1. 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
08/02/09

2. 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.

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

4. Sphere quadrupole modes
© César A. Costa

5. Distribution of the microwave parametric resonant transducers

7. Two modes resonant transducer

8. Microwave cavity and resonator second mode
2 mm

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

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

11. First case scenario

12. Response graph – 5 disks Seismic and response curves

13. Second case scenario

14. Response graph – 5 disks Seismic and response curves

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