> Tomorrow, we plan to install and connect patch panels to the racks, as well as test the cables.

We have completed the installation and connection of the patch panels in the rack, as well as cable testing.
Connections:
From 2F EY1 (Fig. 1) to 1F EY0: 12-fiber MTP cable with 3 wires (Fig. 2); to EYA: 2 wires (Fig. 3)

Since the delivery was delayed, only the two wires for EYA have female plugs on both ends.
Ultimately, all connections will have male plugs (with guide pins) on both ends.

I changed the setpoint of the F0 GAS from 4300 to 4250.

This log summarizes the Guardian modifications made during the commissioning work reported in klog 37825.

1. DRMI Guardian updates

[DOWN]

• Set the demodulation phase of POP RF45 to 73.870 deg. We plan to move the DRMI-related settings to the DOWN state, but only this setting has been implemented so far.

[PREP_FM_FOR_DRMI]

• Set the demodulation phases for DRMI 1f locking as follows:

  • POP RF17: -139.60 deg

  • POP RF45: 73.870 deg

• During this commissioning, the demodulation phases were adjusted to maximize POP45I for PRCL and minimize POP17Q for SRCL.

[LOCKING_DRMI_1F]

The following settings were updated.

• Input matrix (INMTRX). To reduce the coupling between the longitudinal DOFs, the following elements were set:

  • POPA45I (MICH) → SRCL: -9.5

  • POPA17I (SRCL) → PRCL: -0.4

  • POPA45I (PRCL) → MICH: 5.3

• MICH offset. Changed the MICH filter OFFSET from -25.8 to -35.0. After this change, the AS port camera image became slightly darker.
• Output matrix (OUTMTRX). These values were taken from the PRMI and SRMI settings, respectively.

  • MICH → PRM: -0.0404

  • MICH → SRM: 0.23479

• PRCL gain. Set PRCL1_GAIN to 0.85 based on the OLTF measurement.

2. SRY initial alignment

[LOCKING_SRC_3F]

• Changed LSC_INMTRX['SRCL', 'POPA17I'] from 80 to -80. The original value of 80 was the same as that used for SRX, but SRY could not be locked with this setting. After reversing the sign, SRY was successfully locked. The reason why the opposite sign was required is still unclear.

[Ushiba, Hirose, Aritomi, Fujimoto, Kataoka, Sugioka]

Abstract:

We performed adjustments for DRMI 1f.

Details:

 We achieved DRMI 1f locking,and completed the phasing, decoupling, calibration, and UGF adjustments for DRMI 1f.

First, we performed phasing for POP90I/AS34I because they are used for thresholds in DRMI locking state.
Since there seemed low coherencein excitation measurement, we tuned the demodulation phase to minimize the offset in timeseries of POP90Q/AS34Q While PRMI3f/SRMI1f locked(Figure.1).
We also updated LSC_CUST_OUT_MTRX in DRMI to reflect the values from PRMI and SRMI.
Then, we achieved DRMI 1f locking.

After DRMI locked, we performed the phasing for POP17 and decoupled SRCL from PRCL IN1.
We injected 150.125Hz excitation to SRCL. Then we changed the demodulation phase from -149.6 to -139.6 to minimize the peak in POP17Q.
We also set the K1:LSC-PD_DOF_MTRX_4_9  -0.4 to minimize the peak in PRCL IN1(Figure.2).

Next, we performed the phasing for POP45 and decoupled PRCL from MICH IN1 and SRCL IN1.
We nnoticed that exciting IN1 causes the contamination by the different G in each control loop, so here we injected 150.125Hz excitation to K1:VIS-PRM_TM_TEST_L_EXC.
Then, the PD signal is just the product of excitation and A(Actuator efficiency) which is independent from control loop.
We changed the demodulation phase from 57.87 to 78.87 to minimize the peak in POP45Q.
We also set the K1:LSC-PD_DOF_MTRX_3_11 5.3 and K1:LSC-PD_DOF_MTRX_4_11 -9.5 to minimize the peak in MICH IN1 and SRCL IN1(Figure.3).

