Tcam images of ITMX and ITMY seemed to change drastically from yesterday.
Figure 1 and 2 show the Tcam images of ITMX and ITMY today and yesterday, respectively.
It might be due to frosting on mirrors by increasing vapor pressure of water molecules due to warming up of duct shields.
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GVbsy and GVbsx was closed by the interlock at 10:27 on December 28, 2025, because the vacuum pressure at BSY reached 1E-3 Pa.
We also turned on heater of both side of IYC at 19:40, because the temperature of this duct shield was enough higher than 150K.
The heater power is about 8W.
Fig. 1: IY-Arm side
FIg. 2: IY-BS side
We turned on the heater on the BRT side of duct shield of EYC at 19:40, because the temperature of this duct shield was enough higher than 150K.
The heater power is about 8W.
Now, both side of EYC duct shields are heating up.
Since GV at both X and Y arms were closed and arm alignment cannot be checked by GR and IR flshes, I requested the ISOLATED state for all Type-A suspensions.
Note:
I don't touch BS, so the reason why BS is ISOLATED state would be the earthquake.
Kimura
Here shows Q-mass plot measured in 6:20 AM on December 28, 2025.
Partial pressure of H2O is still high.
Fig. 1: BS
Fig. 2: IXC
FIg. 3: EXC
Fig. 4: IYC
Fig. 5: EYC
Since I failed upload the screenshot of the heater control panel for the Arm side of the duct shield yesterday, I upload it here.
We turned on the heaters on both side of the duct shield of IXC at 8:19, because the temperature of this duct shield was enough higher than 150K.
The heater power is about 8W.
Now, both side of IXC duct shields are heating up.
I uploaded the screenshot of the heater control panel.
Fig. 1: IX-Arm side.
Fig. 2: IX-BS side.
We turned on the heater on the Arm side of duct shield of EXC at 8:18, because the temperature of this duct shield was enough higher than 150K.
The heater power is about 8W.
Now, both side of EXC duct shields are heating up.
Since I failed upload the screenshot of the heater control panel for the BRT side of the duct shield yesterday, I upload it here.
Fig. 1: EX-BRT side.
Fig. 2: EX-Arm side.
GVitmy was closed by the interlock at 19:09 on December 27, 2025, because the vacuum pressure at Y_00 reached 1E-3 Pa.
After closing GVitmy, the vacuum pressure in IYA (Top-Left of the attached figure) is still 1E-3 Pa.
GVitmx was closed by the interlock at 14:30 on December 27, 2025, because the vacuum pressure at X_00 reached 1E-3 Pa.
After closing GVitmx, the vacuum pressure in IXA (Top-Right of the attached figure) is decreasing.
We turned on the heater on the BRT side of duct shield of EXC at 8:15, because the temperature of this duct shield was enough higher than 150K.
The heater power is about 8W.
Note that we did not turned on the Arm side at this time.
We turned on the heater on the arm side of duct shield of EYC at 8:15, because the temperature of this duct shield was enough higher than 150K.
The heater power is about 8W.
Note that we did not turned on the BRT side at this time.
GVetmy was closed by the interlock at 5:59 on December 27, 2025, because the vacuum pressure at Y_30 reached 1E-3 Pa.
After closing GVetmy, the vacuum pressure in EYC is decreasing.
Since the temperature of the BRT side of the duct shield is still under 150K, increase of the vacuum pressure in EYC due to water evaporation may happen later again.
Because stopping the cryocoolers for duct shields at all area, the heater powers were adjusted at each station.
- Corner station: change rthe setting temp from 18 to 21 for the precision cooler near SR2.
- X end station: Heater power from 0 to 900W.
- Y end station: No adjustment at present.
Please see also characterization works (klog#35926) and the model update work (klog#35961).
K1:CAL-CS_PROC_PMC_FREQUENCY_DQ is now available as calibrated frequency noise of PMC in the unit of MHz.
Though this signal is provided by using K1:PSL-PMC_MIXER_MON_OUT_DQ as the error signal and K1:PSL-PMC_PZT_HV_MON_OUT_DQ as the feedback signal,
K1:PSL-PMC_FAST_MON_OUT seems to be better as the feedback signal because HV output channel is probably contaminated by ADC (or circuits at pick up path) noise around UGF.
Or another solution is to use universal whitening filter for HV output channel.
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Calibration factors
Optical gain (from frequency disturbance to K1:PSL-PMC_MIXER_MON_OUT_DQ) was estimated in klog#35960 as 8.5e-7 V/Hz (OLTF fit) and (1.6+/-1.1)e-6 V/Hz (PDH signal). These two optical gains by OLTF fit and by PDH signal were set on FM1 and FM2 of K1:CAL-CS_SUM_PMC_ERR, respectively, and now one by OLTF fit is enabled because using one by OLTF fit induces a systematic bias only on the overall gain. (On the other hand, using optical gain by PDH signal induces frequency dependent systematic bias around UGF.)
PZT efficiency (from K1:PSL-PMC_PZT_HV_MON_OUT_DQ) used in the optical gain estimation above was estimated in klog#35875 as 889kHz/V. This value was set on K1:CAL-CS_SUM_PMC_CTRL_PZT.
