Large Hadron Collider (LHC)

Image showing LHC experiments & pre-accelerators, 
by Arpad Horvath, via Creative Commons:
In the diagram above, the path of the protons (and ions) begins at linear accelerators (marked p and Pb, respectively). They continue through the booster (small unmarked circle), the Proton Synchrotron (PS), the Super Proton Synchrotron (SPS) and finally enter the LHC tunnel. 

In the LHC there are 4 large experiments (shown in yellow) with the following names:

ATLAS            A Toroidal LHC Apparatus
CMS                 Compact Muon Solenoid
LHCb               LHC-beauty
ALICE             A Large Ion Collider Experiment

The Large Hadron Collider (LHC) is the largest single machine and largest experimental facility ever built. Its 17 mile (27 km) circuit lies between 164 and 574 feet (50 and 175 metres) underground, with superconducting magnets (cooled to -271.25 deg C by liquid helium).  

The collider tunnel, 12 feet (3.8 m) in diameter, contains two parallel adjacent proton-carrying beam pipes (running in opposite directions with 4 sites of intersection).

Each proton travels 11000 times around it in 1 second. The protons are deliberately bunched together with over 100 billion protons per bunch - and with around 25 nanoseconds (ns) (or billionths of a second) between bunches. Usually, it is proton-proton collisions that are studied although collisions involving other types of particles (e.g. ions) are occasionally analysed.