The Brazilian gravitational wave detector Mario Schenberg: status report

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.

Nearby Stars as Gravitational Wave Detectors

“…Because stars have much larger masses than convectional resonant mass detectors, their integrated cross-section is many orders of magnitude larger. In the Sun, low order modes have a Σ n that is 17 or 20 orders of magnitude (if we consider the steady-state or undamped limits respectively) larger than the current detectors, such as Mario Schenberg (Aguiar et al 2006), Minigrial (Gottardi 2007) and Allegro (Mauceli et al 1996). Gottardi (2007) estimates a Σ n of the order of 9.8 10 −22 cm −2 Hz for a high performance resonant mass detector.…”

Gravitational Wave Detection by Interferometry (Ground and Space)

“…It seems unlikely that Weber was observing gravitational-wave signals because, although his detectors were very sensitive, being able to detect strains of the order of 10 -16 over millisecond timescales [309], their sensitivity was far away from what was predicted to be required theoretically. Development of Weber bar type detectors continued with significant emphasis on cooling to reduce the noise levels, although work in this area is now subsiding with efforts continuing on Auriga [88], Nautilus [238], MiniGRAIL [232,158] and Mário Schenberg [159,70]. In around 2003, the sensitivity of km-scale interferometric gravitationalwave detectors began to surpass the peak sensitivity of these cryogenic bar detectors (≃ 10 -21 ) and, for example, the LIGO detectors reached their design sensitivities at almost all frequencies by 2005 (peak sensitivity ≃ 2 × 10 -23 at ≃ 200 Hz) [314], see Section 6.1 for more information on science runs of the recent generation of detectors.…”

“…Following the lack of confirmed detection of signals, aluminium bar systems operated at and below the temperature of liquid helium were developed [252,260,76,170], although work in this area is now subsiding, with only two detectors, Auriga [88] and Nautilus [238], continuing to operate. Effort also continues to be pursued into cryogenic spherical bar detectors, which are designed to have a wider bandwidth than the cylindrical bars, with the two prototype detectors the Dutch MiniGRAIL [232,158] and Brazilian Mário Schenberg [159,70]. However, the most promising design of gravitational-wave detectors, offering the possibility of very high sensitivities over a wide range of frequency, uses widely-separated test masses freely suspended as pendulums on Earth or in a drag-free craft in space; laser interferometry provides a means of sensing the motion of the masses produced as they interact with a gravitational wave.…”

Summary: gravitation and cosmology

“…There are several worldwide experiments under operation, construction or design. Brazil has its share on this market, via the Schenberg detector, a spherical antenna, which, in its first commissioning run, will operate with three transducers, cooled to around 4 K and a target sensitivity of h ∼ 2 × 10 −21 Hz −1/2 in a 60 Hz bandwidth around 3.2 kHz [8]. Possibly the main advantage of this kind of spherical antenna is its ability to detect a gravitational wave from any direction and with arbitrary polarization.…”