Takano, Ushiba, Hirose
After the RFAM HWP work was down, we tried PRXARM. We could lock PRXARM_3F. IMC power was 0.56.
And we implemented PRXARM's ADS in ASC_LOCK Guardian. I will post the details later. At the end of the work, I set PRM to "LOCK_ACQUISION" and ITMX and ETMX to "MISALIGNED".
Uchiyama-kun tried to set the water pump operation only by the No.2 pump, but the alert (E01: inverter trip) kept and he could not stop this alert by pressing the reset button.
So, he tried to set the water pump operation only by the No.1 pump, then it worked without alerts. So we guess, the there seemed to be wrong in the controlers or sensors. At least it kept working over 12 hours.
Hirose, Takano, Ushiba
We noticed that when we request "PREP_FOR_XARM_ALIGN" SR2 and SR3 are requested to "ALIGN" although they are not necessary for X arm alignment. This request caused the trip of SR suspensions. Of course I know that for OMC alignment with X arm locking these two should be aligned, but not necessay to align them at the preparation for X arm.
Therefore, I modified the guardian so that SR2 and SR3 are requested to align when "PREP_ALIGNMENT_TO_OMC" is engaged. If they are already aligned, the guradian will do nothing.
Takano, Tanaka, Ushiba
Related to this work, the output power of PSL is now below the threshold (1.35 W) for tuning of HWP in LOCK_PREP state of IMC guardian. I modified the guardian to skip this check and go to the next state. After incresing the laser power this modification should be reverted.
When we requested LOCK_ACQUISITION state to SR2, SR2 was tripped at TWR_DAMPED stte.
After several investigations, we found that the trip was because F2 GAS position is too far from the nominal position.
I passed TWR_DAMPED state by adding offset to F2 GAS manually, so now SR2 is in LOCK_ACQUISITION state but it is necessary to offload GAS filters.
Since ITMX_NBDAMP_Y1 loop starts to oscilate when we requested LOCK_ACQUISITION state, I changed the gain from 1 to -1.
I also modify the guardian parameter in the New_paramA.py (fig1) to keep this configuration.
Basically, VIS control loop sign is managed so that working with a filter gain of -1.
So, it is better to unify the sign of the gain of each loop in the end.
I plotted the spectrograms for the 40-500Hz swept sine ground shaker injection test with single-bounce (klog30511)
We couldn't see any excess in the OMC trans signal except for <100Hz injection.
Response from the displacement () of the cavity to the relative intensity (
):
Fluctuation in a certain frequency:
Amplitude of response at the second harmonics of the original frequency:
I projected the Geophone signal into the OMC error signal using the TFs in klog30521, measured by shaker injection tests.
For the frequencies the TF value was not measured due to bad coherence, I set 1e-3 counts/(um/s) as an upper limit.
I calibrated the transfer function from a geophone on the optical table of OMC chamber to OMC length error signal as shwon in Figure1. Now the unit is in [m/m].
Peak values
82 Hz: 0.0132 (7/19), 0.0117 (7/22)
92 Hz: 0.0054 (7/19), 0.0040 (7/22)
I also projected the coupling noise from geophone to OMC length with data of quiet time just before the injection tests on 7/19 and 7/22. It seems that the contribution of these resonant peaks are close to the current sensor noise level of OMC length.
I crosschecked the OMC length noise from the measurement done on July 22.
Figure 1 shows the diaggui file, which I used for the calculation.
According to the OMC SUM during the measurement (fig2), OMC transmission power was about 29 mW, so I calibrated K1:OMC-TRANS_DC_SUM_OUT_DQ to RIN by dvided with 29.
According to klog30535 and klog50539, the calibration factors estimated from two different method were 5.1e9 and 6.4e9 cnt/m, respectively.
So, I used the averaged value, 5.75e9 cnt/m, for the calibration of error signals to displacement.
I also calibrated geophone signals and seismometner signals to displacement by devided with 2*pi*f (I could not confirm current calibration is um/s for both geophone and seismometer at OMC, so it might be wrong. If so, please let me know).
Around 92 Hz (injection frequency), RMS of OMC error signals were 2.2e-12 m.
According to the PZT actuator efficiency, 1.3e-10 m/cnt (klog30490), and cavity scan of OMC (fig3), FWHM in the unit of meter is 1.3e-10*5.5 = 7.2e-10 m.
