Chapter3 2 3. From the Eloisatron to the Pevatron

Abstract In the late 1970s the experimental physics community was active in promoting the Large Electron Positron (LEP) collider and its associated experiments to study the Z- and W-bosons, and with the expectation that the tunnel could subsequently house a hadron collider (LHC), providing a center-of-mass energy for discoveries at the frontier of knowledge. At this time, Antonino Zichichi, who had chaired a Working Group in charge of promoting LEP among the community of experimental and accelerator physicists, realized that one should envisage building as large a ring as possible, for which LEP/LHC would be but a scale model, and it was thus the idea of the Eloisatron, or ELN, in a ring of about 300 km in circumference, was born. CERN and IHEP, China, are now engaged in studies for future colliders of 100 km in circumference, aiming to extend center-of-mass energy in hadron collisions to 100 TeV by using very high field magnets. The ELN idea lives on, but it is time to envision an update. A ring of diameter 300 km would make possible the installation of a sequence of increasingly complex accelerators culminating in one eventually capable of providing a center-of-mass energy of 1000 TeV, i.e. a peta-electron-volt or PeV.