Angular control noise in Advanced Virgo and implications for the Einstein Telescope

TL;DR

This paper models the angular control noise in Advanced Virgo, demonstrating that it is not a limiting factor for the detector's sensitivity, and provides insights for the design of future gravitational wave observatories like the Einstein Telescope.

Contribution

We developed a detailed model of Advanced Virgo's angular control system that matches experimental data and assesses its impact on future detector sensitivity.

Findings

Virgo's angular control noise is not a limiting factor at full power.

The model accurately replicates the measured coupling between angle and length.

Implications for the Einstein Telescope's design and sensitivity are discussed.

Abstract

With significantly improved sensitivity, the Einstein Telescope (ET), along with other upcoming gravitational wave detectors, will mark the beginning of precision gravitational wave astronomy. However, the pursuit of surpassing current detector capabilities requires careful consideration of technical constraints inherent in existing designs. The significant improvement of ET lies in the low-frequency range, where it anticipates a one million-fold increase in sensitivity compared to current detectors. Angular control noise is a primary limitation for LIGO detectors in this frequency range, originating from the need to maintain optical alignment. Given the expected improvements in ET's low-frequency range, precise assessment of angular control noise becomes crucial for achieving target sensitivity. To address this, we developed a model of the angular control system of Advanced Virgo, closely matching experimental data and providing a robust foundation for modeling future-generation detectors. Our model, for the first time, enables replication of the measured coupling level between angle and length. Additionally, our findings confirm that Virgo, unlike LIGO, is not constrained by alignment control noise, even if the detector were operating at full power.