In the past days I spent some time to modify again the damping loops.

The main reason was that the loops that I have implemented before (see entry #1641) had the first UFG at too low frequency (<100 mHz) and it took to much time to change DC offset to align the cavity. Also I'm not sure if the signal in the 10-100 mHz corresponds to a real motion of the suspensions or is oplev noise.

In the attached PDF I report the new filter performances. I tried to avoid any overshoot but I think they can be further improved.

Some remarks:

- I observed that sometimes an eccess of noise shows up in the whole BS YAW spectrum when closing the BS PITCH loop. I have slightly decreased the BS pitch gain and it has disappeared.

- The pitch peaks just above 10 Hz are quite hard to damp as they are coming from the stack resonance. (See attached a plot of the spectrum of an oplev for a mirror placed directly on the stack.)