R&D and Interdisciplinarity
Gravitational waves travel through space-time, deforming it and producing mini “space-time quakes”. In this slightly warped space-time, material bodies are strained, and distances are stretched and squeezed alternatively. That’s a very tiny effect though: when a gravitational wave crosses Virgo, the 3-km arms of the detector are stretched by only a billionth of a billionth of a meter, i.e. less than a thousandth of the diameter of a proton.
The gravitational waves are detected by the 3 L-shaped interferometers (Virgo and the 2 LIGO’s) whose arms are in a vacuum; through which laser beams propagate, reflected by mirrors placed at the two opposite edges, isolated from seismic vibrations and from the atmospheric environment by inverted pendulums.
With these instruments, scientists are aiming at the extremely difficult art of capturing a gravitational wave signal of cosmic origin by distinguishing it from the slightest possible deviation caused by terrestrial seismic movements, atmospheric pressure variations, cloud passage, sea waves, acoustic and electromagnetic noise, anthropogenic movements, as trucks, trains, windmills, helicopters.
In order to do so the Virgo collaboration and the EGO personnel have to develop state of the art technology on many fronts (click the scheme below to learn more).
extreme quality mirrors (Reflection> 99.999%, optical absorption < 1ppm, flatness < 0.5 nm, scattering < 10 ppm)
a sophisticated distributed network of sensors to evaluate and subtract environmental background: electromagnetic perturbations, non-stationary ground deformations, sea waves, cloud passage, electromagnetic waves, cosmic rays, acoustic noise vibrations, anthropogenic movements
a sophisticated distributed and intelligent system of feedback controls and state of the art data analytics, machine and deep learning methods
state of the art laser injection system as well as a state-of-the-art detection and protection system, including sensors and baffles to control stray light, producing noise and, in the squeezed quantum state regime, de-coherence
super-attenuators damping seismic vibrations (<10-12 seismic reduction) of all the sensitive parts of the interferometer
ultra-high vacuum in the two 3 km tubes (P<10-9 Torr, the highest volume vacuum in Europe for Virgo and second in the world after the LIGO antenna’s having 4km tubes)
advanced quantum sensing techniques (frequency squeezing) taking the measurement errors below the quantum limit
The developments of Interferometers thecnology have improuved our senstivity to both low frequencies (from 1 to 10 Hz) as higher frequencies (around kHz) and this could trigger important innovations, for instance to earth-science (seismology, climate change) and distributed smart networks of sensors (Industry 4.0) as well as to the technology of quantum sensors.
The above make EGO, an interdisciplinary and technological hub, open to interdisciplinary collaboration, with Geoscientists (e.g. the Instituto Nazionale di Geofisica e Vulcanologia – INGV, the Institut de la Physique du Globe de Paris – IPGP, and other Geoscientific organizations in Europe), Atmospheric Scientists and Ecology scientists with the University of Pisa , Measure and Electromagnetic Compatibility experts at the University of Pisa and data science experts, from low latency distribution of alerts, to state of the art data analytics and machine and deep learning techniques of data analysis.
We thus have the ASPIS project which is INGV-EGO co-project for fast (few sec) warning, for which we won the contest with Regione Toscana financing one scholarship. We also have a collaboration with the network of Electromagnetic sensors of Renato Romero, the online data streaming is active (see http://www.vlf.it/virgo/virgo.html) and is bing very useful to learn about low noise EM pollution at EGO site, the aim is to have clean monitoring of EM Earth global noise.
We also have a (crucial for GW science) agreement with Provincia di Pisa, since 2006, in order to preserve “the noise climate around the site”. In the past years we had several notifications and requests of evaluation of potentially noisy plants within a 5 km radius from us, as wind turbine farms, earth quarries, waste processing, solar panels, shooting plants… and we have worked out mutually working solutions. We finally have an agreement with the Brigade 46, which issued a note for the establishment of a “no-fly zone” around the sensitive parts of the interferometer.