Particle accelerators were originally developed for high energy physics research into the subatomic structure of matter. The SR, which was produced in circular electron accelerators (‘synchrotrons’) was a nuisance by-produce — an energy loss process. The early stages of the utilisation of SR were therefore parasitic on the high energy physics machines whose parameters were, of course, not optimised for SR. However, SR became well recognised in its own right as a major tool in research in biology, chemistry and physics. Particle accelerators began to be designed specifically for SR production with parameters optimised solely for this work, e.g. continuous beams with long lifetimes, stable source positions and magnetic insertion devices to produce radiation of specific properties; the Daresbury Synchrotron Radiation Source (SRS) which came on-line in 1981 was the first dedicated, high energy source. Table 4.1 gives a list of storage ring X-ray sources. All modern SR sources are storage rings rather than synchrotrons. The particles used may be electrons or positrons.

Studies of the properties of the radiation from accelerated charges extend over the last 100 years. Extensive theoretical work on the radiation effects in circular electron accelerators has been done by Schwinger (1949) and Sokolov and Ternov (1968) and the theory is reviewed in Jackson (1975).