Virgo Logbook

B1_d3_ACp is now acquired at both 20 and 40 kHz, which allows for an easy check if we have any aliased lines. Fig 1 shows the ratio between the spectra of these 2 signals below 10 kHz. Some lines are visible as well as shape of the anti-alias filter of the channel acquired at 20 kHz (which does not seem to be really steep).

Fig 2 shows a zoom of a small line at 4375 Hz, which is a clear alias of a big line at 15625 Hz. Fig 3 shows a zoom around 9700 kHz, which shows that almost all the lines in the forest are actually aliases of lines just above 10 kHz. This confirms earlier conclusions of Irene and Michele that these are aliased mirror resonances.