An atom smasher is a large installation commonly referred to as a particle accelerator. It works by accelerating electrons to a significant fraction of the speed of light and then crashing them into the nuclei of atoms. The resulting debris can then be searched for otherwise elusive particles that can shed light on theories of physics.
As of 2014, the largest particle accelerator in the world is the Large Hadron Collider in Bern, Switzerland. The LHC went active in 2008, as part of the CERN accelerator complex, and consists of a 27-kilometer ring of supercooled magnets that act as superconductors. The bulk of the LHC apparatus is an elaborate cooling system that maintains these magnets an operating temperature of -271.3 degrees Celsius. This temperature, which is colder than the average temperature of outer space, is necessary to allow the free flow of current through the magnets and dramatically boost their power.
Inside the accelerator track, a powerful magnetic field contains the electrons that are to be accelerated. This keeps them away from the inner walls of the track and allows them to flow downrange unobstructed. Accelerators along the track give the electrons a speed boost along the way. At the end of the track, the electrons smash into atoms that have been injected into the system. The force of the impact releases subatomic particles that have been predicted by theory. Detecting the particles in the accelerator's chamber helps to verify current models of theoretical physics.