III.3 — Introduction to CERN and its accelerator complex

The CERN accelerator complex has evolved over nearly 70 years, from the first 16 m circumference machine in 1957, the Synchrocyclotron, to the most powerful synchrotron in the world to today, the LHC, with 27 km circumference. In between, a series of machines were designed, installed and commissioned and most of them are still in operation serving, with an impressive zoo of particles, the very rich and diverse physics programmes carried out at CERN. This chapter gives an overview of the proton and ion accelerator complex, as well as a summary of the different fixed-target experimental areas and facilities served by the complex.