Master thesis and internship[BR]- Master's thesis : Towards the development of ultra-high performance inertial sensors for gravitational wave detection[BR]- Integration Internship

Abstract

The gravitational wave detectors must be isolated from the Earth’s constant vibrations to be able to sense low-frequency gravitational waves. The combined performances of passive and active isolation stages allow getting close to the target requirements in terms of seismic vibration isolation. A new active platform is currently designed. Its embedded inertial sensors measure the ground motion, which is then actively canceled by actuators. The inertial sensors require a large dynamic measurement range, which can be achieved by lowering the sensor resonance frequency while increasing the resonance frequency of internal modes away from the operational range. The leaf-spring suspension composing the gravity compensator system of a vertical inertial sensor, the Compact Interferometric Inertial Sensor (μVINS), is numerically and experimentally characterized. The end-purpose of the study is to extend the dynamic measurement range of that particular inertial sensor by evaluating the impact on its resonance frequencies of various parameters related to the leaf-spring suspension. Following the numerous studies, numerical and experimental, performed in the context of this work, design guidelines are devised, enabling the suspension to be tuned into a low resonance frequency quasi-zero stiffness mechanism. The μVINS design can be modified to be competitive with the already existing sensors, while being more compact. Optimizing the leaf-spring suspension length and clamping location enabled the resonance frequency to be decreased by one order of magnitude. The measurement bandwidth is thus also increased by one order of magnitude. With the capacity to measure lower frequency displacements, μVINS can feed a wider range of data to the active stage and ensure an effective low-frequency isolation.