank list, but the filter coefficient definitions are not cleaned up. Normally, this specification should not become a problem, because filter bank blocks are not repeatedly added or removed without sufficient consideration and reviews. But it often becomes an issue within KAGRA’s management and operation framework.

Anyway, VIS-SRM_TM_SENSCORR_L was removed from the k1vissrmp model probably in klog#36457 though some filter module definition was remained on that filter bank. An only safe method is to clean up the filter modules on the filter bank that will be deleted before installing the updated model. But in this case, nobody probably noticed fact that some filter banks would be removed because it's not mentioned in the model update plan (klog#36374). The other method is to edit the foton file manually after installing the updated model. Though foton files are in plain text format, their formatting is so strict and they can very easily become unreadable from foton or models by a manual edit. So it's never recommended. But this is only way if we couldn't notice before installing updated models and I did it in this time. Removed filter modules are shown in Fig.2.

After manual fixing, all errors were cleared on foton. But a warning still remains related to the too low (but non-zero) zero/pole as shown in Fig.3. Though it's not a problem on reading filters by foton and models, numerical errors often occurs on that filter bank. Please remove it if it's unnecessary, or please change corner frequency as a higher value with a careful design of the control if it's used.

Dan, Takano, Fujimoto, Saito, Tanaka

## Abstract

We tried to find the SRC flash by moving alignment SRM. Yaw alignment seems to be larger than the range of IM actuator. We observed SRC flash after moving SRM and SR3.

## What we did

This morning, we tried find the resonancre in SRC by moving the alignment of SRM largely in both P and Y directions. Unfortunately, SRM DC control seems not work well. So we stopped the any DC controls of payload parts, and we decided to use OPTICALIGN to move alignments. This time, we aligned ITMY and misaligned other Type-As, that is, we made up SRY cavity. Moreover, we increased IMC power up to 10 W. We used awggui and set the excitation amplitude ~1000 cnts and the frequnecy 0.05 Hz in Yaw and 0.04 Hz in Pit, respectively. In this parameters, SRM alignments moved largely enough TM oplev gots out of ranges. However, any flash could not be observed in AS RF34 IQ signals and DC power in AS PDs. Therefore, we put the additional PD at the POS table to observe the flash.

This afternoon, we entered the mine and installed the additional PD just after the 2 inch lens in main IR beam path on POS table. Also, we used the POS PPOL PD channel (K1:LSC-POS_PPOL_DC) for this PD tempolarly. After that, we tried again. However, any flash could not be observed. We used TCam to find the beam spot reflected SRM on ITMY. 

Then, we increased Yaw scan amlitude to ~5000 cnts, which is the almost maximum. Then, Saito-kun found that the scattering at the edge of the TCam image.So we adjusted the actuator output when we observed the scattered light. Then, we oscllated the SRM only in Yaw direction. During the oscillation, we adjusted PItch by applying the DC offset with monitoring TCam image. After adjusting, the scattered light could be observed in the edge of both ITMY and ITMX TCam images once per 20 seconds. This duration seems to be consistent with the Yaw excitaition frequency. Therefore, the beam reflected from SRM seems to be shifted largely in Yaw direction. The shift amounts seems to be larger than the IM actuator range. So, it is necessary to use IP to move SRM more largely.

This time, we tried to moved SR3 in Yaw direction with oscllating SRM in Yaw direction. When SR3 moved to -100 urad from initial good setpoint, we can see the beam spot refleted from SRM in POP-SPOL camera. Moreover, the flash signals were observed in the additional PD and REFL PD when the beam spot reflected from SRM was overlaped on the beam spot reflected from ITM. Then, we stopped the excitation and set the actuator output when flash signal is observed in PDs (fig.1). 

However, the beam went away from AS PDs and camera when SRC flashes.

Abstract

Details

A permission error occurred during the callback process from the HWP control PC to k1script.

k1script0
The callback from HWP, which had been specified in .ssh/authorized_keys, was commented out.
Since this was an emergency response, we first restored the original settings. Because the callback for the final move command was malfunctioning, we first performed a command-line callback from the HWP control PC to k1script0 to restore the callback that had been causing the permission error.
After that, we confirmed that HWP was responding correctly to commands from Guardian and performing the necessary processing.

I implemented the hierarchical control for TM with the Oplev. To feed back the DC signals to the IM pitch and yaw, the transfer functions from the IM actuator to the TM Oplev were measured (Ptot 1 and 2). The "DC" (FM9) in the OLDAMP FILTERS in the TM loop was switched off, and the "int" (FM10) in the OLDAMP FILTERS in the IM loop was switched on. The cross-frequency between the TM and IM loops is now below 0.1Hz (I couldn't edit the filter modules in Foton due to the file errors).

These are the results of verification conducted using the test bench at the SK Computer room.

K-Log#36698
>  Remaining concern
> Only remaining concern is that it takes a few hours for synchronizing IRIG-B when a cold boot of the front-end computer is performed. In the past, similar things often occurred when down time became so long and a room temperature changed largely maybe because it took long time to be stable in the temperature of a crystal oscillator of timing slave. On the other hand, in this time, it takes long time even when a down time is only a few seconds. Such a thing wasn't reproduced in the test bench. So we have no idea to solve this issue now.

The abnormal behavior of IRIGB_TIME could also be reproduced in the SK computer room.
We believe the cause lies in the IRIG-B card itself.
Using a test bench that operates normally, when the IRIG-B card (S/N: 3799) was installed, both decreases and increases in the value were observed.
Afterward, the issue still occurred even when replacing the system with the old IO chassis (V1 IO Chassis).
No issues have been observed with the following IRIG-B cards at SK computer room:
02181
3796
02174
3793
02158
02172
=> Tested in slot 2 with full-height configuration; all others are Low-profile
02171
=> Both the yellow and green LEDs light up, and the yellow LED does not turn off (possible connection failure on this card?)

Based on the above observations, we believe this issue is specific to individual IRIG-B cards.

Additional note: We need to consider that this issue is not caused by the IRIG-B card alone, but is occurring in combination with other factors.

• python3-foton package was installed for loading kagralib.py. Because the automatic filter generation function by Guardian that Nakano-kun used is likely no longer in use, python3-foton may no longer be necessary.
• Log-in configuration from the new guardian server to k1dc0 and TCam servers was set for SYS_DAQ and TCam guardians. Now DAQ kill and Taking TCam photos work fine on the new guardian server.
• Thanks to the net-masquerade for PICO network by k1script, HWP in LSC_LOCK guardian can be used without any modification.
• Mode analysis binary can be used also on the new server without any linker mismatch.
• Taking GigE picture for mode analysis of OMC_TRANS haven't work yet due to missed some plugins of GStreamer. Set up of them on the new guardian server will be required.

I checked the TM transfer functions in a vacuum. The IP setpoints were reset to the original (-164 to -550 for L and -24 to -50 for T), so the Length Oplev was also aligned. The transfer functions were consistent with the references.

I checked the IM transfer functions in a vacuum. They were the same as the recent situation in the vacuum (the DC gain is smaller than the reference, except for L and H1).