Saito-kun,
Could you upload the overplot graphs of the raw data and the fitting functions similar to fig 2 and 3 in klog37201?
[Aritomi, Ushiba, Tanaka, Saito]
Sub-laser light was injected into the SRY, PRY, PRX, and SRX, and a PLL was established. The LO frequency was then swept to scan the beat signal. Using the maximum hold function of the Moku:Lab spectrum analyzer, transmission power as a function of frequency was recorded around 190 MHz, 160 MHz, 140 MHz, −140 MHz, −160 MHz, and −190 MHz. The data were fitted both with and without a linear background, and the maximum and minimum peak frequencies within the corresponding fitting uncertainties were determined. The cavity lengths were then calculated from these results. The differences between the measured cavity lengths and the design values were 0.15 ± 0.33 cm for PRY and 1.58 ± 0.82 cm for SRY. Therefore, the PRY measurement is consistent with the design value within its uncertainty of 0.33 cm, whereas the SRY measurement differs from the design value by more than the estimated uncertainty, suggesting that the actual cavity length may differ from the design value. The results for PRX and SRX will be reported after the analysis is completed.
For the data near each resonance peak, fitting was performed both with and without a linear background, following the same procedure as in the previous analysis (klog:37201). From the fitted peak frequencies and their uncertainties, the maximum and minimum frequencies within the fitting uncertainty were determined. The overall uncertainty range was then defined as the largest and smallest values obtained from both fitting models. The following data were used to determine the PRY and SRY cavity lengths.
PRY
Minimum (MHz) Maximum (MHz)
186.9049 186.9561
163.8426 163.8974
131.4761 131.5159
-115.5105 -115.4909
-157.0807 -157.0589
-189.4049 -189.3442
SRY
Minimum (MHz) Maximum (MHz)
186.8354 186.9305
166.0559 166.2530
131.4035 131.4918
-127.2003 -126.2609
-159.4324 -159.3557
-189.3570 -189.2707
From the measurement results, the midpoint between the minimum and maximum frequencies was calculated for each resonance. These midpoint frequencies were divided by the FSR calculated from the design cavity lengths (64.9265 m for PRY and 64.9264 m for SRY). The resulting values were rounded to the nearest integers, and the measured frequencies were fitted with the linear function AN+B, where A and B are fitting parameters and N is the rounded integer. The fitting results were as follows.
PRY (Fig. 1)
A: 2.30865 ± 0.00012 MHz
B: −0.0741 ± 0.0074 MHz
SRY (Fig. 2)
A: 2.30815 ± 0.00029 MHz
B: −0.092 ± 0.021 MHz
Since A corresponds to the FSR, the cavity lengths were calculated from the fitted values of A.
PRY
Measured cavity length: 64.9280 ± 0.0033 m
Design value: 64.9265 m
Difference (measured − design): 0.15 ± 0.33 cm
SRY
Measured cavity length: 64.9422 ± 0.0082 m
Design value: 64.9264 m
Difference (measured − design): 1.58 ± 0.82 cm
Therefore, the PRY measurement is consistent with the design value within the uncertainty of 0.33 cm. In contrast, the difference between the measured and design values for SRY exceeds the estimated uncertainty, suggesting that the actual SRY cavity length may differ from the design value. The results for PRX and SRX will be posted once the analysis has been completed.
With Misato Onishi, Yuli Liang, Jinshui Tian
We installed 2 QPDs in Rx module on 7/14 for the Pcal beam monitoring.
And, I took Tcam data with changing Pcal beam positions by the pico PCAL_EY2 in the 7/15 morning.
The data will be analysed to check the QPD performance.
With Dan Chen, Yuli Liang, Jinshui Tian
We continued the work from the previous day. (37183)
Before starting the work, we recorded the alignment of the current YPcal laser using the previously prepared reference setup.
We reduced the power of the main beam path of new laser using HWP before performing the alignment work.
We aligned the beam from the new laser and successfully extracted it from the Tx module.
At the end of the work, we turned on the current laser and checked the beam position on the RxPD.
No significant change was observed, indicating that the installation and alignment work had not affected the alignment of the existing laser.
I collected the high-power coil driver (HPCD) from EYV (S1604763) and brought it back to Mozumi.
