CERN Accelerating science

This website is no longer maintained. Its content may be obsolete. Please visit for current CERN information.

Home | Sitemap | Contact us
this site all CERN
The HMPID detector before final installation inside the ALICE magnet


Particles for all purposes

Physicists at CERN explore many different aspects of the microworld, from deep inside the atomic nucleus to the mysteries of antimatter. They perform a wide range of experiments, which use beams of energetic particles produced in the accelerator complex. Each experiment involves specialised equipment – the detectors – to record what happens when the beam hits either a ‘fixed’ target or particles in a similar beam coming from the opposite direction.

At the lowest energies, the Proton-Synchrotron Booster supplies beam to ISOLDE, a unique source of radioactive isotopes for experiments with applications that range from astrophysics to industry and medicine.

The Proton Synchrotron (PS) delivers higher energy protons to two contrasting experiments. DIRAC is testing ideas about the strong fundamental force, while CLOUD is finding out how natural high-energy particles might influence the formation of clouds. The PS also provides the protons that create the antiprotons for the Antiproton Decelerator (AD), where physicists are learning more about antimatter in the ALPHA, ASACUSA and ATRAP experiments. The ACE experiment also uses antiprotons, in this case to assess their suitability for cancer therapy.

The next largest accelerator is the Super Proton Synchrotron (SPS), where COMPASS focuses on investigating hadrons - particles made of quarks, including the nucleons (protons and neutrons) of ordinary matter.

The Large Hadron Collider (LHC), CERN’s most powerful accelerator, hosts six experiments designed to find out how the particles of matter behave at a new high energy frontier. The experiments are located at points where the LHC’s two beams, which travel in opposite directions, collide head on.

There is also one experiment that uses none of the beams from CERN. CAST looks at the Sun for hypothesised particles called ‘axions’.