OPTIMAL SENSITIVITY FOR THE ULTRACRYOGENIC GW ANTENNA AURIGA

We report on a complete analysis of the noise sources in a ultracryoge nic bar working at T less-than-or-equal-to 100 mK, equipped with GHz b ias liquid helium cooled preamplifier r.f. SQUID. Optimal values for p arameters, as transducer mass, the coupling inductance, etc. are numer ically determined in order to get maximum sensitivity to impulsive gra vitational wave signals. The sensitivity is improved by selectively co oling the fundamental resonance. The Standard Quantum Limit is found t o be within reach of current cryogenic technology.