Brilliance of X-rays

There are several different types of synchrotron light source at the SRS.

Sixteen dipole magnets keeping the electron beam on its circular path all produce a broad spectrum of wavelengths, with the most intense output in the soft X-ray region - a wavelength of about 4x10^-10 m. There are also two special types of magnets, the so-called 'insertion devices' placed between the dipoles. The first of these is known as an 'undulator' magnet. The undulator is formed from a periodic array of permanent magnets, that are arranged to gently wave the electron beam in a sine-like path through the magnet's length. Synchrotron light results from each undulation, and constructive interference between these emissions gives a very bright and narrow light beam.

One of the sixteen SRS dipole magnets.

The 6 Tesla superconducting wiggler magnet.

 The second type of insertion device is a 'wiggler' magnet or 'wavelength shifter', so called because it shifts the most intense output further into the shorter or 'hard' X-ray region. There are two such magnets in the SRS. The wigglers are superconducting magnets; electromagnets formed from coils having no electrical resistance, and therefore generating extremely high magnetic fields. The high fields cause the stored electron beam to effectively take a 'hairpin bend', a huge acceleration generating very short wavelength light. The magnets are bathed in liquid helium at a temperature of -269° C to keep them superconducting.