Then, we adjusted control gain.
We measured OLTF for MICH, PRCL and SRCL(Figure.4,5,6).
The UGF for each control was approximately 50Hz, 30Hz and 100Hz.
Out-to-In measurement was consistent with the suspension model, which verifies that the IN1 signal is calibrated to nm.

All of these parameter changes were updated in Guardian,and the specific Guardian modifications will be detailed in Hirose-san’s upcoming post.

YamaT-san, DanChen-san, Nakgaki-san, Infofarm(4 people), Ikeda

We installed fiber-optic cables from the 2nd floor of the Y End to the mini racks near DGS and EYA on the 1st floor.

Tomorrow, we plan to install and connect patch panels to the racks, as well as test the cables.

With Nakagaki-san

We carried out electrical safety improvements in both the EXA and EYA areas.

Work performed

• Replaced or corrected power cables that had been identified as issues in the fire safety assessment.

• Rearranged the cables and equipment so that the power distribution boxes could be properly closed. (pictures)

• Installed dust-proof safety plug covers wherever possible.

Impact on equipment

• The power cables for the network switches were also included in the replacement work. As a result, network communication with devices connected to the Pcal network switches was temporarily interrupted.

• The affected devices included Tcam and  a vacuum monitor in EYA

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

I changed the setpoint of the F0 GAS from 4200 to 4300.

I measured the IP tilt, which depends on the IP position. The IP position was changed with the setpoint for the LVDT L. The IP tilt was measured using the DC feedback signal in the FLDACC H1 (aligned to L). The plot shows that the DC acceleration in the FLDACC is proportional to the IP position. The coefficient was 2.8μg/mm which corresponds to 2.8μrad/mm in tilt.

This log summarizes the Guardian updates described in klog37816. (SRY locking and the SRC initial alignment have not been tested yet.)

1. Updates to lsclib.py

• The lock threshold for SRMI 3f (is_srmi3f_locked) was added: ezca['LSC-AS_PDA2_RF34_I_NORM_MON'] > 0.05
  This is the same threshold as that used for SRMI 1f. Unlike PRMI, both SRMI 1f and 3f have the 1f sidebands resonating in the interferometer, while the carrier is dark at the AS port due to the Schnupp asymmetry. Therefore, the same 2f1 RFPD signal is used to determine the lock status for both SRMI 1f and 3f.
• The @check_srmi3f decorator was also added.

2. SRX 1f/3f commissioning

[PREP_FM_FOR_SRC]

This state is shared by SRX and SRY, although SRY has not been tested.

• The SRCL1 gain is set to 0.02 for 1f and 0.015 for 3f.

• The HWP angle is set to 146 deg.

[LOCKING_SRC_3F]

In the DOWN state, LSC_INMTRX['SRCL','REFL51I'] is set to 1 by default.

For 1f locking:

• The default SRCL -> REFL51I input matrix element is cleared, and SRCL -> POP17I is set to 80.

• ELP100 is enabled.

• The POP17 demodulation phase is set to 153.00 deg.

For 3f locking:

• SRCL -> REFL51I is set to 200.

• ELP500 is enabled.

• The REFL51 demodulation phase is set to 130.100 deg.

Previously, this state only checked is_src1f_locked. Since the same state is now used for 3f locking, the is_src3f_locked condition was also added.

3. SRMI 1f/3f commissioning

[PREP_FM_FOR_SRMI]

• The HWP angle is set to 140 deg.
• The demodulation phase is set to:  1f: -149.60 deg, 3f: 70.100 deg
  For 1f locking, MICH and SRCL are sensed using POP17Q and POP17I, respectively. Considering that the SRCL signal may be larger than the MICH signal, the demodulation phase was adjusted to minimize the SRCL contribution in POP17Q.
• For both 1f and 3f locking, the output matrix elements from MICH to BS and SRM are configured. MICH -> BS is already set to 1 by default. In this state, MICH -> SRM is additionally set to 0.23479. This value was estimated from the theoretical ratio and measured responses of BS and SRM during SRX commissioning, in order to predict the coupling between MICH and SRCL in SRMI. With this setting, the SRMI control loops were stable after lock acquisition. This is the same approach as that used when transitioning from PRY to PRMI in klog37812.

