Progress report on the development of a very high sensitivity parametric transducer for the Mario Schenberg Gravitational wave detector

Abstract

We have constructed the Mario Schenberg gravitational wave detector at the Physics Institute of the University of Sao Paulo as programmed by the Brazilian Graviton Project, under the full support of FAPESP (the São Paulo State Foundation for Research Support). We are ready to do a first test run of the spherical antenna at 4.2K with three parametric transducers and an initial target sensitivity of h∼10−21Hz−½ in a 60Hz bandwidth around 3.2kHz. The parametric transducers to be used on the Mario Schenberg detector consist of reentrant klystron copper-aluminum cavities covered with a thin layer of niobium on the walls and on the oscillating membrane. The gap between the central conical post and the membrane is about 40µm. Here we present a progress report on this transducer development related with niobium layer deposition in the transducer cavities and on the design of silicon membranes for the last transducer mechanical mode.