Speaker
Description
Accurately predicting seismic Newtonian Noise (NN) for the Einstein Telescope remains a significant challenge. To determine whether a site-specific NN level is compatible with the target sensitivity of the Einstein Telescope (ET), it is essential to have a solid understanding of NN estimation and its planned mitigation. Validating numerical NN estimates requires careful consideration of three key aspects:
First, the simulated seismic field must be realistic and well understood for every corner point of the ET. This includes ensuring an appropriate composition of wave types as well as realistic source distributions. Additionally, the simulated seismic data must be consistent with measured seismic spectra both at the surface and underground. Second, when converting the seismic displacement field into forces acting on the mirrors, the geometry and physical properties of the surrounding environment, such as the rock density, the shape and distances of interfaces such as cavern walls, geological layers, and the Earth’s surface, must be thoroughly considered. Third, the forces acting on the mirrors must be translated into mirror displacements along the laser direction and ultimately into the NN strain. This step must also account for correlations between multiple mirrors and, in the case of the triangular ET design, between multiple detectors.
In this work, we present well-controlled test scenarios to ensure reliable NN calculations, focusing on the latter two steps of the modeling process. Our approach builds on previous analytical studies of NN coupling transfer functions by systematically varying mirror positions, cavern sizes and shapes, as well as the composition of the seismic field. Carefully validated numerical tools are essential, as they are needed to overcome the known limitations of simplified analytical approaches used in past preliminary NN estimates.