[LOCKING_SRMI]

• The default input matrix elements configured in the DOWN state are cleared before setting the SRMI input matrix.
  For SRMI 1f, the following elements are set: LSC_INMTRX['MICH','POPA17Q'] = 57.5, LSC_INMTRX['SRCL','POPA17I'] = 13.335
  For SRMI 3f, the following elements are set: LSC_INMTRX['MICH','REFL51Q'] = -176.4, LSC_INMTRX['SRCL','REFL51I'] = 66.976
• For both 1f and 3f locking, the following settings are applied:

  • MICH2: ELP100 ON and ELP500 OFF.

  • SRCL2: ELP500 ON.

  • MICH1 gain: 0.081.

  • SRCL1 gain: 0.297.

  • When the interferometer approaches resonance, the SRCL2 and MICH2 gains are set to -0.1 and 60, respectively.

• Previously, only is_srmi1f_locked was used to check the lock status. The is_srmi3f_locked condition was added to support SRMI 3f locking.

[SRMI_3F_LOCKED]

• The @check_srmi3f decorator was added to monitor the SRMI 3f lock status.

[Ushiba, Hirose, Kataoka, Sugioka]

Abstract:

We performed adjustments for SRMI 1f and 3f. SRMI1f adjustments were conducted in the same way as PRMI(klog 37812).
Then SRMI3f lock was achieved by copying the control conditions from that of 1f.

Details:

SRMI 1f

We achieved SRMI 1f locking,and completed the phasing, decoupling, calibration, and UGF adjustments for SRMI 1f.

First, we performed the phasing and gain adjustment for SRX(Figure.1).
We changed ELP500 filter to ELP100 in order to avoid the output signal saturation, and SRX was succesfully locked.

Next, we locked SRMI 1f and performed the phasing for POP17 by injecting a 110.125 Hz excitation into K1:LSC-SRCL1_EXC. 
We tuned the demodulation phase to minimize the peak in POP17Q(Figure.2). 

Then, we addressed the decoupling between SRCL and MICH. These channels exhibit an inherent MICH-to-SRCL actuator coupling. 
This cloupling is originated from using only BS as the MICH actuator, since moving BS inherently causes fluctuations in SRCL as well. 
To eliminate this fundamental actuator coupling, we decoupled the actuators by adjusting the output matrix. 
The value to be set in K1:LSC-OUTPUT_MTRX_6_1 represents the ratio of the SRCL length fluctuations caused by BS versus SRM. The actuator efficiencies were measured by taking transfer functions from excitations of SRM and BS to the SRX length with SRX locked(Figure.3). Since the difference between these responses was -6.586 dB, a value of 0.23479—accounting for an additional factor of 2 due to the difference in the BS position's impact on SRCL and SRY—was entered into K1:LSC-OUTPUT_MTRX_6_1.

We then performed OLTF measurements for calibration and UGF adjustments. Sensor calibration was conducted while monitoring the Out-to-In TF, whereas UGF adjustments were made by monitoring the OLTFs, for both MICH and SRCL(Figure.4,5). During the sensor calibration, we updated the INMTRX values and simultaneously adjusted the filter gains to maintain the overall control gain. For the UGF adjustment, we fine-tuned the filter gains,resulting in a UGF of ~20 Hz for MICH and ~40 Hz for SRCL. 

