Suspension for the low frequency facility

We introduce the working principles of the VIRGO Low Frequency Facility (LF F), whose main aim is the measurement of the thermal noise in the VIRGO sus pension system. We evaluate the displacement thermal noise of a mirror, whi ch is an intermediate element of a double pendulum suspension system. This double pendulum will be suspended to the last stage of a VIRGO Super-Attenu ator (SA), the prototype VIRGO suspension system being tested at the Pisa s ection of INFN. In the proposed configuration, we evaluate the spectrum of the thermal noise for different choices of the parameters: based on this st udy, we comment on the future directions to be undertaken in the LFF experi ment. (C) 2000 Published by Elsevier Science B.V. All rights reserved.