So, RIN of OMC transmission generated by the displacement around 92 Hz can be estimated as 2*(2.2e-12/7.2e-10)**2~2e-5.
According to the direct measurment of RIN of OMC transmission, RMS of RIN around 184 Hz, which is double of the injection frequency, is about 1.9e-5 (fig5), which is almost consistent with the value estimated above.
So, the above estimation method from OMC error signals to RIN of OMC transmission seems to work well.
The transfer function from geophone to OMC error signals at 92 Hz is 0.0023, according to the measurement (fig6).
Now, let's say OMC vibration around 92 Hz without excitations is 1e-11 m/rtHz according to the measurement (fig7).
OMC length displacement can be estimated as 1e-11*0.0023=2.3e-14 m/rtHz
So, RIN of OMC transmission will be 2*(2.3e-14/7.2e-10)**2~2e-9, which is lower than shot noise limit of 15mW OMC transmission, 5e-9.
According to the TF measurement from geophone to OMC error signals (klog30521), the gain from geophone to OMC error signals at 92 Hz is larger than that at the other frequency, except for 82 Hz: this means RIN of OMC transmission would be lower than 2e-9 at the other frequencies.
So, it might be difficult to explain the OMC noise floor above 100 Hz only by optical table vibration on the OMC stack.
(This is an analysis of the 7/19 and 7/22 data)
I also checked the TFs from the ground seismometers (X/Y/Z) to the vac-table geophone (Y).
For most frequencies, the amplitude was larger in the ground-shaking than in the duct-shaking case.
It suggests that the vibration from the duct propagates to the optical table through the stacks, rather than short-cutting through something (e.g. cables).
Miyakawa, Takano, Tanaka
This is a brief repor of the RFAM reduction trial done yesterday. The detail will be posted later.
We noticed that the our work done on Tuesday was totally wrong. Therefore, we first reduced the output power at PMC down to 1 W and set the polarization to s-pol, which we think is optimal for EOM to generate PM sideband. Next we directly measured RFAM with another RFPD after EOM1 without any polarizer before this PD, and observe that there are peaks at 13.7 MHz (f_imc) and 15 MHz (f_pmc). Around 45 MHz (f2) the peak seemd to be buried under the noise floor. When rotated the HWP so that the peak at f_imc is minimized, the peak height at f2 got higher. This implies that the best condition for f_imc and f2 is different.
After that, we recover the main beam path and tuned the wave plates so that RFAM measured by the RFAM was minimized and went out PSL room without increasing the output power. From the outside of PSL room, we rotated the HWP before two TFPs by ~ 280 deg, and checked the maximum and the minimum power. We confirmed that the minimum power was closed to zero, which means that the output power after EOM2 was close to pure linear polarization.
Finally we locked IMC and aligned PRM in order to check the offset of the demodulated signals from RFPDs on REFL table. We observed that the amplitude of these offset values were about one order smaller than the previous value.However, now the DC power at these PDs were almost half of the previous measurement because of lower power at PMC trans, so the actual reduction ratio is about ~ 5. Anyway, we are concident that the current RFAM level is improved by tuning the polariaztion in front of EOMs.
[Sato, YokozaWashimi]
Yesterday we performed the same measurements at the REFL, BS, and IXC areas and evaluated the TFs of sound. The results are plotted.
At the begging of the work, Yokozawa-san found the 20dB amplifier for the IXC microphone was not engaged and turned on it. We confirmed it can detect sound.
Because I set the target temp of the precision cooler for the PSL room to 22.00 (Nominal is 23:00) to cool inside effectively, the present temp in the PSL room might be cooler than before. So it might affect the PLL lock and so on. I will recovery the temp if I can obtain data on PT01~05 again.
[Kimura and M. Takahashi]
On 25 July evening, we turned on six Ion pumps of IXC and IYC and turned off six TMPs and dry pumps of IXC and IYC.
Around 8:20, Uchiyama-kun reset the alert with a "ブザー停止" button in the control panel.
After the restart around 8:30AM on 25th July, again on 20:17 on the same day.
We expected something would happen around 14:30 that was 6 hours after the restart, but nothing happened. However, alert again after 12 hours from the restart. So we expect something such as switching of the water pump every 12 hours.
