Environmental Measurements in the Sedrun Access Shaft to the Gotthard Base Tunnel -- a Promising Site for a Long-Baseline Atom Interferometer

TL;DR

This study evaluates the Sedrun access shaft for atom interferometer experiments, finding low environmental noise levels suitable for detecting ultralight bosonic dark matter and gravitational waves.

Contribution

It provides the first environmental assessment of the Sedrun shaft as a potential site for long-baseline atom interferometry experiments.

Findings

Ground motion activity is low enough for AI operation.

Electromagnetic background levels are acceptable for sensitive measurements.

The site is promising for future dark matter and gravitational wave detection experiments.

Abstract

Atom interferometer (AI) experiments offer interesting prospects for searches for the interactions of ultralight bosonic dark matter with Standard Model particles as well as detection of gravitational waves in a frequency band inaccessible to experiments that are operating or under construction. Ideal locations for the next generation of such experiments are provided by long vertical shafts, such as that providing access to the Gotthard base railway tunnel from the Sedrun locality in the Canton Grisons of Switzerland. We present the results of an exploratory environmental measurement campaign at this location to evaluate the ground motion activity and the background electromagnetic field quality. We find that the backgrounds due to both ground motion and electromagnetic fields, including those due to passing trains, are low enough for successful operation of a 800-m AI experiment.