An Advanced Inductive Transducer For Resonant Mass Gravitational Wave Detectors

We report on the sensitivity of a transducer which uses a low noise SQUID amplifier. The transducer is made of niobium and was electropolished and heat treated to improve the Qs. The mechanical Q was found to be 3.15 x 10(6) at 4 K and the electrical Q was 2.52 x 10(5). With a low noise SQUID designed for this transducer, the noise temperature of the transducer was found to be 1.1 mK, of which 0.7 mK was due to the SQUID. This is about 200x larger than the expected noise from the SQUID. Noise from flux trapped on the chip is the most likely cause.