ET

Infrastructure and User Services    

The Einstein Telescope’s instrumentation is based on advanced metrology concepts: three pairs of two laser interferometers –one optimised for low- and one optimised for high frequencies– will be installed in an underground structure with a layout and with large cavern systems at each corner. The requirements for the technology are mindboggling and are best illustrated by the projected precision with which the mirror jitter due to the passage of a GW will be recorded: 0,000 000 000 000 000 000 01 m. ET’s first conceptual design was published in 2011 as the result of an EU-funded Design Study, and was then updated in 2020. It relies on the techniques pioneered and successfully implemented for GEO600, LIGO and Virgo: fabulous seismic isolation, large mirrors with low-noise dielectric coatings and silica fibre suspensions, high-power lasers and the use of squeezed light to reduce quantum noise to their physical limits. In addition ET’s design relies on two new and distinct innovative features. Firstly, ET will be sited at a low-seismic-noise underground-location for which three candidates have been identified: Sardinia in Italy, the Euregion Meuse-Rhine on the Belgian-Dutch-German border and Lusatia in Germany. Secondly, ET will rely on the use of crystalline silicon mirrors operated at cryogenic temperatures to suppress thermal noise and mirror distortions to a minimum.     

Examples/description of the type of research    

The Einstein Telescope (ET) will be Europe’s next-generation gravitational-wave (GW) observatory,  surpassing the achievable sensitivity of current GW observatories such as LIGO and Virgo by an order of magnitude. Whereas the LIGO-Virgo Collaboration opened a new window upon our Universe with the Nobel Prize winning direct detection of GWs from merging black holes, ET’s superior sensitivity is essential to fully exploit the potential of GWs. It will ‘hear’ mergers up to z=100, probing the era before first star formation. Each year, ET will detect about a million neutron-star and black-hole mergers, with masses extending up to several thousand solar masses. This   combination of large redshift coverage, wide black-hole mass range, high statistics and excellent accuracy sets the scene for enormous discovery potential in astrophysics, fundamental physics and cosmology. In addition to GWs from coalescing binaries, ET will be able to detect GWs from other sources such as supernovae and pulsars, and it might find a stochastic background from phase transitions in the very early Universe. ET will play a pivotal role in multi-messenger astronomy, combining GW information with that of radio, optical, IR, UV, X-ray, gamma-ray and neutrino telescopes as well as cosmic-ray observatories. ET’s low-frequency sensitivity allows to track GW signals for hours, so that Earth rotation will enable accurate sky localisation for early alerts to other observatories. And ET’s most exciting observations will be the surprises awaiting in our Universe to be unlocked by the combined power of GWs as a unique unstoppable messenger and ET’s unprecedented accuracy.    

How to access the infrastructure?    

The infrastructure will provide different levels of access, such as access to public data, access to privileged (embargoed) data, access to the facility for technology development. The most common access will be on the basis of becoming a member of the ET Collaboration. Membership allows to contribute to the design, development and building of the instrument, and making use of the data. Country membership to the infrastructure will be arranged through a yet to be established legal entity.