The Instrumented Baffle at the Input Mode Cleaner of Advanced Virgo Plus: Four years of Successful Operation as a Monitor of Stray Light

TL;DR

The paper reports four years of successful operation of an instrumented baffle in Advanced Virgo Plus, demonstrating its effectiveness in monitoring stray light, laser stability, and alignment without disturbing interferometer performance.

Contribution

It presents the design, deployment, and long-term performance assessment of an instrumented baffle for stray light monitoring in gravitational wave detectors.

Findings

The instrumented baffle effectively monitors stray light and laser stability.

It does not introduce additional noise or disturbance to the interferometer.

The technology is suitable for large-scale implementation in future upgrades.

Abstract

The suspended end mirror of the input mode cleaner cavity in the Advanced Virgo Plus interferometer was equipped with an instrumented baffle in spring 2021, serving as a demonstrator of the technology in preparation for the installation of large instrumented baffles in the main arms of the interferometer. This baffle includes tens of sensors positioned near the mirror to enable monitoring of stray light within the cavity. In this contribution, we assess the performance and stability of the instrument after four years of operation. After introducing the main characteristics of the baffle, we study the distribution of stray light and show that the instrumented baffle can be used to monitor laser stability and alignment within the cavity. Finally, we assess the noise level during the final stages of the O4b commissioning to monitor the impact of the baffle, and conclude that the baffle does not introduce any additional disturbance to the normal operation of the interferometer.