Virgo Logbook

Looking at the spectrogram of the Pr_B1_ACp_diff23 channels, one can see many lines that decays after each lock acquistion, see first plot. They are exact multiples of the fundamental 8 hz lines, which is excited at the beginning of each lock. See first plot.

Since the harmonics are very well visible in the difference channels, they are very likely not generated by the ITF, but by some harmonic distorption inside the electronic (maybe the ADC?). Morevoer the d3 channel shows larger lines, see last plot.

The total harmonic distortion can be estimated to be aboput 76 db.