Particle Accelerators—atom Smashers

Particle accelerators, which can be thought of as giant microscopes able to peer deep into the atom, use electrical forces to boost protons or other charged particles to very high speeds. The faster the particles go, the more energy they possess. The earliest particle accelerators could fit on a tabletop, but they grew progressively larger as physicists sought to achieve higher and higher energies. Fermilab, the world's most powerful accelerator, which began operation in 1972, has an accelerating ring 6.4 kilometers (4 miles) around. And the Superconducting Super Collider (SSC), a huge accelerator that was being constructed in Texas until the United States Congress ended its funding in late 1993, would have been 87 kilometers (54 miles) in circumference.

The energy imparted to a speeding particle in an accelerator is expressed in units called electronvolts. An electronvolt (eV) is a tiny energy unit, the energy gained by a single electron passing through a 1-volt battery. (A standard flashlight battery is 1.5 volts.) But particles can be accelerated to enormous energies. The first generation of particle accelerators, developed in the early 1930's, accelerated beams of particles to energies of about 1 million electronvolts (MeV), and by the early 1950's machines had been developed that produced energies in the billions of electronvolts (GeV, from giga, the prefix for billion).

The early particle accelerators were often called “atom smashers,” because they were used to break atomic nuclei apart for study. Over a period of 25 years, these machines unlocked most of the secrets of the nucleus. And with larger machines in the GeV range, physicists discovered that the proton and neutron were not simple objects but had complicated internal structures.