Test mass suspension Q measurement and excess loss diagnosis for gravitational wave interferometers

or gravitational wave interferometers to work as planned, they must exhibit low levels of thermal noise. Thermal noise performance demands the test mass suspension in the detectors has unprecedentedly high quality factors Q for all of its vibration modes in the bandwidth of ;In addition to the internal friction of wire, suspension Q is also limited by many excess loss mechanisms resulting from cross coupling between the measured suspension mode and all other degrees of freedom in the system. They prevent the true Q value, limited only by wire's internal friction, from being revealed in measurements.;The noval feature of this work are following: we will present a precise test of the dissipation dilution effect against most of the foreseeable excess loss mechanisms under various tensions in different wire-test mass clamping schemes. We found that the dissipation dilution effect works very well at stress levels up to the breaking stress when excess loss is as low as ;We will develop a clear diagnosis for microslip sliding friction damping at the clamping contact. We will also discover that the classical model of thermoelasticity breaks down in wire under large tension: a new theory we developed can provide a better explanation for the measured data.;A major concern about this feature is the possibility that large tension may degrade suspension Q by degrading wire's internal friction. These need to be tested before implementation of the pendulum in the detectors.;Seven excess loss mechanisms will be examined in some detail. While a few of them may contribute at or close to the...