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T: Fachverband Teilchenphysik

T 39: Gravitational Waves II

T 39.4: Talk

Tuesday, March 17, 2026, 17:00–17:15, KS 00.005

Newtonian Noise in non-spherical caverns for the Einstein Telescope — •Valentin Tempel, Jörg Pretz, and Achim Stahl — III. Physikalisches Institut, RWTH Aachen

The Einstein Telescope (ET), a proposed third-generation gravitational-wave detector, aims to exceed the sensitivity of current interferometers, enabling the observation of significantly fainter signals. Achieving the desired performance requires a precise understanding and likely also mitigation of Newtonian Noise (NN), which is expected to be a significant contribution to the ET noise budget in the 1-10 Hz region. One important NN component originates from seismic-induced density fluctuations in the surrounding rock, as well as from the motion of cavern walls, producing fluctuating gravitational forces on the interferometer test masses. In the past, simplified models with spherical caverns have often been used as a theoretical order-of-magnitude estimation for NN, but those models are not generally representative of realistic underground environments. We present how cavern geometry affects the coupling of NN from seismic waves to the ET mirrors. Using analytical and numerical methods, we quantify how deviations from spherical symmetry and variations in cavern size modify the NN coupling transfer functions. The results highlight the limitations of simplified models and emphasize the importance of accurate models for reliable NN predictions in the Einstein Telescope.

Keywords: Einstein Telescope; Gravitational Waves; Newtonian Noise; Seismic Noise; Gravitational Field