I offloaded the BF GAS with the FR.

I offloaded the F0 GAS with the FR.

I offloaded the F0, F1, F2, and F3 GAS filters with the FRs.

Since we decided to restore ITMY height, I reverted ITMY GAS related SDFs (fig1).

I offloaded the BF GAS with the FR.

Since ITMY MISALIGNED state doesn't work well due to the MN actuator efficiency reduction (klog33426), I modified the TypeA params.
Now, offsets of 600 cnts at MN_OPTICALIGN_P_OFFSET is added at MISALIGNED state not to saturate the MN actuators.

Also, I managed MISALIGNED_BF state: this state misalign the suspension by -3 mrad in yaw by changing the BFY setpoint.
Since misaligning TM with 600 cnts MN offset is not enough to avoid reflection beam back to REFL table, it is better to use MISALIGNED_BF state for single arm lock.

I checked the DARM spectrum before and after this work (fig1).
I used the best DARM error signal data I could find between 2025/04/14 17:10 UTC and 2025/04/14 21:40 UTC for the reference (blue).
I also used the best DARM error signal data I could find between 2025/04/15 08:10 UTC and 2025/04/15 08:50 UTC for the current data (red).
Black line shows the frequency of the ITMY resonances (lower: vertical, higher: pitch).
The noise around 44 Hz seems to be reduced, so it is worth to install the resistances for all the TypeA suspensions.

I thought 6% P2L coupling corresponding to 6mm miscentering but Komori-kun pointed out it is 6cm miscentering.
So, it would be too large but let's check the sensitivity anyway to check the efffect of resistance installation.

Abstract:

I estimated P2L coupling due to MN HPCD noise (1e-8 V/rtHz at coil driver output).
If we assumed 6% of P2L coupling, slope around 44Hz (ITMY pitch resonance) can be explained.

Detail:

To estimate the MN HPCD noise, I used TF from MNP to TMP, which was measured for peak identification.
Figure 1 shows the measured TF from MNP excitation to TMP.
Since excitation was had a band-pass filter from 10Hz to 60Hz, TF seems to be well measured only from 3Hz to 45Hz but it is enough for checking the coupling around 44Hz.

High power coil driver noise is measured as 1e-8 V/rtHz, which corresponding to the noise of 3.23e-5 cnt/rtHz at COILOFTF input (1e-8/310e-5).
Since EULER2ACT matrix elements from pitch to V1 and V3 coils are -2.9585 and 2.9585, respectively.
So, HPCD noise corresponds to 1.1e-5 cnt/rtHz at SUMOUT_P_OUT.
Since the HPCD noise are incoherent between V1 and V3 while pitch excitation is coherent for them, HPCD noise equivalent MNP excitation is 7.7e-6 cnt/rtHz.
Figure 2 shows the estimated pitch motion of TM stage due to MN HPCD noise.

By using this estimated TMP motion and asuuming P2L coupling rate, we can project the noise into DARM.
Figure 3 shows the projection by assuming 6% of P2L coupling.
Blue and green lines show the HPCD noise projection before and after inserting resistances reported in klog33426.
As you can see, 6% P2L coupling can explain the DARM noise around ITMY pitch resonances and it should be reduced by the inserted resistance effect.

Anyway, let's see the sensitivity curve when PRFPMI will be locked next time.

Note:

Peak height and Q-value in TF data are slightly different from the current peak in DARM, so the projection cannot explain the peak height on the resonance.
No reasonable explanation of 6% P2L coupling but I think it is not so unrealistic.

Similar work with klog33401.

[Aso, Ushiba]

Abstract:

We installed resistances between TM/MN coil driver and coils.
TM actuator efficiency (AE) was reduced by 6dB and MN AE was reduced by 17dB.

Detail:

We installed resistances at ITMY TM/MN actuators to reduce AE.
Procedure is similar with  klog33401 but we put 17dB gain before measuring the actuator gain to keep the AE as much as possibe not to oscilate the local damping control.
In addition, we turned off 1-stage of dewhitening filter not to saturate the MN stage actuator at ALIGNED state.

Figure 1 shows the photo of coil drivers after instllation.
Since TM coil driver switching circuit was interfered with the MNH coil driver cable with resistance, we moved down it by 1U.
After the installation, we measured the TF from each actuators to TM/MN OpLevs and adjusted the gain at FM9 (gain) of each COILOUTF.
Measured data are stored at /users/VISsvn/TypeApayload/ITMY/Spectra/2025/0415/.

After the installation, I modified New_TypeA_params.py so that 2nd stage of dewhitening filter was turned on between ALIGNED state and LOCK_ACQUISITION state to avoid saturation of MN stge during ALIGNED state.
Then, we tried to lock IFO and succeeded, so ITMY modification doesn't seem to disturb the lock acquisition.
However, ue to the large seismic motion, lock durationis too small to check the improvement at this moment.

