The core of the Future Circular Collider (FCC) project is a hadron collider called "FCC-hh" which aims at colliding proton beams with a centre of mass energy of 100 TeV - more than seven times the energy that can be reached in the LHC.

A team of experts from a large number of collaborating institutes and led by Daniel Schulte from CERN is designing FCC-hh and has reached the first important milestone at the end of September: a baseline for the machine layout and the main parameters of this collider. This will now form the basis for a more detailed design and in particular for a conceptual design report that is foreseen in 2018.

The dimensions of this collider are impressive; it would be hosted in a 100 km tunnel and consists of eight straight sections connected by arcs, as illustrated in Figure 1. It is currently planned that two of these sections accommodate high-luminosity experiments, two others could house additional, lower-luminosity experiments, whilst the other insertions would be used to inject fresh beams, clean the beams during operation, and extract the used beams.

The collider parameters have been chosen to fulfil the requests from the theoretical and experimental physics community. The collider layout permits using the LHC as an injector, and is compatible with CERN’s existing accelerator chain, though other options will also be explored. 

The collider layout sets demanding goals for the designers of each subsystem. To meet these goals the R&D in the coming years will push a variety of technology frontiers to come to a feasible technical design. This includes for example very high field magnets, a powerful cryogenic vacuum system and a beyond state-of-the-art beam collimation system.

To achieve the envisioned high beam energies the magnets in the storage ring arcs need to reach twice the field strength of the magnets used in the LHC. This requires the use of novel superconducting materials and magnet designs. The synchrotron radiation emitted by the beams when forced on their circular orbit will be 100 to 1,000 times larger than in the LHC. This will require a new approach to the design of the beam pipes and associated cooling systems. Finally, the energy stored in the two beams will be about 16 GJ. The collimation system will need to clean these beams and protect the machine from an accidental beam loss.

In addition, in the FCC-hh scenario, the rate of proton-proton collisions is very high to provide a large number of interesting events to the detectors. The debris of these collisions has a power of 500 kW. An efficient shielding is being designed to protect the detector and machine components. Two sets of machine parameters that have now been determined are summarized in Table 1.

The column “Baseline” describes the initial performance whilst the column “Ultimate” represents the performance that could be expected after several years of operation.

The collaboration will now design and optimise the different systems of the collider to present a conceptual design in 2018 that reaches the target performances.

The articel originally appeared in November's issue of Accelerating News.