SRMI 3f

For SRMI 3f, we performed the phasing for REFL51 while SRCL1f was locked(Figure.6), and we copied the control conditions from SRMI1f.
We measured the TF from POP17I/Q-to-REFL51I/Q while exciting SRCL/MICH at 110.125Hz(Figure.7,8). 
Then we multiplied the inverse of TF gain to 1f-INMTRX in order to make the 3f-INMTRX.
Measured TF gain for I/Q was -14.374dB/-9.735dB, so we set 3f-INMTRX for SRCL/MICH 66.976/176.4 while 1f-INMTRX was 13.335/57.5.
We put -1 gain filter in MICH1 FM2 because the phase of TF POP17Q2REFL51Q was ~180degree.
Since the control condition for 3f is exactly the same as that of 1f, SRMI 3f control was achieved and OLTF measurement matched to that of 1f very well(FIgure.9,10).

All of these parameter changes were updated in Guardian,and the specific Guardian modifications will be detailed in Hirose-san’s upcoming post.

Here is a brief summary of the procedure for PRMI 3f locking.

First, we attempted to switch from PRMI 1f to 3f locking by adding the 3f signal ratios measured during 1f locking to the INMTRX. However, we could not achieve stable 3f locking with this method.

Therefore, we restored the gains, INMTRX, and demodulation phases to the settings that had successfully achieved PRMI 3f locking earlier in the morning. We also applied the same OUTMTRX settings as those used for PRMI 1f locking. With these settings, we successfully locked PRMI 3f.

After achieving the lock, we readjusted the demodulation phases (FIG1 and FIG2).

The OLTF measurements and decoupling adjustments are described in Sugioka-kun's klog37812.

These settings have been implemented in the Guardian, as described in klog37813.

This is a summary of the Guardian modifications described in klog 37812.

1. Changes to the Guardian paths

• The original path between DOWN and LOCK_PREP_FOR_OBSERVATION has been disconnected. This path was previously used for the transition from DOWN to PRMI_3F_LOCKED. The observation path in the VERTEX Guardian will be modified for DRMI locking in the future. The settings in the DOWN state have not been changed. The parameters used for PRMI 1f/3f locking are reset in the DOWN state. PRMI_3F_LOCKED can now be reached from LOCKING_PRMI, which is on the path DOWN → LOCKING_PRMI → PRMI_1F_LOCKED. The settings in LOCKING_PRMI are now selected depending on whether PRMI 1f or 3f locking is requested.

2. Changes to each state

[PREP_FM_FOR_PRMI]

• [Demodulation phases] The demodulation phases are set separately for PRMI 1f and 3f locking. For each degree of freedom, the demodulation phase was optimized so that the signal appears mainly in either the I or Q phase. Previously, the demodulation phases were adjusted for MICH and PRX 1f/3f locking. This time, the phases were re-optimized under PRMI locking conditions, and the values were updated accordingly.
• [Output matrix] The OUTMTRX coefficient was set to -0.0404 to send the MICH feedback signal to BS and PRM. The same coefficient is used for both PRMI 1f and 3f locking.

• [HWP setting] During PRMI 3f locking, the REFL optical power was too high. Therefore, the HWP angle was changed from 140 deg to 160 deg. The HWP is now set to 160 deg in this state.

[LOCKING_PRMI]

The input matrix and feedback gains are configured according to the requested locking mode.

For PRMI 1f locking (PRMI_1F_LOCKED request):

• INMTRX:

  • POP17Q, POP45I → MICH

  • POP45I → PRCL

• The gains of MICH1 and PRCL1 are applied first.

• Once the signals exceed the thresholds, the gains of MICH2 and PRCL2 are applied.

For PRMI 3f locking (PRMI_3F_LOCKED request):

• INMTRX:

  • REFL51I → MICH

  • REFL51I, POP135I → PRCL

• The gains of MICH1 and PRCL1 are applied first.

• Once the signals exceed the thresholds, the gains of MICH2 and PRCL2 are applied.

The same filters are used for both PRMI 1f and 3f locking.

