Synchrotron Lightsource Tutorial
The Radiation in our name refers to the electromagnetic radiation spectrum. Ordinary visible light is a small part of that spectrum. Microwaves, radio waves, infrared, visible light, ultraviolet and x-rays all refer to parts of the electromagnetic radiation spectrum. At SRC our primary interest is in the range of wavelengths between the infrared and the x-ray ranges.
Common sources in the visible part of the spectrum are hot filaments (ordinary light bulbs) or discharges (fluorescent lamps). In other parts of the spectrum we make use of the fact that when charged particles are accelerated, they radiate. If electrons are accelerated back and forth in an antenna at Kilohertz or Megahertz frequencies they radiate in the radio or TV portions of the electromagnetic spectrum. If electrons are constrained to move in a circle, they will be accelerating inward, and will also radiate.
In a synchrotron, electrons move near the speed of light, causing the radiation pattern to be concentrated in the forward direction. In a storage ring like Aladdin a given bunch of electrons will be confined for long periods of time, and the result will be a stable, continuous source of light over a wide wavelength range. Electrons stay in the storage ring for hours at a time and travel a distance farther than to the planet Pluto during this time. Nevertheless, they stay on their track within a tenth of a millimeter (4 thousandths of an inch).
In the visible and near infrared, lasers and conventional sources can be intense and can be tailored for many desirable properties. At short wavelengths, x-ray tubes are intense sources, although it is difficult to collect much of the radiation. In the intermediate wavelength range, light is readily absorbed by air and all solids. It is necessary to have a source that can generate this type of radiation in vacuum, and facilities to use the out-coming light. Hence the establishment of a Center. An electron storage ring is the only practical continuum source in this wavelength range, but it is complicated and expensive to build and operate. It is more practical to bring the experiments to the source.