ETMX oscillation problem was happened again (klog23377).
To identify the problem is coming from ETMX, I performed the same modification again as reported in klog23377 (from 23:05 JST).

So, please keep this condition for a while.

Today's oscillation in ETMX P seems to be 7.4Hz (The 1st picture) which is ~ a half of 15Hz. 

Even if this change of state (OBS -> Lock Acquisition) was done, this 7.4Hz oscillation exists at the level of ~ +/-0.02urad. However, it sometimes vanished around 23:30 (the second picture shows the shift of "without" oscillation and "with" oscillation ).

Around am 9 on 30th Dec, there seems to be a small earthquake-like ground excitation. Coherently, the FPMI got ~2Hz oscillation.

According to the Yaw motions of suspensions as in the attached picture, BS, and all Type-As are excited by this ground excitation, and ETMX/Y motion keeps this oscillation up to now. Fortunately, this excitation seems to decrease very gradually.

On the other hand, there is no Pitch excitation in BS because of this ground motion excitation. While all I/ETMX/Y are also excited in Pitch.

(around 17:30)

• (1st Picture) Sometimes, there seems to be a large 0.3 Hz motion (0.15 drops from 0.9) in LSC-TR_GRY_NORM_OUT_DQ. While no such large 0.3Hz motion in X(LSC-TR_GRX_NORM_OUT_DQ). Also LSC-TR_IRY_NORM_OUT_DQ is fluctuating around 0.9 ~ 0.98. Y-arm alignment seems not so be good. Or, does the microseismic noise mitigation control have a problem? 
• (2nd Picture) VIS-ETMY_TM_WIT_P_DQ sometimes large 1.6 Hz excitation at the level of 2 urad_pp. This could be the source of the FPMI unlock ??
• 3rd picture and 5th picture shows the relation of 1.6Hz oscillation in VIS-ETMY_TM_WIT_P_DQ and MN(VIS-ETMY_MN_WIT_P_DQ) where glitch noises disapperaed and appeared. 4th picture shows much fewer glitch noises in MN(VIS-ETMY_MN_WIT_P_DQ) and TM(VIS-ETMY_TM_WIT_P_DQ). So, The 1.6Hz amplitude is clearly related to the glitch noises in MN. This 1.6Hz excitation due to glitch noises in MN clearly affected on the LSC-TR_IR/GRY_NORM_OUT_DQ. This could be the reason why the FPMI is unlocked now.

Even if there was no glitch in ETMY MN, the FPMI was unlocked. So, this seems not to be the main reason for unlocking. While TR-GRY is now fluctuating around 0.8 and 0.9 for TR-IRY.

So bad alignment in Y-arm may be the unlocking reason.

The auto relock of FPMI after the down seemed to be reliably successful today!

7.4Hz in VIS-ETMX_TM_WIT_P was excited a lot just after the LSC "Observation state" even if the EX was set in "Lock Acquisition state". This is the main reason for unlocking now.

VIS-ETMY_MN_WIT_P_DQ values seem to have bistable values, one is around -98, the other is -92. The glitches seem to be the rapid jumping shift between these two values. 

Another component laser with a different wavelength? Another polarization component? Trouble in a battery part? I forget the test result by Yokozawa-kun team.

The IR/GR beam spots on ETMX seem to be right from the center.

The IR/GR beam spots on ETMY seem to be right/down from the center.

Figure 1 shows the Tcam image of ETMX and ETMY now.
As Miyoki-san pointed out beam spot on ETMX are off from the center, especially on ETMY.

Figure 2 shows the DARM control signals when FPMI was locked.
The oscillation frequency is about 7.5 Hz but also there is a beat of 0.07 Hz.
According to the suspension models of ETMX and ETMY, the frequency difference of pitch resonance around 7.5 Hz is about 0.07 Hz.
So, this excitation of ETMX might be coming from the ETMY resonance via the mass feedback.

To confirm kicking of ETMX is coming from IM or TM, I modified LSC_LOCK guardian to skip CHANGE_CROSSOVER_FREQUENCY at 9:23 JST.
Due to this modification, crossover frequency of TM-IM becomes about 3.5 Hz.
If the oscillation will stop, the origin of oscillation must be L2P coupling of ETMX IM stage.

After the reduction of crossover frequency, FPMI lock seems stable and lasts for 3 hours (fig1).
So, I changed ETMX to OBSERVATION state at 12:24 JST to check the stability of ETMX OBSERVATION state.
Also, I restored the change of LSC_LOCK guardian reported in klog23423.

Maybe because of an earthquake around 16:00, EX became "isolated state". I set it again to "lock acquisition". GRX resonance could be recovered.