[PRMI_3F_LOCKED]

• This state is now connected to LOCKING_PRMI. Previously, it was connected to LOCKING_PRMI_FOR_OBSERVATION. The state index remains unchanged.

[PRMI_3F_LOCKED_FOR_OBSERVATION]

• This is the former PRMI_3F_LOCKED state, which was connected to LOCKING_PRMI_FOR_OBSERVATION. The state index was changed from 450 to 460.

3. Current status

• PRMI 3f is currently locked using the VERTEX Guardian with the PRMI_3F_LOCKED request. At the same time, PRMI ADS is requested through the ASC_LOCK Guardian. The interferometer remains stable under these conditions. The Initial Alignment Guardian has not yet been tested. The HWP settings used in the PRMI path of the Initial Alignment Guardian and the VERTEX Guardian are identical. Therefore, no conflict due to the HWP settings is expected.

[Ushiba, Hirose, Kataoka, Sugioka]

Abstract:

We performed adjustments for PRMI 1f and 3f. Details regarding the PRMI 3f locking and phasing will be posted separately by Hirose-san.

Details:

PRMI 1f

For PRMI 1f, we completed the phasing, decoupling, calibration, and UGF adjustments.

 First, we performed the phasing for POP17 and POP45 by injecting a 100.125 Hz excitation into both K1:LSC-MICH1_EXC and K1:LSC-PRCL1_EXC. 
We tuned the demodulation phase to minimize the peaks in POP17Q and POP45I, which resulted in changing K1:LSC_POP_PDA1_RF17_PHASE_R from -141.0 to -96.0(Figure.1). 
The initial value for K1:LSC_POP_PDA1_RF45_PHASE_R (57.870) was found to be already optimized.

Next, we addressed the decoupling between PRCL and MICH. These channels exhibit sensor coupling alongside an inherent MICH-to-PRCL actuator coupling. 
The PRCL-to-MICH sensor decoupling was conducted by entering an appropriate value into K1:LSC-PD_DOF_MTRX_3_11. 
This value corresponds to the ratio of the peak heights in POP17Q and POP45I when exciting PRCL at 100.125 Hz.
The upper left pad in Figure.2 shows the spectrum of MICH signal before and after MTRX adjustment.

Coupling between the MICH and PRCL actuators was also observed, which originated from using only BS as the MICH actuator, since moving BS inherently causes fluctuations in PRCL as well. To eliminate this fundamental actuator coupling, we decoupled the actuators by adjusting the output matrix. The value to be set in K1:LSC-OUTPUT_MTRX_5_1 represents the ratio of the PRCL length fluctuations caused by BS versus PRM. The actuator efficiencies were measured by taking transfer functions from excitations of PRM and BS to the PRY length with PRY locked(Figure.3). Since the difference between these responses was -22 dB, a value of -0.0404—accounting for an additional factor of 2 due to the difference in the BS position's impact on PRCL and PRY—was entered into K1:LSC-OUTPUT_MTRX_5_1. We skipped the MICH-to-PRCL sensor decoupling because it was already sufficiently decoupled.

We then performed OLTF measurements for calibration and UGF adjustments. Sensor calibration was conducted while monitoring the Out-to-In TF, whereas UGF adjustments were made by monitoring the OLTFs, for both MICH and PRCL(Figure.4,5). During the sensor calibration, we updated the INMTRX values and simultaneously adjusted the filter gains to maintain the overall control gain. For the UGF adjustment, we fine-tuned the filter gains,resulting in a UGF of ~20 Hz for MICH and ~40 Hz for PRCL. 

All of these parameter changes were updated in Guardian,and the specific Guardian modifications will be detailed in Hirose-san’s upcoming post.

PRMI 3f

For PRMI 3f, we performed the decoupling, calibration, and UGF adjustments following the exact same procedure used for 1f(Figure.6,7,8). MICH was sufficiently decoupled from PRCL so we didn't perform the decoupling.

