A dual tunnel structure for the Einstein Telescope

TL;DR

This paper proposes a new dual tunnel architecture for the Einstein Telescope that significantly reduces excavation volume and enhances seismic isolation, stability, and geophysical monitoring capabilities for gravitational wave detection.

Contribution

It introduces a novel dual tunnel design with integrated seismic isolation systems and real-time rock motion monitoring, improving performance and maintenance over traditional approaches.

Findings

Reduces excavation volume by an order of magnitude.

Enhances seismic isolation and stability of the interferometers.

Provides real-time rock motion monitoring for improved noise cancellation.

Abstract

We present a novel tunnel architecture for the Einstein Telescope that departs from the traditional large-cavern approach and reduces the excavated volume by an order of magnitude. In the proposed design, all seismic isolation systems are housed in raise-bore wells drilled upward from the main tunnel toward an upper service tunnel. The pre-isolators for the most sensitive optics are located in the service tunnel, seating directly on strong and compact rock, while the other filters are distributed along the wells within compact, side-access vacuum chambers. Shorter, separate wells accommodate the seismic isolation systems for less demanding optics. This configuration provides substantial advantages: easier lock acquisition and improved robustness of the interferometers, lower-frequency pendulum stages, reduced congestion around the test masses, simplified installation and maintenance, improved vacuum partitioning, strong physical decoupling between the high- and low-frequency interferometers, and enhanced compatibility with future advances of Newtonian-noise cancellation. A novel technique for real-time, precision monitoring of rock motion and tilt provides a new signal for Newtonian noise cancellation and enables correction of seismic disturbances even during earthquakes, offering unique geophysical measurement capabilities.