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.