Measurement of the Stray Light in the Advanced Virgo Input Mode Cleaner Cavity using an instrumented baffle

TL;DR

This paper reports on the deployment of an instrumented baffle in the Virgo input mode cleaner cavity, measuring scattered light distribution to improve stray light control in gravitational wave detectors.

Contribution

It introduces a new instrumented baffle technology and presents the first measurements of scattered light distribution within the cavity.

Findings

Measured scattered light distribution using the new device

Data collected during Virgo commissioning phase at 28.5 W laser power

Comparison of measurements with scattered light simulations

Abstract

A new instrumented baffle was installed in Spring 2021 at Virgo surrounding the suspended mirror in the input mode cleaner triangular cavity. It serves as a demonstrator of the technology designed to instrument the baffles in the main arms in the near future. We present, for the first time, results on the measured scattered light distribution inside the cavity as determined by the new device using data collected between May and July 2021, with Virgo in commissioning phase and operating with an input laser power in the cavity of 28.5~W. The sensitivity of the baffle is discussed and the data is compared to scattered light simulations.