The design of a new preisolator stage for the VIRGO superattenuator is pres
ented. The device is essentially a 6 m high inverted pendulum with horizont
al resonant frequency of 30 mHz. An isolation of 65 dB at 1 Hz has been ach
ieved. Very low forces are needed to move the whole superattenuator acting
on the inverted pendulum. For this reason, the system is a suitable platfor
m for the active control of the mirror suspension. (C) 1999 American Instit
ute of Physics. [S0034-6748(99)00805-9].