CERN Proposes 100 Trillion Electron Volt Supercollider for 2040

The Future Circular Collider (FCC) collaboration submitted its Conceptual Design Report (CDR) for publication, a four-volume document that presents the different options for a large circular collider of the future. It showcases the great physics opportunities offered by machines of unprecedented energy and intensity and describes the technical challenges, cost and schedule for realization.

The FCC’s ultimate goal is to provide a 100-kilometer superconducting proton accelerator ring, with an energy of up to 100 TeV, meaning an order of magnitude more powerful than the LHC.

Using new-generation high-field superconducting magnets, the FCC proton collider would offer a wide range of new physics opportunities. Reaching energies of 100 TeV and beyond would allow precise studies of how a Higgs particle interacts with another Higgs particle, and thorough exploration of the role of the electroweak-symmetry breaking in the history of our universe. It would also allow us to access unprecedented energy scales, looking for new massive particles, with multiple opportunities for great discoveries. In addition, it would also collide heavy ions, sustaining a rich heavy-ion physics programme to study the state of matter in the early universe.

“Proton colliders have been the tool-of-choice for generations to venture new physics at the smallest scale. A large proton collider would present a leap forward in this exploration and decisively extend the physics programme beyond results provided by the LHC and a possible electron-positron collider.” said CERN Director for Research and Computing, Eckhard Elsen.

A 90-to-365-GeV electron-positron machine with high luminosity could be a first step. Such a collider would be a very powerful “Higgs factory”, making it possible to detect new, rare processes and measure the known particles with precisions never achieved before. These precise measurements would provide great sensitivity to possible tiny deviations from the Standard Model expectations, which would be a sign of new physics.

The cost of a large circular electron-positron collider would be in the 9-billion-euro range, including 5 billion euros for the civil engineering work for a 100-kilometer tunnel. This collider would serve the worldwide physics community for 15 to 20 years. The physics programme could start by 2040 at the end of the High-Luminosity LHC. The cost estimate for a superconducting proton machine that would afterwards use the same tunnel is around 15 billion euros. This machine could start operation in the late 2050s.

Enhancing the Large Hadron Collider to 27 TeV

The project would also include boosting the existing LHC with new more powerful superconducting magnets. The HE-LHC project features a pp collider, which extends the current energy frontier by almost a factor 2 (27 TeV collision energy) and an integrated luminosity of at least a factor of 3 larger than the HL-LHC.

FCC Hadron Collider

Recognizing that circular proton-proton colliders are the main, and possibly only, experimental tool available in the coming decades for directly exploring particle physics in the energy range of tens of TeV, the FCC study prepares for a 100 TeV hadron collider (FCC-hh) as the next step. FCC-hh will increase the mass reach by almost an order of magnitude and the integrated luminosity by a factor of 50 with respect to the LHC thus being able to access a large range of new physics opportunities.

Together with a heavy ion operation programme and the possibility of integrating a lepton-hadron interaction point (FCC-he), it provides the amplest perspectives for research at the energy frontier.

The total length of the arcs is 83.75 km. The lattice in the arc consists of 90° FODO cells with a length
of about 213 m and six 14 m-long dipoles between quadrupoles. The the dipole filling factor is about 0.8,
hence a dipole field just below 16 T is required to keep the nominal beams on the circular orbit.
The dipoles use Nb3Sn conductors at a temperature of 2 K to reach this field and are a key cost
item. A focused R&D programme to increase the maximum current density in the conductors to at least
1500 A/mm2 at 4.2 K temperature started in 2014 (currently 1200 A/mm2 has been achieved). Based on this performance, several optimized dipole designs have been developed in the EuroCirCol H2020 EC funded project – each implementing a different design concept. This allowed the amount of conductor material to be minimized and led to the choice of the cosine-theta design as the baseline. Collaboration agreements are in place with the French CEA, the Italian INFN, the Spanish CIEMAT, the Swiss PSI and the Russian BINP organizations, to build short model magnets based on the designs. In addition, a US DOE Magnet Development Programme is working to demonstrate a 15 T superconducting accelerator magnet.

If the FCC-hh is implemented following a lepton collider (FCC-ee) in the same underground infrastructure, the time scale for design and R&D for FCC-hh is lengthened by 15 to 20 years. Additional time will be used to develop alternative technologies, e.g. magnets based on high-temperature superconductors, with potentially a significant impact on the collider parameters (e.g. increase of beam energy), relaxed infrastructure requirements (cryogenics system) and increased energy efficiency (temperature of magnets and beamscreen).

Over the next two years, the particle physics community will be updating the European Strategy for Particle Physics, outlining the future of the discipline beyond the horizon of the Large Hadron Collider (LHC). The roadmap for the future should, in particular, lead to crucial choices for research and development in the coming years, ultimately with a view to building the particle accelerator that will succeed the LHC and will be able to significantly expand our knowledge of matter and the universe. The new CDR contributes to the European Strategy. The possibility of a future circular collider will be examined during the strategy process, together with the other post-LHC collider option at CERN, the CLIC linear collider.