The Brazilian spherical detector: progress and plans

Abstract

We are building the Schenberg gravitational wave detector at the Physics Institute of the University of São Paulo as programmed by the Brazilian Graviton Project. The antenna and its vibration isolation system are already built, and we have made a first cryogenic run for an overall test, in which we measured the antenna mechanical Q (figure of merit). We also have built a 10.21 GHz oscillator with phase noise performance better than −120 dBc at 3.2 kHz to pump an initial CuAl6% two-mode transducer. We plan to prepare this spherical antenna for a first operational run at 4.2 K with a single transducer and an initial target sensitivity of h ∼ 2 × 10−21 Hz−1/2 in a 50 Hz bandwidth around 3.2 kHz soon. Here we present details of this plan and some recent results of the development of this project.

Developments in resonant-mass detectors

“…• The possibility of obtaining large pieces of material suitable for a spherical detector has been investigated. Large pieces of CuAl alloys, with high quality factors [43,44], can be built. • The results obtained with the MiniGRAIL detector allowed us to test techniques useful for a large spherical antenna.…”

A physical criterion for validating the method used to design mechanical impedance matchers for Mario Schenberg's transducers

“…"Mario SCHENBERG" [1,2,3,4,5] is a spherical resonant-mass gravitational wave (GW) detector weighting 1.15ton, being built in the Department of Materials Physics at the University of Sao Paulo (Brazil). The sphere, with 65cm in diameter, is made of an alloy with 94% copper and 6% aluminum (94%Cu-6%Al).…”

Development of a SQUID Readout System for the MiniGRAIL

“…Similar detectors are under construction in São Paulo [4] and in Rome. Recently, the CuAl 6% sphere that is used in the MiniGRAIL was replaced.…”