According to Saito-kun, HV amp (x10) was directly connected to the laser PZT input for the PLL lock. According to my past experiences, the direct connection tends to excite PZT at high frequency.
To solve this problem, we inserted a passive LPF that is set as one of the filters for the control servo between the PZT input and the HV. According to my memory, 10Hz ?? LPF and 100kHz?? LPF were used as one of the control filters. So what I can suggest is to set a passive LPF btw the PZT and the HV, and remove the same LPF in the control filters. I have a ponoma case and a film condenser (400V?) in my room.
Another concern is that the UGF at 10kHz for the PLL control might to excite some resonances of the PZT as in the main laser frequency stabilization servo.
I performed the initial alignment Xarm, Yarm, OMC, PRMI and SRY.
[Aritomi, Ushiba, Tanaka, Saito]
The sub-laser was injected into SRY, and the PLL was engaged while the LO frequency was swept to scan the beat signal. Using the maximum hold function of the Moku:Lab spectrum analyzer, the SRY transmitted power was recorded as a function of frequency. Because the slopes on the two sides of the resonance peak were different, the data were fitted both with and without a linear background offset. The two fitting methods yielded resonance frequencies differing by approximately 47.9 kHz. If this difference is regarded as the fitting uncertainty, it is comparable to the measurement uncertainty reported previously (klog:37191). The PLL UGF was then reduced to narrow the beat-signal linewidth, and the measurement and fitting procedure was repeated. However, the fitted resonance frequencies with and without a linear background offset differed by approximately 143 kHz, indicating that the fitting uncertainty was not improved. To achieve more accurate fitting, it will likely be necessary to suppress fluctuations in the beat-signal amplitude and reduce the influence of higher-order modes.
[Jinshui Tian, Yuli Liang, Dan Chen]
On 2026/07/09, we updated the Pcal Reconstruction model for both EX and EY so the output Pcal beam position is consistent with the calculation in the paper: Performance of the KAGRA photon calibrators during the fourth joint observing run with LIGO and Virgo - IOPscience.
We deployed the updated model files into the production environment via k1ctr27 (replacing the original files) and confirmed the GRD and SDF statuses.
We then recompiled, installed, and restarted the front-end models as follows:
EX Model (k1ex0):
ssh k1ex0
cdscode
make k1calex
make install-k1calex
startk1calex
EY Model (k1ey0):
ssh k1ey0
cdscode
make k1caley
make install-k1caley
startk1caley
From ndscope, observable value steps were noted on the following channels:
EX Channels: K1:CAL-PCAL_EX_A_X_MON & K1:CAL-PCAL_EX_A_Y_MON at GPS: 1467955200 s
EY Channels: K1:CAL-PCAL_EY_A_X_MON & K1:CAL-PCAL_EY_A_Y_MON at GPS: 1467956800 s
We plan to calculate and compare the pre- and post-update channel data tomorrow.
[ Yasui, Oshino, Nakagaki ]
We have installed a system to monitor the open/closed status of the manual gate valve between PRM and PR3.
The open/closed status is provided via the following PVs:
K1:VAC-GV_PR3_OPEN
K1:VAC-GV_PR3_CLOSE
These have also been added to the `VAC_OVERVIEW` MEDM screen.
Since we were unable to test the valve in the closed position today, we will conduct that test at a later date.
Because the LPD values went down in these days, Pcal GRD went to FAULT state today.
I think this is caused by the instability in the laser source.
So I changed the threshold value from 3.3 to 3.0.
I compared the spectra in the IRM damper servo ON/OFF again. The IP was excited in yaw with the IP actuators. The servo gain was increased from 1.5 to 2. Although the peak around 60 mHz was damped by the servo, the RMS reduction was small due to the resonance at 160mHz.
I collected the high-power coil drivers (HPCDs) from IXV (S1604827) and IYV (S1706250) and brought them back to Mozumi.
I collected the high-power coil driver (HPCD) from EYV (S1604763) and brought it back to Mozumi.
[Tanaka, Hirose, Fujimoto, Saito]
Following the same procedure as in the previous measurement (klog:37185), the lengths of PRY, SRY, and SRX were measured. The differences between the measured and design values were 0.6 ± 1.2 cm for PRY, 1.5 ± 1.3 cm for SRY, and 2.8 ± 1.6 cm for SRX. Therefore, the PRY measurement is consistent with the design value within the measurement uncertainty of 1.2 cm, whereas the differences for SRY and SRX exceed their respective uncertainties, suggesting that their actual lengths may differ from the design values.