This is similar work with klog33267.

Related to this model/hardware update, it is necessary to modify the LSC_LOCK guardian because BIO channel name was changed for HPCD.
So, I modified the LSC_LOCK guardian to activate the HPCD dwhitening filters.

The coil driver switcher board (S2516512) was installed at U42 of the IYV2 rack as same as the ETMX case (klog#33152).
For the observation, we don't need to switch the coil drivers during lock acquisition procedures.
This is just a temporal implementation for that we want to keep IFO lock with HPCD in night time and to try using LPCD in daytime.
After we will confirm that IFO lock can be done with LPCD, switcher board will be removed from IYV2 and it will be moved to EY or IX.

At the end of this work, I confirmed that ITMY_TM can be driven by both HPCD (Fig.1) and LPCD (Fig.2).

-----
BIO wiring is completely same as the ETMX case.

DAC assignment for the LPCD output is different from ETMX because the channel assignment of the beacon system was different between ETMX (DAC#2 CH#12-15) and ITMY (DAC#2 CH#0-3). For the beacon system, anti-imaging filters are used special ones to pass through the 24kHz signal. So we cannot use same channels in order to apply proper anti-imaging filters for LPCD outputs. Such an implementation makes us confusing in future. So an implementation of the beacon system must be unified in all Type-A suspensions after O4.

YamaT-san, Ushiba-san, IKeda

Summary
K-Log#33247:Installation of Coil Driver Switcher
=> Reflecting the contents of the model file changed by EX to IY

Details
The basic correspondence is the same as EX, but the following points are different.
The output destination of DAC_2 of TM_{H1,H2,H3,H4} is changed from EX:in12,13,14,15 to IY:in0,1,2,3.

This is because k1sendbeacon and k1sendbeaconiy use EX:in0,1,2,3 and IY:in12,13,14,15 of DAC_2 respectively, and AI has been modified.

Modified Model
K1IY1
 k1visitmylsc
 k1visitmyt

I found that IP damping control oscilated at 8.79 Hz.
Since there was already notch filter at 8.63 Hz (FM7 of IDAMP filters), I changed their frequency.

After changing the notch frequency, the oscillation was disappeared.

Note:

Osillation started from roughly 100 days ago.
I'm not so sure why the resonant frequency was shifted.

I offloaded the BF GAS with the FR.

I changed the setpoint of the heater from 29°C to 27°C at 10:05 JST.

I offloaded the F2, F3, and BF GAS filters with the FRs.

I offloaded the BF GAS with the FR.

To damp 0.64 Hz L resonance, I increased the gain of MN_DAMP_L gilter.
Gain was added FM3 of MN_DAMP_L (ELP9).

I also add resonant gain at 0.64 Hz at MN_MNOLDAMP_P to further damping of this mode.

I added -3dB atFM5 of MN_OLDAMP_P, -5dB at FM3 of MN_OLDAMP_Y, and -2.8dB at MN_MNOLDAMP_Y for adjusting the OLTF to the reference measured before.
Measured OLTF can be seen from "Execute OLG SLOW" at each filter bank.

Abstract:

Since there is a large oscillation of ITMY at 1 Hz in pitch, I checked the pitch control loops.
There is a unnecessary damping filter at NBDAMP_P2, so I turned it off.
Also, overall gain of MN_MNOLDAMP, MN_OLDAMP filter seems different from the reference, so I tuned them.
After these modification, oscillation seems disappeared.

Detail:

After aligning ITMY from MISAIGNED state, a large oscillation at 1Hz in pitch continues for a long time, recently (fig1).
So, I checked the local damping control of ITMY pitch.

Figure1 shows the OLTF of ITMY pitch loop at LOCK_ACQUISITION state.
Blue lines show the reference and green lines show the OLTF before my control modification.
There are three differences:
1. peaks at 1.6Hz.
2. Gain reduction at high frequency.
3. Gain increase at low frequency.

First, I found that NBDAMP_P2 was turned on at LOCK_ACQUISITION state, which is the NB DAMP filter that the other suspensions doesn't have.
Then, I noticed that the same resonance seems to be damped at NBDAMP_L5 and the P2 loop is unnecessary.
So, I turned off the P2 loop.

Then, I increased MN_MNOLDAMP filter gain by 6.5dB and reduced MN_OLDAMP filter gain by 3dB to adjust the gain at high and low frequency to the reference.
Red lines in fig1 show the OLTF after the above modification.
The gain peaking arond 1 Hz reduced a lot and entire OLTF becomes close to the reference.