Large-scale Monolithic Fused-Silica Mirror Suspension for Third-Generation Gravitational-Wave Detectors

Abstract

Thermal noise from the suspension fibers used in the mirror pendulums in current gravitational-wave detectors is a critical noise source. Future detectors will require improved suspension performance with the specific ability to suspend much heavier masses to reduce radiation pressure noise, while retaining good thermal noise performance. In this paper we propose and experimentally demonstrate a design for a large-scale fused-silica suspension, demonstrating its suitability for holding an increased mass of 160 kg. We demonstrate the concepts for improving thermal noise via longer suspension fibers supporting a higher static stress. We present a full thermal noise analysis of our prototype, meeting requirements for conceptual third-generation detector designs such as the high frequency interferometer of the Einstein Telescope, and closely approaching that required for Cosmic Explorer.