Plasma physics: surfing the wake

For almost 60 years, physicists have used strong, large-scale electric fields to accelerate charged subatomic particles. Unfortunately, these conventional particle accelerators, RF linacs, have reached a limit: at an electric field strength of about 107 V m-1, the support structures break down — sparks fly, short-circuiting the accelerator. So, in order to reach higher particle energies one is forced to build ever larger linear accelerators, or bend the particles into a circular path using magnets (which produces another problem, as the particles then radiate away much of their energy). In theory, this electric-field problem can be overcome by plasma particle accelerators, because plasma, as an ionized medium, has already broken down and is therefore not susceptible to electron dissociation. Plasma waves can generate accelerating electric fields thousands of times greater than the most powerful conventional accelerators. And in Physical Review Letters , Amiranoff and colleagues now report1 an experiment that brings the 'table-top' plasma accelerator a step closer to reality.