[Ushiba, Komori]

We tryed to reduce the PR3 length using narrow-band damping from the OLDAMP length to BF, similar to what was done for PR2 as reported in the klog:30633.

Initially, we believed the resonant frequency was 0.43 Hz by counting the wave number in the time series data.
However, upon checking the spectrum of PR3_TM_WIT_L, we found that it was likely the translational mode (T) and that the correct resonant frequency for L is 0.48 Hz.
We implemented a 10% pass Butterworth filter around 0.48 Hz and compared the spectrum with this filter.

The magenta and blue dots and lines represent the spectra with and without the filter, respectively.
The total RMS (black) is smaller without the filter than that with the filter (brown), indicating that the current filter did not work well.

I will continue to attempt to reduce the RMS.
On the other hand, the RMS is below 0.3 μm even without the damping filter, which is close to the RMS of PR2 with the damping filter (0.2 um).
Therefore, the current RMS might already be small enough.