Tunnel Configurations and Seismic Isolation Optimization in Underground Gravitational Wave Detectors

Applied Sciences, vol. 12, pp. 8827

Abstract

The Einstein Telescope will be a gravitational wave observatory comprising six nested detectors, three optimized to collect low-frequency signals, and three for high frequency. It will be built a few hundred meters under Earth’s surface to reduce direct seismic and Newtonian noise. A critical issue with the Einstein Telescope design are the three corner stations, each hosting at least one sensitive component of all six detectors in the same hall. Maintenance, commissioning, and upgrade activities on a detector will cause interruptions of the operation of the other five, in some cases for years, thus greatly reducing the Einstein Telescope observational duty cycle. This paper proposes a new topology that moves the recombination and input–output optics of the Michelson interferometers, the top stages of the seismic attenuation chains and noise-inducing equipment in separate excavations far from the tunnels where the test masses reside. This separation takes advantage of the shielding properties of the rock mass to allow continuing detection with most detectors even during maintenance and upgrade of others. This configuration drastically improves the observatory’s event detection efficiency. In addition, distributing the seismic attenuation chain components over multiple tunnel levels allows the use of effectively arbitrarily long seismic attenuation chains that relegate the seismic noise at frequencies farther from the present low-frequency noise budget, thus keeping the door open for future upgrades. Mechanical crowding around the test masses is eliminated allowing the use of smaller vacuum tanks and reduced cross section of excavations, which require less support measures.

Authors 8

1. Florian Amann Aachen Engineering Geology

   Fraunhofer Research Institution for Energy Infrastructures and Geotechnologies IEG · RWTH Aachen University

   Affiliation as printed

   Engineering Geology, RWTH Aachen, Lochnerstrasse 4-20, D-52064 Aachen, Germany

   Fraunhofer Research Institution for Energy Infrastructure and Geothermal Systems IEG, Competence Center Geomechanics and Georisks, D-52064 Aachen, Germany

2. F. Badaracco corresponding

   UCLouvain

   Affiliation as printed

   Centre for Cosmology, Particle Physics and Phenomenology, Université Catholique de Louvain, B-1348 Louvain-La-Neuve, Belgium

3. R. DeSalvo

   University of Sannio · University of Utah

   Affiliation as printed

   Department of Physics & Astronomy, University of Utah, 115 South 1400 East 0830, Salt-Lake-City, UT 84112, USA

   Dipartimento di Ingegneria, Università del Sannio, C.so Garibaldi 107, 82100 Benevento, Italy

   Riclab LLC, 1650 Casa Grande Street, Pasadena, CA 91104, USA

4. Luca Naticchioni

   Istituto Nazionale di Fisica Nucleare, Sezione di Roma I

   Affiliation as printed

   INFN-Sezione di Roma, 00185 Roma, Italy

5. Andrea Paoli

   European Gravitational Observatory

   Affiliation as printed

   EGO, European Gravitational Observatory, Via Edoardo Amaldi, 556021 Cascina, Italy

6. L Paoli

   European Gravitational Observatory

   Affiliation as printed

   EGO, European Gravitational Observatory, Via Edoardo Amaldi, 556021 Cascina, Italy

7. Paolo Ruggi

   European Gravitational Observatory

   Affiliation as printed

   EGO, European Gravitational Observatory, Via Edoardo Amaldi, 556021 Cascina, Italy

8. Stefano Selleri

   Istituto Nazionale di Fisica Nucleare, Sezione di Firenze · University of Florence

   Affiliation as printed

   Department of Information Engineering, University of Florence, Via di S. Marta, 3, 50139 Firenze, Italy

   INFN Sezione di Firenze-Urbino, Via G. Sansone, 1, 50019 Sesto Fiorentino, Italy