How Particle Accelerators Work

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 the discovery that protons were composed of smaller particles called quarks. Since then, many other exotic particles such as anti-protons, anti-leptons, mesons, bosons and so on have been discovered and studied in particle accelerators.

When accelerated particles impact a target, the relative release of energy literally blows the particles and target material to bits. Detectors are used to detect different types of matter and energy residue liberated by the collision. In addition, many accelerators have side rings that are essentially mini accelerator vacuum tubes, where specific particle debris can be captured for further study and even secondary collisions and other experiments.         

By using particle accelerators, mans understanding of quantum states and how subatomic particles interact is almost complete. It is hoped that  Cern’s new Hadron Collider, syncro-cyclotron, which uses super-cooled conductor magnets, is expected to provide the next major development and perhaps the final pieces of the quantum puzzle, the relationship between energy and matter, the final clues to an understanding of how the universe came to be at the very moment of the big bang. What is unique about the Hadron Collider is that it uses two parallel tubes to accelerate particles in opposite directions. Once the particles are up to speed, they are diverted slightly from their trajectories to cause a head on collision. Since both particles are traveling at near the speed of light the relative velocity is almost twice the speed of light and therefore of a much higher energy level than any collision achieved to date.

The Cern syncro-cyclotron is not fully operational yet, but when it is, the particle physics community is optimistic of new and profound discoveries. Many questions may find answers and theories like string theory may be proven or disproved. The notion of  parallel dimensions of the universe may be realize or relegated to obscurity.  Physicist may even be able to create a miniature black hole in an accelerator, but there is growing concern about even attempting such a feat.  Who knows what other insights and possibilities particle accelerators will offer mankind in his quest to unlock the secrets of matter and energy, and thereby the universe we find ourselves in.