Progress in the development of a niobium gravitational radiation antenna

A 1.5 tonne gravitational radiation antenna is being constructed with the aim of detecting gravitational radiation pulses of amplitude ∼ 10-20, that may be produced by the gravitational collapse of stars in nearby galaxies. Two aspects of the project are discussed. Firstly, a progress report on acoustic loss measurements in niobium is given. Acoustic losses determine the Brownian noise limit to the antenna sensitivity. Secondly, a detailed analysis of parametric transducer design is summarised. It is shown that with a practically realisable system it is possible to achieve a system noise number ∼ 103, for a 1 metre long, 67 Kg bar. This corresponds to a noise temperature of ∼ 100 μK and a strain sensitivity of 8 x 10-19. For the 1.5 tonne antenna the noise number is ∼ 104 corresponding to a noise temperature of ∼ 500 μK and a strain sensitivity of 3 x 10-19. (Auth.)