Fig.1. showed the spectrum during down state (solid : opened IR shutter and IMC locked, dash : closed IR shutter).
Even in DOWN state, the spectrum have similar behavior.
Fig.2. showed the spectrum during the PRFPMI 3F locked state.
The interesting point is 18 Hz, both the spectrum of the voltage monitor and AS_PDA1_RF17 have large peaks.
Fig.3. showed the spectrum during the PRFPMI RF locked state.
There are three peaks(9, 13 and 18 Hz) in several spectrum.
Fig.4. showed he spectrum during the PRFPMI OMC DF readout state.
Those peaks were disappeared.
Fig.5. showed the time series for several channels. (IFO is LOCK_PREP state.)
With the fringe of MICH signal in AS, the voltage monitor also fluctuated.
Fig.6. showed the time series for several channels. (IFO is around RRMI 3f locked, before the handover.)
The fluctuation of the voltage monitor seems have some coherence with AS_PDA1_RF17 signal.
The high coherent channels are
K1:PEM-VOLT_OMC_RACK_DC_P18_OUT_DQ
K1:PEM-VOLT_OMC_RACK_DC_M18_OUT_DQ
K1:PEM-VOLT_OMC_CHAMBER_DIFF_OUT_DQ
K1:LSC-AS_PDA2_RF34_Q_ERR_DQ
K1:VIS-ITMY_MN_DAMP_T_OUT_DQ
(And K1:VIS-ITMY_MN_OSEMINF_H3_IN1_DQ)
I checked the OMC VOLT monitor channel and found that the ground level was changed suddenly on Oct. 27 13:20 JST with very large glitches (fig1).
I'm not so sure this phenomena related to the current DARM noise situation but it might be a hint to find the problem.
On Oct. 27, the work of OMC leak test, PEM injection, and interlock for EX GV were performed.
Many people joined open campus of ICRR and NAOJ, only small number of people worked at that time.
So, if you have any notices, please let us know.
Note:
On that day, we had a short power outage one hour after the glitches.
So, it might be due to just thunders around Kamioka area.