Polarity of each factor
According to the relation between the input voltage to PZT and asymmetric resonant shape by radiation pressure (Fig.2 of klog#35875), increasing input voltage seems to increase frequency. So a polarity of PZT efficiency (Hz/V) should be positive. And also, klog#35875 shows same polarity between Slow out and HV out. This fact suggests that U10 as the switchable sign stage is positive because Both Slow board (JGW-D1301827) and U11 of Main board (JGW-D1301823) have "-1" gain and these two stages are only components having negative gain at the downstream of the Slow output path. This assumption about U10 stage is consistent with klog#35949.
Optical gain estimated in klog#35960 includes a factor of -3.16 by U3 of Main board. According to the overplot of measured OLTF and model, Total optical gain seems to be positive. This means the optical gain from frequency to the input of U3 stage is negative. It depends on the phase relation at RF mixer between LO signal and PD signal. But it hasn't probably checked independently yet. Anyway, from the view point of calibration, a polarity of sensing path can be regarded as positive based on the consistency of measured OLTF and model in klog#35960klog#35960.
Finally, we can get calibrated signal as follows.
V_err = (delta_f + H_pzt * V_ctrl) * H_c
<=> delta_f = (1/H_c) * V_err - H_pzt * V_ctrl
where both H_c and H_pzt are positive.
Thoughts about calibrated signal
Spectra of calibrated signal (Red), (1/H_c) * V_err (Green), and H_pzt * V_ctrl (Blue) are shown on the upper left panel in Fig.1. Blue curve corresponds to the past calibration which was provided by using only feedback signal and we can see a difference from better calibration especially above UGF. According to the transfer function between (1/H_c) * V_err (Green) and H_pzt * V_ctrl shown in the right panels in Fig.1 (this TF corresponds to the OLTF model on the front-end calibration), UGF is around 1.3kHz.
One important notice is coherence between these two signals are not so high above 10Hz (see also the lower left panel in Fig.1). I tried to tweak calibration filters but I cannot improve the situation by using digital whitening technique. This fact suggest bad coherence between error and feedback signal comes from ADC or circuit noise at DAQ pick up path instead of numerical rounding issue by digital signal processing. So I also checked coherence between raw error signal (K1:PSL-PMC_MIXER_MON_OUT_DQ), TTFSS output (K1:PSL-PMC_FAST_MON_OUT_DQ), and HV output (K1:PSL-PMC_PZT_HV_MON_OUT_DQ) as shown in the upper panel of Fig.2. Then, HV output has poorer coherence with the error signal than TTFSS output probably due to a low gain by the pomona box at the input port of HV amp (see the lower panel of Fig.2). And also, calibrate spectra of HV output is louder than one of TTFSS output around kHz band. It seems to be a contamination by ADC noise.
From these results, we can conclude that TTFSS output is better as feedback signal for calibration than HV amp output. On the other hand, using HV amp output makes calibration simple. So it's probably good to use universal whitening filter for PMC control signals to mitigate poor SNR at ADC.
Nakagaki, Yasui
We stopped two duct shield cryocoolers.
12:36 Xer (The compressor operating time was 12226.5h)
12:37 Xea (The compressor operating time was 10352.1h)
Nakagaki, Yasui
We stopped two duct shield cryocoolers.
10:55 Yea (The compressor operating time was 12438.6h)
10:56 Yer (The compressor operating time was 20314.0h)
Nakagaki, Yasui
We stopped two duct shield cryocoolers.
9:57 Yfs (The compressor operating time was 24008.4h)
9:57 Yfa (The compressor operating time was 26226.1h)
Nakagaki, Yasui
We stopped two duct shield cryocoolers.
9:55 Xfa (The compressor operating time was 22791.1h)
9:56 Xfs (The compressor operating time was 18290.6h)
ARM : Y
TEMP ITM : 203.1
TEMP ETM : 199.9
NUM : 5
IFO REFL HWP : 125.0
PSL HWP : 173.0
IMC POWER : 12.4
VALUE : 1278.4
ERROR : 6.0
Measured data is stored to /users/Commissioning/data/Finesse/Yarm/20251226-041845
We exchanged k1tw0 SSD for the new one.
The data recorded on the previous SSD is currently being copied to the NFS server.
The data from the last six months is being temporarily loaded from an external disk. We plan to switch to a NAS storage space next week.
With recent data growth, a 2TB disk will fill up in approximately 5.5 months.
Oshino-san, Ikeda
Entered IXV and IYV rooms around 11:30 AM
IXV: Pre-check for K1IX1 IO chassis replacement
IYV: k1ctr14 was hung, so restarted by holding the power button
A calibrated signal will be available after checking sign of each component.
BTW, some SDF differences appeared as shown in Fig.1-2 when I restarted k1psl.
They seemed to be related numerical rounding issue. So I reverted them.
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Yamamoto-kun told me that some of the catalogs in the Japanese version said the wrong value as 15urad/V, but the correct value seems to be 15mrad/V
- https://www.newport-japan.jp/pdf/848.pdf
- https://www.newport.com.cn/p/4004
- https://www.manualslib.com/manual/3403554/New-Focus-400-Series.html?page=8#manual
We divided the result by 2 *pi, but it was wrong. Conversion between Phase [deg] to Frequency [Hz] is: Frequency = d(Phase)/dt (or 1/(2*pi)* d(phi)/dt for angular frequency). So the pure actuator efficiency of the wideband EOM will be 6.24mrad/V. If you see from the FAST output of IMC servo, the efficiency is 1.25rad/V, including 200 times gain of RF amplifiers.