1. I installed a seismograph on ITMX length oplev. (Fig 1)
2.We recalibrated the MN length oplev and PF length oplev in ITMX.As a result of readjustment, the Pitch signal no longer appears in LEN VER. (Fig 2 & Fig 3)
3.I have investigated the relationship between the position of the beam spot on the QPD and the effect of noise on OpLev.Measurements were made using ITMX PF length oplev and MN length oplev and varying HOR values of 0, 100, and 200.After the measurement was completed, I performed the length oplev QPD centering.
Seismometer information:
(CH1)X axis direction
K1:PEM-PORTABLE_IYC_RACK_IY0_ADC0_DSUB5_OUT_DQ
(CH2)Y axis direction
K1:PEM-PORTABLE_IYC_RACK_IY0_ADC0_DSUB6_OUT_DQ
(CH3)Z axis direction
K1:PEM-PORTABLE_IYC_RACK_IY0_ADC0_DSUB7_OUT_DQ
Fig.1. showed the spectrum for installed seismometer and BS/IXV seismometers.
When we adjusted the position of MN L QPD and PF L QPD, we excited.
0.35 Hz MNP 10 cnt (For MN L QPD)
1.62 Hz BFL 10000 cnt (For PF L QPD)
We removed the accelerometers that had been installed to investigate and characterize the length sensing oplevs for MN and PF stage.
Then, we performed the centering of MN/PF oplevs.
I found a questionable and interesting glitch (the channel is K1:VIS-MCI_TM_WIT_P_DQ) in the middle of night.
It seems that it wasn’t caused by human or earthquake.
[Details]
It has been known for a long time that glitches appear in MC oplevs, but the causes and trend of these glitches have not been identified yet. So, I decided to investigate them.
The date this glitch occurred is around 2021-09-26 16:55 UTC. This glitch has three interesting points.
First, there is a jump between before and after the glitch as shown around t = 7h in Fig1. The average of wave form is clearly changed.
Second, investigating the signals of various seismometers, it seems that it wasn’t caused by earthquake because there aren’t the glitches below 1Hz like earthquake, but above 1Hz in any seismometers as shown in Figs2-5 which represent the classified bands RMS from each seismometer (The Figs are Fig2: EXV, Fig3: EYV, Fig4: IXV, Fig5: MCF.). And then, these seismometers are separated each other. But nevertheless, the glitches in these signals occurred simultaneously. It is interesting.
Finally, it occurred in the middle of night, so it seems that it wasn’t caused by human.
So, it is worth investigating more. I want to advance the investigation, for example investigating other channels at same time, analyzing on Time-Frequency plane or Q-transform.
