We need the confirmation, even the larger amplitude of the shaker (30 count -> 200 count) and longer measurement time (8s -> 16s), the coherence was small as shown in Fig.1. - Fig.4.
(The shaker vibrated about 1,000 times larger than background from the accelerometer which placed near the shaker)
We will compare more about the difference from previous measurement.
Even this measurement, we can confirm the linear coupling of the vibration(geophone) to DARM is 1/10 in current sensitivity.
I put the several spectrum in
https://dac.icrr.u-tokyo.ac.jp/KAGRA/DAWG/Detchar/klog/klog31535
All spectrums are placed in /users/Commissioning/data/OMC/2024/1108/pics/
In case of the previously, the amplitude of shaker was about 100 times larger than this measurement(Fig.1.).
(Clearly see the peaks in geophone and DARM)
The main difference would be we put the tape on the shaker(Fixing the shaker on the bellows strongly).
We will perform similar treatment and measure again.
Still there are low coherence in several frequencies, better measurement can be proformed.
Fig.1. showed the TF from OMC geophone to DARM (Red: this measurement, Blue: before OMC stack connection)
Fig.2. showed the TF from OMC LSC ERR to DARM (Red: this measurement, Blue: before OMC stack connection)
Fig.3 showed the linear noise projection based on this measurement
Red : DARM displacement today
Blue : noise projection from OMC geophone
Green : noise projection from OMC LSC ERR
Noise projection from OMC LSC ERR would not be correct if this spectrum was the sensor noise.
Looking at the Summary page, maybe the peaks at 120Hz (and 116Hz) would not grow up while doing the PEM injection to OMC? If correct, that might be good tendency...