To go much beyond the FCC entirely new concepts will be
needed.
One promising path is circular crystal colliders (CCCs), where
bent crystals, with an effective field of several 100 or 1000 T, take
on the role of dipole or quadrupole magnets in present-day accelerators,
as is sketched in Fig. 8. Unlike conventional storage rings
where particles are accelerated by raising the dipole magnetic
field, in CCCs the bent crystals, defining the ring geometry, are static
and the stored charged particles are accelerated instead by
induction RF units [43,44]. Fig. 9 presents a possible evolution of
the circular CERN/FCC complex with a 1000-TeV CCC as its final
stage.