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).

I checked the GAS transfer functions in a vacuum. They were consistent with the references.

I checked the IP transfer functions in a vacuum. IDAMP signals are not treated well, so please see the LVDT responses in BLEND signals. The resonant frequencies of the IP were 63mHz for L, 74mHz for T, and 0.32Hz for Y, respectively.

EYC1F temperature seemed to have decreased by 2 C degrees for 2 months.

I increased the heater power as follows,

• Delonghi 0 -> 1.2kW
• Sunrise 1 : 900W -> 1.2kW
• Sunrise 2: 600W -> 1.2kW

[Tanaka, Hirose, Saito]

We confirmed that the Moku:Lab was operating properly. We also set up the system so that the local oscillator frequency could be continuously adjusted while monitoring the beat signal frequency. Although various types of filters were tested, the control system unfortunately did not function.
 

• Following the previous attempt (klog:36845), we continued working on the PLL. First, to verify that the Moku:Lab was functioning correctly, we connected its output to its input and confirmed that a constant voltage applied at the output was observed unchanged at the input. Next, we confirmed that the error signal was properly output when passed through a flat (0 dB) filter.
  We then split the beat signal into two using a power splitter and used an additional Moku:Lab as a spectrum analyzer to continuously monitor the beat signal, allowing us to match the local oscillator frequency accordingly. Observing the mixed beat signal and local oscillator signal on the Moku:Lab oscilloscope, we saw that the amplitude of the error signal fluctuated and its frequency also varied (Photo 1). The red line represents the error signal, and the blue line represents the feedback signal. In this state, we applied various filters, including flat, high-pass, and low-pass filters, but no significant change in the error signal amplitude was observed. We also attempted to measure the open-loop transfer function; however, it did not appear that any meaningful measurement was obtained. Therefore, it is likely that feedback was not properly established. In addition, since the feedback signal amplitude was limited to a maximum of ±1 V, it may have been too small to achieve lock. It may be necessary to amplify the signal using an SR560 or a similar device before feeding it back to the laser PZT.

[mTakahashi, Yasui]

We tried a nitrogen purge to promote H2O removal.
9:37 9.3e-1 Pa
9:44 stopped the dry pump
9:58~ N2 purge
10:09 8.8e3 Pa
10:12 started the dry pump
13:14 24 Pa(SRM), 9.2e-2 Pa(OMMT)
13:15 GVommt open->14Pa(SRM), 12Pa(OMMT)
13:16 started the TMP
So far, the pressure has decreased faster than in the previous trial on April 24.
It took 1 hour 8 minutes to reach 4e-4 Pa from 1e-2 Pa this time, whereas it took 10.5 hours last time.  The nitrogen purge seems to have been effective.

[Tanaka, Saito, Hirose]

Yesterday, as preparation for klog36845, we performed the initial alignment of Xarm and Yarm. Then, we noticed that the feedback signal for the OPLEV control of the PITYAW on SR3 had changed significantly compared to the previous Yarm flash. We confirmed that it has been specifically moved to 4/23 PM1:50JST(fig1). When we performed Lissajous the PITYAW on SR3 so that Yarm would flash again, the optimal YAW value had changed from -9 urad to 55 urad(55urad: fig2).

[Tanaka, Hirose, Saito]

We constructed the PLL control system in which a feedback signal was generated using a mixer, a local oscillator, a SR560, and a Moku:Lab, and fed back to the PZT of the sub-laser. Unfortunately, the control system did not function successfully.
 

• Since the previous observation of the beat signal (klog:36835), the sub-laser had remained on with its temperature kept at 31.57 ℃. Under this condition, a beat signal was observed; however, its amplitude changed significantly, and its frequency drifted by about 5 MHz over approximately one minute. Because the frequency was close to 0 Hz and the range over which it could be further reduced was limited, we increased the sub-laser temperature to 31.60 ℃ to raise the beat signal frequency to about 112.1 MHz (Photo 1). Next, this beat signal and a local oscillator signal (112.1 MHz, 10 dBm) were input to the mixer to generate an error signal. The mixer output was then fed into the SR560, where it was amplified and passed through a first-order low-pass filter with a cutoff frequency of 1 MHz. The output of the SR560 was subsequently input to the Moku:Lab, where an integrator was applied using a PID controller (Photo 2). The output of the Moku:Lab was connected to the PZT of the sub-laser, and the overall gain was varied. However, the error signal did not decrease, and no change was observed in the feedback signal. The error signal amplitude was 1.090 V; however, when the local oscillator frequency was set to 90 MHz, it became 409.5 mV, and at 80 MHz, it became −154.0 mV, indicating that it varied with the local oscillator frequency (Photo 3). On the other hand, changing the temperature of the sub-laser did not result in any noticeable change in the error signal amplitude. This suggests that the signal being treated as the error signal may in fact be a different signal. It is also possible that the Moku:Lab was operated incorrectly.

[R.Takahashi, Washimi, Kimura, Yasui, M.Takahashi, Sawada]

We reinstalled the geophone pods. Additionally, we adjusted the tilt of the FLDACCs. The feedback signals to the proof mass(COILOUTF) became smaller: +12200 to +1400 for H1, +12500 to -500, and -4900 to +2200 in count, respectively.