Brilliance of X-rays

How is synchrotron light produced?

When a charged particle travelling close to the speed of light is accelerated, it emits the broad spectrum of photons known as synchrotron light.

At the SRS a beam of electrons is accelerated when it passes through a magnetic field, changing its path. The field is produced by sixteen huge 'dipole' electromagnets which constrain the beam to a roughly circular path 96 m around. Synchrotron light is emitted from all of these magnets and collected from 12 of them to feed experiments and test facilities. The light emerges like a searchlight in front of the emitting particle so it appears at a tangent to the bend. Three special magnets known as 'insertion devices' also produce light at the SRS.

The type of light produced at sources like the SRS depends on both the energy of the electron beam and the magnetic fields used to bend the beam. The higher the beam energy, the shorter the wavelength of the light produced. Strong magnetic fields will bend the beam more sharply - a greater acceleration which also gives shorter wavelength light.

The electron beam loses a great deal of energy emitting synchrotron light. To replace this energy, the electron beam bunches are 'pushed along' by radio frequency or 'RF' waves, like children on a roundabout kept turning by an adult. The RF is fed into the electron beam in four places as the beam travels around the SRS. This way the same electron beam can emit synchrotron light continuously for many hours.