Ironically, synchrotron radiation, although now greatly in demand, was a bane in the life of high-energy physicists working with particle accelerators. This is because the radiation represents a loss of energy.

Credit: TESLA

In particle accelerators, charged particles travel millions of times round a doughnut-shaped ring containing a vacuum. Strategically placed magnets confine the particles to their circular path. The strength of the magnetic field must change as the particles accelerate, in order to keep them on course. Because this change must be synchronized with the energy gain associated with increasing the particles' speed, the radiation emitted acquired the name synchrotron radiation.

Particle accelerators are designed to compensate for the energy loss, but once scientists saw that synchrotron radiation might be useful, machines were built specifically to produce it — the 'second-generation' facilities. In these systems, the particle beams are confined in a 'storage ring' and siphoned off in a controlled manner along a beamline.

Instruments in the beamlines, such as monochromators, determine the frequencies available for a particular class of experiments — perhaps probing for fault lines or impurities in a material, or X-ray diffraction to determine a protein structure.

As accelerator physicists learned more about synchrotron radiation, they designed magnets engineered with precise proportions to increase the energy and brightness in a beam and so expand its potential range of applications. Instead of squeezing these 'insertion devices' into synchrotrons as an afterthought, 'third-generation' synchrotrons are specially designed with the devices in mind. One such facility, the Swiss Light Source, is scheduled to come online this August in Villigen, and Diamond and Soleil are planned for later this decade in Britain and France.