By the way, there are many peaks around 180 Hz. Simply counting, the number of the peaks are 24? for me... Maybe some sprious peaks not related to the thermal dissipation would be mixed in, and such sprious ones should not be reduced by cooling the sapphire mirrors. So how can we distinguish these ones and those? Making a statistical number of spctrogram during silent run might be able to distinguish the peaks as such spurious peaks might sometimes disappear and sometimes appear maybe depending on the alignment of the interferometer(?)
We can find the analysis for O3GK as klog#14886. I don't know why the modes are not 4 x 4 = 16 for the sapphire fibers. Degeneracy?
Matched frequencies are not so much.
Thank you so much for making the comparison figure. Yes, I'm wondering what are these lower or upper peaks...
>I don't know why the modes are not 4 x 4 = 16 for the sapphire fibers. Degeneracy?
Maybe yes. Maximum numbers of violin modes are 4 fibers × 4 mirrors × 2 DoF in horizontal direction = 32.
If the mode shape of violin mode is purely aligned to L and T, one of them (mode aligned to T ditection) cannot be seen in DARM seisitivity.
However, since the mode is not aligned to L and T direction in reality, some of them might be seen in the DARM, so number of the peaks can be explained by violin modes (I don't think all of them are coming from violin modes, though...).
The eigenfrequencies are depending on each tension and can be changed by the weight balance.
So it is natural to be different from the O3GK.