by John Traveler

Created on: August 27, 2010

Up until the 1930’s, the miniature world of atoms and molecules was totally theoretical. In fact, to this day no one has ever beheld, in the visual sense, a single atom, only the electromagnetic effects of them . Then came the particle accelerator (originally called “atom smashers”), affording physicists glimpses into the nano-universe, just as the telescope has revealed the extents of the cosmic universe. Today, just about everything we know for sure about atomic structure is owed to particle accelerators.

There are three basic types of particle accelerators, the Van de Graaf electrostatic generator, Lawrence Livermore’s Cyclotron and linear accelerators. All three apparatuses use electromagnetic energy to accelerate the velocity, and thus energy level (E=mc2)  of electrons, positrons, protons and atomic nuclei, to near the speed of light. The relative energy of the accelerated particle is measured in electron volts (eV), or more often millions (MeV), Billions (GeV) or Trillions (TeV). Of course, it takes a lot of energy to do this, and the method of imparting energy to the particle in transit differentiates the three basic  types of accelerators.

The Van de Graaff type generator uses a very high static electrical charge to propel particles carrying either a negative or positive charge through a vacuum tube. The target at the other end of the tube is subjected to a high static charge of tens of MeV and of the opposite polarity to the particle being accelerated. Since charges of opposite polarity attract, the particle accelerates to high velocity and smashes into the target with very high energy. The cyclotron uses a circular vacuum tube and enormously powerful magnets to accelerate the particle.  Linear accelerators use high power radio frequency (RF) transmitters called “Klystrons” to produce a high frequency radio wave that is injected into a long vacuum tube. The particles to be accelerated, usually protons, are injected at one end of the tube and then essentially ride the radio waves down the tube. Since the radio waves propagate at very close to the speed of light the particles achieve the same velocity.  

The largest and most powerful accelerators today, Fermilab near Chicago and Cern in Switzerland, are cyclotrons several miles in diameter. But it was the 2-mile long Stanford Linear accelerator (SLAC) which came on line in 1966, and in 1968 breached new dimensions of practical quantum physics with

• 1
• 2
• Next Page >>