Estudo do sistema de transdução paramétrica para detectores de ondas gravitacionais / Study of parametric transduction system for gravitational wave detectors


IBICT - Instituto Brasileiro de Informação em Ciência e Tecnologia




The search for gravity waves began in 60s with Weber. After 40 years we still dont have any experimental evidences of its existence. In spite of this, many research groups around the world are still working in this search. The possibility of detection of this kind of wave will open a new window to study the universe and that is a strong reason to justify all the investment in this research. We can classify the detector in two main kinds: Resonant Mass Detector and Laser Interferometer. In this work it is analyzed a kind of parametric transducer pumped by a microwave source at 10 GHz. This kind of transducer is used at the University of Western Australia (UWA) and will be used in the Brazilian Mario Schenberg detector. In this thesis the results obtained in the study of a type of parametric transducer are showed. The change of a cryogenic GaAs amplifier by a cryogenic HEMT was discussed. This change can produce a very low noise temperature for the system. We present a proposal for reducing the phase noise of a microwave oscillator as well. This oscillator is used to pump the transducer. We measured the electrical coupling of some micro strip antennas. With these antennas we prevent the cable connection to the mass antenna. This can reduce the seismic noise. We study a microwave superconductor niobium cavity, measuring its electrical Q as a function of the electrical coupling. Our intention is modify the Australian transducer from a re-entrant opened one to a reentrant closed one. We believe that with this change we can improve the electrical Q of the cavity. Finally, we show that is possible, with some modifications to improve the transduction system used at UWA and, with this, reach de Quantum Limit with the Brazilian detector.


ondas gravitacionais transdutores grávitons antenas microstrips redução de ruído

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