Detection of Impulsive. Monochromatic and Stochastic Gravitational Waves With Resonant Antennas

The sensitivity of a gravitational wave resonant detector for various types of waves is given in terms of the detector noise spectrum Sh(w). It is shown that for g.w. short bursts the sensitivity is determined by Sh(w)/dn, where dn is the detector bandwidth that depends strongly on the electromechanical transducer and associated electronics.The sensitivity for a g.w. stochastic background depends, at the detector resonance, only on Sh(w) that, in turns, for a given material, depends essentially on T/MQ, where T is the bar temperature, M is the bar mass and Q the merit factor. Thus a non sophisticated transducer with a bandwidth of a few Hz appears sufficient for measuring, at a particular frequency, the g.w. background.It is shown that the very nature of a resonant bar gives a good sensitivity at the resonance. A bar with M=2300 kg, Q=5 106, T=0.1 K and dn=0.9 Hz can detect a g.w. background with amplitude 7 10-23/*Hz. Cross-correlating for one hundred days two identical detectors installed in the same location, the sensitivity improves to 1.3 10-24/*Hz.