Experiments using charged-particle accelerators have led to remarkable discoveries about the nature of fundamental particles and the behavior of nuclear matter. These breakthroughs have been made possible by dramatic advances in our understanding of the physics and technology of particle acceleration. 1 Accelerator beam energies increased exponentially–by an order of magnitude every decade–for half a century after the pioneering days of John Cockcroft and Ernest Lawrence in the early 1930s, as established technologies were pushed to their limits and superseded by new ones (see figure 1).

The present state of the art for proton synchrotrons is the Large Hadron Collider (LHC), under construction at CERN on the French–Swiss border. Its 7-TeV proton beams will, in effect, provide experiments with constituent quark energies on the order of 1 TeV. Looking further ahead, particle physicists are already planning for an electron–positron collider with 250-GeV beams, a neutrino factory, and even...

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