The Synchrocyclotron (SC) in building 300
The red magnet of CERN's first accelerator, the Synchrocyclotron (SC), has occupied a large part of Hall 300 since it was installed in the late 1950s. The remaining part of the 300-square-metre building has been used as a storage room since the accelerator was shut down in 1990. Now a public exhibition will breathe new life into the hall. (Image: CERN)

The 600-MeV Synchrocyclotron (SC), which came into operation in 1957, was CERN’s first accelerator. It provided beams for CERN’s first experiments in particle and nuclear physics.

At that time, theory predicted that a short-lived particle called the “pion” should decay into an electron and a neutrino, so scientists designed an SC experiment to stop pions and study their decays. In 1958, only a few hours after the start of the experiment, the first images showed clear evidence of this rare decay. This discovery spread CERN’s name around the world.  

Over the following years, scientists at the SC continued to make many important measurements on particles, atoms and nuclei. In 1964, this machine started to concentrate on nuclear physics alone, leaving particle physics to the newer and more powerful Proton Synchrotron.

In 1967, it began supplying beams for a dedicated radioactive-ion-beam facility called ISOLDE, which still carries out research ranging from pure nuclear physics to astrophysics and medical physics. In 1990, ISOLDE was transferred to the Proton Synchrotron Booster, and the SC closed down after 33 years of service.

A project to turn the SC into a visitor exhibition was carried out in time for CERN’s 2013 open days, and the SC exhibition is now one of the visit itineraries for CERN guided tours.