Some ADS of ETMY was something strange (cannot stop the good point), we need to check it later.
After that, we tried to lock the FPMI.
We changed the ITMY and ETMY from ALIGNED state to LOCK_ACQUISITION state
The fiber noise cancellation of the ALS_X can be locked, but in the state of the ALS DARM, the 2.5 Hz oscillation started, then lock loss happened.
So, 2.5 Hz oscillation reduction would be next step.
I did the same measurenet as klog 30416. The measurements were done with ALS CARM locked and ALS DARM open. I measured the transfer functions from {TM, IM, MN}_LOCK_L to DARM_OUT, and the results are shown in Figure1 (TM), Figure2 (IM), and Figure3 (MN). From these measurement I found
- Overall gain of TM control is different from the past measurement
- A sharp peak at 1.67 Hz
I noticed that in the previous measurement gain of TM_LOCK_L is 1.255, but now it's 1. I also found that FM4 of TM_LOCK_L is named "gain" and just multiplies 1.255, therefore it seems to be designed to implement the gain factor. I turned on this filter, and now I got almost the same results with the previous measurement as shown in Figure4. I also modified LSC_LOCK guardian not to turn off this filter.
After that, I tried to lock ALS DARM, but still 2.4 Hz oscillaiton grew up and lock was lost. Then, I measured the transfer function from TM_ISCINF_L to DARM_OUT as shown in Figure5 and Figure6. They looked similar, but I found that around 2.17 Hz and 2.45 Hz there are a narrow dip and thay may cause the instability.
We may need to tune the relative gain of the hierarchical control to reduce these dips.
Note
I remember that on 7/25 when we had the power outage at Mozumi office some setting related to ETMX was not recorded properly in SDF and reverted. Perhaps we are still missing other settings.
I made mistakes in putting wrong plots for TF from ETMX_TM_ISCINF_L (Figure5 & FIgure6). The proper plots are as attached.
