Cryogenic system of the Rome group gravitational wave experiment

The main characteristics of a large cryostat constructed by the gravitational wave group of the University of Rome, to cool down to liquid helium temperature Weber-type gravitational wave antennas, 3 m long and weighing up to 5000 kg, are presented. The cryogenic system has the following features: continuous operation time with an interval of 1 day every 54 days to refill the cryostat; small temperature gradients in the experimental chamber where the antenna is located, and very high acoustic and seismic insulation giving attenuation of 250 dB at the antenna detection frequency of 900 Hz. The system, installed at CERN, is now operating. Using a FET amplifier, the antenna is able to detect gravitational wave bursts with a metric tensor perturbation at the earth of the order of $3 \times 10^{−18}$. Another order of magnitude will be gained by using a d.c. SQUID amplifier.