New modeling of the stray light noise in the main arms of the Einstein Telescope

TL;DR

This paper provides an improved model of stray light noise in the Einstein Telescope's main arms, accounting for various optical effects and configurations to enhance sensitivity predictions.

Contribution

It introduces an updated analysis of stray light noise, including baffle effects, diffraction calculations, and non-ideal optical conditions for the Einstein Telescope.

Findings

Enhanced noise modeling with baffle clipping and diffraction effects

Analysis of non-ideal cavity conditions and mirror absorbers

Guidelines for design constraints to improve sensitivity

Abstract

Stray light represents a significant noise source for gravitational wave detectors, requiring an accurate modeling and mitigation to preserve the experiment's sensitivity. In this article, we present an updated and improved analysis of the stray-light induced noise in the Einstein Telescope main arm. The results presented here supersede previous studies taking into account a number of improvements, including baffle clipping effects, new numerical calculations for computing diffraction contributions and the influence of baffle edge serrations. Results are presented for both triangular and L-shaped configurations for the experiment. Furthermore, in the case of the triangular configuration, we examine non-ideal optical cavity conditions, such as beam offsets and misalignments, and the presence of point absorbers in the mirrors, which can increase scattered light noise. This can be translated into future stringent constraints on the design and operating parameters of the interferometer, thus facilitating to achieve its sensitivity targets.