The European Organization for Nuclear Research (CERN) has signed a third memorandum of understanding to broaden its partnership with the Einstein Telescope (ET) project, aiming to leverage synergies between particle accelerator technology and next-generation gravitational-wave detection. As CERN continues work on future collider concepts such as the Future Circular Collider (FCC), the agreement extends cooperation into engineering and safety studies—key elements in both underground gravitational-wave facilities and large-scale accelerator complexes.
Gravitational Waves and Particle Colliders: Complementary Windows on the Cosmos
A Century-Old Prediction Realized
In September 2015, the Laser Interferometer Gravitational-Wave Observatory (LIGO) and Virgo collaborations recorded the first direct detection of gravitational waves—minute ripples in space-time predicted by Albert Einstein’s general theory of relativity in 1916. Generated by cataclysmic astrophysical events such as black-hole or neutron-star mergers, these signals opened an entirely new observational channel for astronomy.
Microscopic Versus Macroscopic Probes
Where gravitational-wave observatories study the Universe at its largest scales—mapping cosmic collisions and probing the very fabric of space—particle accelerators like CERN’s Large Hadron Collider (LHC) recreate the high-energy conditions moments after the Big Bang. By smashing fundamental particles together at near-light speeds, accelerators allow physicists to investigate the building blocks of matter and the forces governing them. The ET, if constructed, will serve as Europe’s most sensitive gravitational-wave detector, while CERN pursues high-energy colliders to explore beyond the Standard Model of particle physics.
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The Einstein Telescope: A Next-Generation Observatory
Design and Sensitivity Improvements
The Einstein Telescope represents the third generation of ground-based gravitational-wave detectors. Unlike its surface-level predecessors, LIGO in the United States and Virgo in Italy, the ET will be situated hundreds of meters underground to reduce seismic noise and ambient disturbances. Its distinctive triangular layout—with three arms, each 10 kilometers long—will house ultra-stable lasers and vacuum systems to measure length changes thousands of times smaller than a proton’s diameter. By extending sensitivity down to a few hertz, the ET will detect sources much earlier in the inspiral phase, dramatically improving sky localization and event rates.
Scientific Goals and Timeline
The ET’s goals encompass a broad science case: tracking the formation and evolution of black holes across cosmic history, elucidating the equation of state of neutron stars, testing gravity in its strongest regimes and probing the Universe’s infancy within seconds of the Big Bang. The project is now in its feasibility and site-selection phase, with construction aimed to commence in the early 2030s. If all proceeds according to plan, the facility could begin collecting physics data by 2040.
CERN’s Multi-Year Collaboration with ET Partners
First Collaboration: Vacuum, Materials and Surface Treatments (October 2022)
Recognised as an official CERN experiment in mid-2022, the ET consortium began formal cooperation with CERN when Nikhef (the Dutch National Institute for Subatomic Physics) and Italy’s INFN (Istituto Nazionale di Fisica Nucleare) signed an agreement covering key technological areas. CERN’s decades of expertise in ultra-high vacuum systems—vital for both LHC beam pipes and the ET’s laser arms—alongside materials science, precision manufacturing and advanced surface treatments, made it an ideal partner. Under this first accord, CERN engineers and scientists advised on vacuum-pumping strategies, vacuum-chamber welding techniques and the development of low-outgassing materials.
Second Collaboration: Civil Engineering Expertise (September 2023)
As the ET design matured, the site-characterisation and civil-engineering phases kicked off. In September 2023, CERN formalised its contribution by signing an agreement to share know-how in large-scale underground excavation, tunnel lining and structural geomechanics. Drawing on CERN’s experience with the 27-kilometre LHC tunnel and its network of service galleries, the collaboration addressed challenges such as rock stability, water ingress mitigation and seismic isolation—critical to ensuring the ET’s arms remain stable over decades.
Third Collaboration: Engineering and Safety Systems (March 2025)
The most recent memorandum, signed in March 2025, extends cooperation into the realms of power distribution, signal cabling, cooling and ventilation, access control and occupational health and safety. Narrowing the gap between accelerator and detector infrastructures, CERN’s Engineering department will support the ET in areas including:
• Power-grid interface design and redundancy planning, drawing on LHC power management strategies.
