The FPMI auto lock that seemed to be set in the last night kept failing on the process during GR -> IR control shift around 7 ~ 8 AM. ITMX kick was observed when the failure happened.
GRX is sometimes locked to LG01 mode. However, this is not the reason for the failures.
Earthquakes in this early morning occurred a lot of misalignment?
The GRX fiber noise canceling system seems to have excess noise around 40 Hz. It seems to spoil the transition from GR to IR.
One possibility could be the vibration of a water-cooling type beam dumper. Another is the FFU operation on the POP table.
Could PEM members please check the vibration on the optical table in the PSL room and POP table? One ~ two months trend is also effective to judge the relation of the operation timing of these dumpers.
Thank you for checking.
At that day, water chillar operation seemed starting (klog21845).
UTC 8:00 corresponds to 17:00. It is impossible to turn on HPL water chiller. In addition, the water chiller was not operated continuously until ~ 3 weeks ago. Miyakawa-kun turned off the chiller and HPL after his adjustments. until ~ 3 weeks ago.
Oh no, this event is more reliable reason to explain the ~40Hz noise excitation, orz. The timing and duration are perfect.
However, under this condition, FPMI was stabley lock-acquired before. So Another reason should exist.
The main reason of lock failure seems that the 40 Hz peak in ALS-X signals.
This peak didn't exist oin the morning of Oct. 17 and exsited in the evening of Oct. 18 (fig1).
So, the works at those days are suspicious.
I seemed to miss the setting of FFU rotation speed dial at ~3 but, actually at 7. It causes a sharp ratation noise fo fan around 40Hz and its higher/lower harmonics.
