Resonant transducers for a spherical Gravitational Wave antenna

TL;DR

This paper develops a theoretical framework for understanding the coupled dynamics of spherical gravitational wave detectors with resonant transducers, introducing new configurations and analyzing robustness to imperfections.

Contribution

It presents a novel power series approach to coupled sphere-transducer dynamics and proposes a new transducer arrangement called PHC, improving detector design.

Findings

The power series coupling scheme accurately describes system dynamics.

The proposed PHC configuration offers advantages over TIGA.

System characteristics are robust to small imperfections.

Abstract

Motion sensing in a spherical GW detector requires a multiple set of transducers attached to its surface at suitable locations. If transducers are of the resonant type then their motion couples to that of the sphere and the joint dynamics of the system has to be properly understood before reliable conclusions can be drawn from its readout. In this paper we address the problem of the coupled motion of a sphere and a set of resonators attached to it at arbitrary points. A remarkably elegant and powerful scheme emerges from the general equations which shows how coupling takes place as a power series in the small coupling constant ratio m(resonator)/M(sphere). We reasses in the new light the response of the highly symmetric TIGA and also present a new proposal (called PHC) which has less symmetry but which is based on 5 rather than 6 transducers per quadrupole mode sensed. We finally assess how the system charac- teristics are affected by slight departures from ideality, and find it to be quite robust to them. In particular we recover with full accuracy the reportedly measured frequencies of the LSU prototype TIGA.