[en] A general analysis of the characteristics of a resonant transducer for gravitational-wave antennas whose resonator has a general mode of vibration has been made using a Lagrangian formalism. The method has been applied to investigate the characteristics of the resonant capacitive transducer developed at the University of Rome and mounted on the cryogenic gravitational-wave antenna built at CERN, finding results in good agreement with the experimental behaviour

[en] We studied how a holder used to suspend the mirrors of a gravitational wave interferometer, can influence the mechanical behavior and consequently modify the mirror thermal noise contribution to the detector sensitivity curve. The results are important to optimize the design for the PR mirror in the Virgo gravitational wave interferometer

[en] The research being performed at the University of Rome on transducers concerns two different kinds of resonant transducers: a capacitive transducer coupled to a low noise cooled FET amplifier and an inductive superconducting transducer coupled to a DC SQUID. Both types of transducer are briefly described. (Auth.)

[en] Measurements at T = 4.2 K of the mechanical-transfer function (m.t.f.) and of the Brownian noise of a small test antenna using a new type of suspensions are reported. These suspensions operate as a double mechanical filter and their m.t.f. has been measured in order to investigate their use for the big (5t) gravitational-wave antenna now being assembled at CERN by the Rome group. The experimental results are in good agreement with the expected values. (author)

[en] 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 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 x 10^-18. (author)

[en] We report on the results obtained with a cryogenic gravitational wave antenna equipped with a d.c. SQUID, operating at 2 K. During a period of a few days in April 1989 the measured noise temperature (for short bursts of gravitational waves) was T_eff ≅ 7 mK corresponding to a sensitivity of h_c ≅ 7 · 10^-19. This result allows to improve the previously published upper limits for the rate of gravitational wave bursts

[en] The analysis described in this paper, made on the bases of two a priori assumptions derived from the results of the authors' work, shows that the Kamioka data support the previously found correlation between the g.w. data and the Mont Blanc data. The probability that this support be accidental is of the order of 3.3 x 10^-4 or 4.7 x 10^-4 and, in all cases, it is smaller than 5.1 x 10^-3. To this, it should be added the fact that the Kamioka contribution is due to events concentrated near the 5νMont Blanc event

[en] The data collected in May 1980 with two gravitational-wave antennas operated simultaneously, one (M = 20 kg) in Rome, the other (M = 389 kg) in Frascati, show a few high-energy events recorded by the two stations at times which differ by a few seconds. The probability for these ''coincidences'' to be accidental is of the order of 10^-₄. Various considerations tend to exclude that these events are due to gravitational waves of extraterrestrial origin. In addition, a few types of trivial local disturbances have been excluded. A study of the occurrence times of the events recorded at Frascati shows the presence of two periods (T = 53.1 and 54.7 min) equal to those of the free oscillations of the Earth: ⁰S²⁺₁ and ⁰S^2-₁. (author)

[en] During the last years the Italian group interested in the search of gravitational waves (a collaboration between the University of Rome and the C.N.R.) has made a few experiments with small cryogenic antennas. Their purpose was, to measure the mechanical quality factor of the antenna, to test the magnetic suspensions, the electronic apparatus, the data acquisition system and finally to measure the Brownian noise by means of piezoelectric ceramics. For the first time in June 1978 the authors successfully cooled down to 4.2 K a larger aluminium bar, M=389 kg and resonance frequency 1795 Hz, equipped also with piezoelectric ceramics. This bar was cooled down again in May 1979. The main purpose was essentially to learn more about the mechanical filters for a proper design of the final large antenna, M=5000 kg. (Auth.)

[en] Thermal Noise is one of the limiting factor in the low and intermediate frequency range of the interferometric Gravitational Wave (GW) detectors. For beating this limit, a full scale last stage suspension (payload) prototype has been designed and built. Together with a mirror made of silicon, it has been cooled down at low temperature. Suspending the mirror from a cradle system, identical to that one used in the present VIRGO payload, the cooling strategy, the thermal behavior as well as the system mechanical response have been deeply studied. In this paper, the results obtained during the first cooling of the tested prototype are reported.