No abstract

The Mario Schenberg gravitational wave detector has been constructed at its site in the Physics Institute of the University of São Paulo as programmed by the Brazilian Graviton Project, under the full support of FAPESP (the São Paulo State Foundation for Research Support). We are preparing it for a first commissioning run of the spherical antenna at 4.2 K with three parametric transducers and an initial target sensitivity of h ∼ 2 × 10−21 Hz−1/2 in a 60 Hz bandwidth around 3.2 kHz. Here we present the status of this project.

Thermomechanical processing of low carbon bainitic steels is used to obtain a bainitic microstructure with good strength and toughness by continuous cooling after forging without the need of further heat treating, hence reducing manufacturing costs. However, hot forging parameters can significantly influence the microstructure in the forged material. A series of heat treating and forging experiments was carried out to analyze the effect of austenitizing time and temperature on the grain growth and the effect of forging temperature on the Prior Austenite Grain Size (PAGS) and continuously cooled microstructure. The forged microstructures were characterized by optical microscopy, microhardness tests, and X-ray diffraction. The results indicate that at 1200 °C austenitizing temperature abnormal grain growth takes place. Forging temperature significantly affects the PAGS and the subsequently formed microstructure. At high forging temperature (1200 °C), an almost fully bainitic microstructure was obtained. As the forging temperature was reduced to 1100 and 1000 °C, the PAGS refined, while the polygonal ferrite faction increased and the amount of retained austenite decreased. Further evaluations showed that a decrease in the forging temperature results in a higher carbon concentration in solution in the retained austenite leading to a stabilization effect.

No abstract

Here we present a status report of the first spherical antenna project equipped with a set of parametric transducers for gravitational detection. The Mario Schenberg, as it is called, started its commissioning phase at the Physics Institute of the University of São Paulo, in September 2006, under the full support of FAPESP. We have been testing the three preliminary parametric transducer systems in order to prepare the detector for the next cryogenic run, when it will be calibrated. We are also developing sapphire oscillators that will replace the current ones thereby providing better performance. We also plan to install eight transducers in the near future, six of which are of the two-mode type and arranged according to the truncated icosahedron configuration. The other two, which will be placed close to the sphere equator, will be mechanically non-resonant. In doing so, we want to verify that if the Schenberg antenna can become a wideband gravitational wave detector through the use of an ultra-high sensitivity non-resonant transducer constructed using the recent achievements of nanotechnology.