• High-capacity signal-cable routing and optical-fiber installation, utilising CERN’s experience with particle-detector data networks.
• Precision cooling and ventilation systems to maintain temperature and humidity stability in underground caverns.
• Configuration management and project-coordination methodologies adapted from CERN’s accelerator upgrade projects.
• Integrated safety analysis, leveraging CERN’s Health, Safety and Environment (HSE) unit in crafting emergency-response procedures, fire-suppression system design and personnel-access protocols.
“Combining technical-infrastructure design and safety considerations within a single framework is an efficient model,” explains Jean-Philippe Tock of CERN’s Engineering department. “This collaboration aligns perfectly with CERN’s expertise and our ongoing work on future colliders such as the FCC, where underground infrastructure and large-scale safety systems are core challenges.”
Safety Innovations for a Groundbreaking Facility
Beyond simply adopting existing safety models, the ET demands novel solutions. “When you build a facility like this underground, you face unique hazards—confined-space rescues, tunnelling risks and complex evacuation dynamics,” notes Saverio La Mendola of CERN’s HSE unit. Drawing on experience from CERN’s deep-underground halls (e.g., CERN’s LHC access galleries), the collaboration will develop innovative safety systems, including real-time environmental monitoring, multi-layered access control and AI-augmented evacuation simulations.
Implications for the Future Circular Collider and Beyond
Synergies with FCC Infrastructure
CERN’s flagship future project—the Future Circular Collider—envisions a 100-kilometre tunnel hosting next-generation hadron and electron–positron colliders. The ET collaboration provides a testing ground for tunnel-engineering techniques, large-volume safety-system designs and integrated project management approaches that will scale to the FCC’s ambitious scope. “Knowledge exchange with the ET consortium accelerates our readiness for the FCC,” says Tock. “Lessons learned in geology, infrastructure integration and safety can be directly applied to our own strategic road map.”
Broader Impact on European Science Infrastructure
By partnering with the ET in a tri-national effort involving the Netherlands, Italy and CERN, Europe strengthens its position at the forefront of multi-messenger astronomy and particle physics. European science ministers and the European Strategy for Particle Physics are closely watching both projects, recognising that gravitational-wave astronomy and high-energy colliders form a complementary toolkit for fundamental discovery.
Next Steps: Site Selection, Technical Design Report and Funding
Decision on Location
During the current study phase, potential sites in Sardinia (Italy), Euregio Meuse-Rhine (Belgium–Germany–Netherlands) and other European regions are under evaluation. Criteria include seismic quietness, geological stability, existing infrastructure and regional support. Host-country commitments on funding, environmental permits and local partnerships will weigh heavily in the final decision, anticipated in 2026.
Preliminary Technical Design Report (pTDR)
With the extended collaboration agreement in place, CERN and ET partners will jointly produce a pTDR by late 2027. This blueprint will incorporate integrated engineering designs, civil-works plans, safety analyses and cost estimates, forming the basis for funding proposals to the European Commission, national research agencies and potential industry partners.
Operational Targets
Subject to timely site confirmation and funding, construction could begin by 2030. The detector’s underground caverns and laser arms are slated for completion by 2035, with commissioning and calibration through 2040. Full-scale scientific operations are targeted to start that year, ushering in a new era of gravitational-wave astronomy.
Conclusion: A Shared Vision for Fundamental Science
The expanded CERN–Einstein Telescope collaboration exemplifies Europe’s commitment to synergistic science infrastructure—melding the microscopic explorations of particle physics with the cosmic reach of gravitational-wave detectors. By pooling expertise in vacuum technology, civil engineering, systems integration and safety, CERN and ET partners aim to unlock discoveries on both the smallest and largest scales. As Jean-Philippe Tock observes, “We stand at the threshold of a golden age, where fundamental particles and fundamental spacetime ripples are studied side by side. Together, these ventures will illuminate the Universe from the infinitesimal to the infinite.”
With its strategic alliances and shared engineering prowess, Europe is setting the stage for transformative insights into the nature of matter, energy and space-time—pursuits that will inspire generations of scientists and deepen humanity’s cosmic perspective.
