A new capacitive read-out for EXPLORER and NAUTILUS

We describe the present status of a new read-out for the EXPLORER and NAUTILUS gravitational wave detectors. The read-out is based on a double-gap capacitive transducer and a double-SQUID amplifier. The transducer has been tested at liquid helium temperature and a Q of 1.0.106 has been measured with a biasing field of 20 MV/m. The double- SQUID amplifier has been tested down to 2 K with a high-Q resonant input load, showing very good stability and energy resolution, of about 70. With the new read-out, NAUTILUS, cooled to 100 mK, could reach a peak sensitivity of 3 . 10-22Hz-½ and a bandwidth, at the level of 10-21Hz-½, of about 35 Hz.