Temps at EXC and EYC are lower by 1C, compared to those during O4c, although all heaters are operating at their max power.

At EXC, the air conditioner seems to work. We will turn it off. 

At EYC, we need to operate more FFUs to compensate for the temperature.

This log summarizes the Guardian modifications related to the commissioning work reported in klog37802 and klog37803.

[DOWN state]

Added the following command to reset the MICH1 filter gain: self.FILT_MICH1.ramp_gain(1, 1, False)

### MICH 1f/3f locking

[PREP_FM_FOR_MICH]

• Set the HWP angle (IFO_REFL) to 140 deg.

• Set the following demodulation phases:

  • REFL_PDA2_RF51: 85.1 deg

  • POP_PDA1_RF17: -141.00 deg

[ENGAGE_MICH_3F]

The Guardian sequence branches into MICH 1f and MICH 3f locking after this state.

• Set the MICH1 filter gain depending on the requested state:

  • MICH 1f: 1.8

  • MICH 3f: 5.2

• Explicitly set the MICH input matrix (INMTRX) according to the requested locking configuration:

  • MICH 1f: POPA17Q

  • MICH 3f: REFL51Q

  Although REFL51Q was already selected in the DOWN state, the input matrix selection is explicitly performed here.

• In klog37802, we reported that the FB8 (z1p0.1) filter had been disabled to stabilize the MICH lock. However, after adjusting the HWP angle, the lock became stable with this filter enabled. Therefore, FB8 remains enabled in this state.

[MICH_1F_LOCKED, MICH_3F_LOCKED]

• Commented out the @check_mich decorator.

### PRX 1f/3f locking

[PREP_FM_FOR_PRC]

• Set the HWP angle (IFO_REFL) to 140 deg.

• Set the following demodulation phases:

  • REFL_PDA2_RF135: 31.200 deg

  • POP_PDA1_RF45: 57.870 deg

[LOCKING_PRC_3F]

The Guardian sequence branches into PRX 1f and PRX 3f locking after this state.

• Set the PRCL1 filter gain to 1.4 when PRX_3F_LOCKED is requested.

[PRX_3F_LOCKED]

Modified the threshold monitoring channel used by the @check_prc3f decorator:

• Previous channel: POP_PDA2 (DC)-->>New channel: POP_PDA2_RF90

When PRC is locked with the 3f signal, the POP_PDA2 DC power decreases. Since the previous threshold was set to detect values above a certain level, it was not suitable for monitoring the PRC 3f lock.

Therefore, we decided to use POP_PDA2_RF90 instead.

### PRMI locking

[PREP_FM_FOR_PRMI]

Added the demodulation phase settings optimized during the MICH and PRX commissioning:

• ezca['LSC-REFL_PDA2_RF51_PHASE_R'] = 85.1    # MICH 3f
• ezca['LSC-POP_PDA1_RF17_PHASE_R'] = -141.00   # MICH 1f
• ezca['LSC-REFL_PDA2_RF135_PHASE_R'] = 31.200  # PRCL 3f
• ezca['LSC-POP_PDA1_RF45_PHASE_R'] = 57.870    # PRCL 1f

These settings have not yet been tested for PRMI locking. If they are found to be inappropriate, please comment out these lines.

I have started cleaning up the VERTEX guardian to improve its readability and maintainability.

Today, I modified the LOCK_PREP state based on the following concepts:
1. Request the LOCK_ACQUISITION state for the IMMT1, IMMT2, PR2, PR3, BS guardians, regardless of the requested state of the VERTEX guardian.
2. Request the MISALIGNED_BF state for ITMX or ITMY when the VERTEX guardian attempts to lock PRX/SRX or PRY/SRY.
3. If 3f signals are used for IFO lock, the guardian does not manage the states of the ETM guardians.
4. Request the LOCK_ACQUISITION state to SR and OMMT guardians when the VERTEX guardian attempts to lock the SRC.
5. For PRMI, SRMI, and DRMI lock, request the MISALIGNED state for the OSTM guardian to avoid strong flashes of OMC.
6. Request the MISALIGNED_FOR_LOCK_ACQ and MISALIGNED state for the PRM and SRM guardians, respectively, when those suspensions are not required for the requested IFO lock.

