Carlos Santos, age 16, of E1 Paso, Texas, for his question:

WHAT IS A PARTICLE ACCELERATOR?

A particle accelerator is an electric device that speeds up the  movement of atomic particles. It can accelerate such particles as electrons or protons and give them extremely high amounts of energy.
Accelerators serve as valuable tools for scientific research into the nucleus of an atom. They enable physicists to change the atom of one element into that of another element. This change, called transmutation, results from reactions that happen when accelerated particles collide with the nucleus of any atom.
High energy accelerators also help physicists discover new kinds of particles and study their relation to the forces that hold the nucleus together.
Accelerators also have other important uses. In industry, electron accelerators are used as powerful X ray machines to detect hidden flaws in metal castings. In medicine, they serve as X ray machines and are used to diagnose and treat cancer.
Accelerators vary in design and size, but they all operate on the same general principles. They all use only electrically charged particles.
Most accelerators use electrons, which are negatively charged, or protons, which are positively charged. These particles are produced by devices outside an accelerator and then released into its vacuum chamber or tube.
Accelerators speed up particles by means of an electric field, a region of space in which an electric force acts on a charged body. Such a field is generally produced across a gap between a pair of electrodes to which an electric voltage has been applied. When particles pass through this accelerating gap, the electric field accelerates the particles by acting on their electric charges.
Physicists measure the energy of accelerated particles in units called electron volts.
Two physicists, Sir John Cockcroft of Great Britian and Ernest T.S. Walton of Ireland built the first accelerator in 1932. It produced protons of 400 electron volts.
Through the years, scientists in Europe and the United States have developed accelerators capable of higher and higher energies. In 1967, Soviet physicists built a 76 billion electron volt proton synchrotron in Serpukhov. In 1972, United States physicists accelerated protons to an energy of 400 billion electron volts. They used a giant synchrotron at the Fermi National Accelerator Laboratory in Batavia, I11.
Accelerators can be classified according to the kind of path followed by their accelerated particles. There are two basic types: circular and linear.
Circular accelerators use one or more large electromagnets to produce a strong magnetic field that makes particles travel in circular orbits.
Linear accelerators make atomic particles move in a straight line. In one kind of linear accelerator, the particles travel through a series of pipes called drift tubes that are separated by accelerating gaps.