Studying the use of masses on the microwaves cables to isolate seismic noise in the Schenberg Detector. Carlos Frajuca Fábio da Silva Bortoli São Paulo Federal Institute  Nadja Simão Magalhães São Paulo Federal University Odylio D. Aguiar Space Research National Institute 19th GRG Meeting - 2010 08/02/09

Abstract A spherical gravitational wave (GW) detector has a heavy ball-shaped mass which vibrates when a GW passes through it. Such motion is monitored by transducers and the respective electronic signal is digitally analysed One of such detectors, SCHENBERG, will have resonant frequencies around 3.2 kHz with a bandwidth near 200 Hz. The frequencies of running detectors typically lay below 1 kHz, making the transducer development for this higher frequency detector somewhat more complex. Coaxial cables are use to carry microwaves to the Schenberg parametric transducers, but seismic noise is is transported with this cables as well. In this work the study of adding masses along this cables to minimize the seismic noise is show.

CHARACTERISTICS OF SCHENBERG Mass 1,15 ton Diameter 65 cm Alloy 94% Cu-6%Al

Sphere quadrupole modes © César A. Costa

Distribution of the microwave parametric resonant transducers

Two modes resonant transducer

Microwave cavity and resonator second mode 2 mm

Schematics of the detection system Directional Coupling Carrier Suppression Interferometer Band Pass Filter Raw Data

Cable dimension and remote mass (1/18 last stage of sphere suspension)

First case scenario

Response graph – 5 disks Seismic and response curves

Second case scenario

Response graph – 5 disks Seismic and response curves

Concluding Remarks This kind of suspension allows an attenuatioin of around 150db in m2/Hz.