Since I haven't tested the modified VERTEX guardian, there may still be some bugs.
So, if you encounter any problems in the LOCK_PREP state of the VERTEX guardian, please check the updated script or let me know.

[Ushiba, Sugimoto, Yokozawa, Hirose]

1. OMC lock recovery

Initially, the OMC was unable to lock. An investigation revealed that the CLC_GAIN value for the OMC PZT (LSC) dither had been set to 0. After enabling it, the OMC was successfully locked.

2. MICH 3f lock commissioning

We first attempted to lock PRMI, but the lock was unsuccessful. Therefore, we switched to MICH locking.

Since MICH locking will also be required for future CAL measurements, we checked whether MICH could be locked by requesting the corresponding state through the VIRTEX Guardian.

Initially, MICH 3f could not be locked. We made the following adjustments:

1. Dark offset removal

   • Removed the dark offsets from REFL51 I/Q and POP17 I/Q.

2. Demodulation phase adjustment

   • Roughly adjusted the REFL51 demodulation phase while monitoring the signals with ndscope, so that the I-phase signal was minimized.

3. Filter adjustment

   • The feedback signal showed large fluctuations and high-frequency noise in ndscope. We changed the low-pass filter from ELP500Hz to ELP100Hz.(The lamp time for these filters was set to ‘Immediate’.)

4. Guardian adjustment

   • Removed the threshold decorator used in the MICH locking sequence.

5. Low-frequency gain adjustment

   • Although the MICH resonance could be caught, the lock was unstable and the loop gain appeared to be low. So we removed the Lowpass(z1p0.1) filter. After this change, the MICH lock became stable.

6. Optical gain recovery

   • Measured the OLTF and found that the loop gain was still low. We adjusted the HWP(IFO-REFL) angle to 140 deg, where the Xarm power was maximized. The loop gain recovered after this adjustment.

3. MICH 3f calibration and UGF adjustment

Using the response of the BS actuator measured in the vertical (L) direction of OPLEV, the transfer function of MICH OUT2IN1 was calibrated to nm/cts. The BS longitudinal displacement is defined along the 45-degree direction. Therefore, when the BS moves by ($l_{\mathrm{BS}}$), the corresponding MICH displacement is $l_{\mathrm{MICH}}=l_x-l_y=\sqrt{2}l_{\mathrm{BS}}$.

The BS OPLEV longitudinal actuator response at 10 Hz was -127.96 dB in units of µm/cts. To convert this response to the MICH displacement in nm/cts, we applied the factor ($\sqrt{2}\times1000$), corresponding to
$20\log_{10}(\sqrt{2}\times1000)$=62.99 dB .
Thus, the MICH actuator response at 10 Hz is -127.96+62.99=-64.97 dB (nm/cts).

We measured the MICH OUT to IN1 transfer function and applied the calibration correction based on the difference between the measured response and the expected actuator response.
After calibration, we readjusted the MICH loop gain to achieve a UGF of approximately 20 Hz(Fig1). 
Finally, we carried out a phasing check and confirmed that REFL51 was at its minimum on Q phase.(FIg2)

4. MICH 1f lock commissioning

We also tested MICH 1f locking.

Unlike MICH 3f, MICH 1f was successfully locked simply by requesting the corresponding Guardian state, without additional adjustments.

We measured the OLTF and confirmed that the OUT2IN1 transfer function was consistent with the expected calibration in nm/cts.

Finally, we adjusted the MICH loop gain to achieve a UGF of approximately 9 Hz(FIG3), following the previous settings reported in klog29949 and klog29950.
Following the same procedure as on the 3f, we carried out a final phasing check and confirmed that POP17 was at its minimum on Q.