As in the previous measurement (klog:37185), the sub-laser was injected into PRY, SRY, and SRX, the PLL was engaged, and the beat signal was observed with the RFPD installed at OMC REFL. The minimum and maximum frequencies at which the beat-signal amplitude reached its maximum were measured. The results are summarized below.
PRY
Minimum Maximum
161.501 MHz 161.583 MHz
138.351 MHz 138.485 MHz (assuming ±67 kHz around 138.418 MHz)
−140.999 MHz −140.865 MHz (assuming ±67 kHz around −140.932 MHz)
−161.783 MHz −161.649 MHz (assuming ±67 kHz around −161.716 MHz)
SRY
Minimum Maximum
161.371 MHz 161.492 MHz
140.6095 MHz 140.7305 MHz (assuming ±60.5 kHz around 140.67 MHz)
−141.0055 MHz −140.8845 MHz (assuming ±60.5 kHz around −140.945 MHz)
−161.7595 MHz −161.6385 MHz (assuming ±60.5 kHz around −161.699 MHz)
SRX
Minimum Maximum
−160.384 MHz −160.244 MHz (assuming ±70 kHz around −160.314 MHz)
−140.65 MHz −140.51 MHz (assuming ±70 kHz around −140.58 MHz)
162.316 MHz 162.456 MHz (assuming ±70 kHz around 162.386 MHz)
140.33 MHz 140.47 MHz (assuming ±70 kHz around 140.400 MHz)
During the measurements, the sub-laser temperature was changed significantly when switching the beat frequency from +160 MHz to −160 MHz. Under these conditions, the beat frequency observed at OMC REFL fluctuated much more frequently, suggesting that the fluctuations become significant until the sub-laser temperature stabilizes. In addition, after switching from +140 MHz to −140 MHz during the SRY measurement, the frequency fluctuations did not subside. However, when the MCE feedback was enabled during the subsequent SRX measurement, the fluctuations were noticeably reduced. This suggests that fluctuations of the main laser also contribute to the beat-frequency instability.
For each cavity, the midpoint between the measured minimum and maximum frequencies was calculated and divided by the corresponding FSR calculated from the design lengths of 64.9265 m (PRY), 64.9264 m (SRY), and 68.2562 m (SRX). The resulting values were rounded to the nearest integers, and the measured frequencies were fitted with the linear function AN+B, where A and B are fitting parameters and N is the corresponding integer. The fitting results are as follows.
PRY (Fig. 1)
A = 2.30892 ± 0.00044 MHz
B = −0.091 ± 0.030 MHz
SRY (Fig. 2)
A = 2.30818 ± 0.00046 MHz
B = −0.136 ± 0.030 MHz
SRX (Fig. 3)
A = 2.19520 ± 0.00051 MHz
B = −0.076 ± 0.035 MHz
Since A corresponds to the FSR, the cavity lengths obtained from the fitted FSR values are
PRY
Fitted length: 64.921 ± 0.012 m
Design length: 64.9265 m
Difference (Fitted − Design): −0.6 ± 1.2 cm
SRY
Fitted length: 64.941 ± 0.013 m
Design length: 64.9264 m
Difference (Fitted − Design): 1.5 ± 1.3 cm
SRX
Fitted length: 68.284 ± 0.016 m
Design length: 68.2562 m
Difference (Fitted − Design): 2.8 ± 1.6 cm
Therefore, the measured PRY length is consistent with the design value within the measurement uncertainty of 1.2 cm. In contrast, the differences between the measured and design values for SRY and SRX exceed their respective uncertainties, suggesting that their actual cavity lengths may differ from the design values.
ETMX went to PAY_TRIPPED at 13:56 JST due to glitches on MN V1 photosensor (Fig.1).
ETMX was in MISALIGNED (STATE_N=1400) and all payload control was disengaged, so it's not caused by the local control.
Similar glitches appeared several times before going to PAY_TRIPPED (Fig.2).
This situation is similar to klog#29475 (ITMX_MN_V1), klog#31522 (ETMY_MN_V1), and klog#32077 (ETMY_MN_V2).
If glitches will appear again, it might be better to stop using ETMX_MN_V1.
Pictures: link