The Long-Term Future of Particle Accelerators

This talk is going to deal with the big machines that are used to do research on the smallest parts of matter and on the way they interact. In fact, at the bottom of all physical phenomena are particles and forces between particles. To observe these on an even smaller scale, we have to accelerate the particles to high energy. The reason is very fundamental: it is Heisenberg's uncertainty principle that is at the basis of all modern physics. The uncertainty in position, multiplied by the uncertainty is momentum, cannot be smaller than Planck's constant h. So, if we want precise position measurements to study small things, the momentum of the particles involved should not be too low, because this would imply a precise knowledge of momentum so that Heisenberg's principle would be violated.

Another way of saying the same thing is that each particle can also be interpreted as a wave; for looking at small details we need a short wavelength and this again corresponds to high momentum.

The only way that we know to accelerate particles to high energy is to use charged particles and to let them move in an electric field. If, for instance, an electron moves from a negative electrode to a positive one, it gains energy equal to the potential difference (volts) multiplied by the particle's charge. The energy is expressed in electron volts (eV); this is the amount gained by an electron moving across a potential difference of one volt.