The first particle accelerators built were linear accelerators 6(linacs). These machines were constructed on the notion of producing particles in one part of a machine and then using a strong electric field to accelerate them to high energies across the machine. At the opposite end of the machine, the particles were caused to collide with a target. Linacs possess one inherent disadvantage, however. To increase the energy of particles, the machine must be made longer and longer. For example, in order to build the two mile (3.2 km) linac at Stanford University in an exactly straight line, the engineers who designed it had to make sure it did not follow the Earth's curvature. Scientists were aware of this problem early on and looked for ways to deal with it. The most successful solution was that proposed by E. O. Lawrence in the early 1930s. Lawrence suggested that particles be...