Principle

Synchrotron S, Synchrocyclotron S and Cyclotron S refers to various types of accelerating S circulars.

In such accelerators an intense magnetic field makes it possible to accelerate a beam of particles. However, according to the Maxwell's equations, any particle charged moving in a non-uniform way (for example on a circular trajectory) emits a electromagnetic Rayonnement.

In the case of a Synchrotron these particles are generally electrons (more rarely of the Positron S) and turn at relativistic speeds. One can thus say that the synchrotron radiation is a electromagnetic Rayonnement emitted by electrons which turn in a storage ring.

Properties

This radiation depends on the speed of the electrons but covers a very broad part of the electromagnetic spectrum: infra-red with the hard x-rays.

It is then possible either to use a wide spectral range (infra-red spectroscopy with transform of Fourier, diffraction of Laüe), or more usually of monochromatiser this white beam to work only with one very narrow band of luminous frequencies. Within the framework of certain experiments, absorption of x-rays EXAFS or XANES for example, the possibility of varying finely the energy of the beam is a fundamental asset and makes it possible to probe precisely certain energy transitions.

The synchrotron radiation is particularly brilliant (intense and focused), it can the being 10000 times more than solar light. In the range of hard x-rays, the low divergence of the beam allows the implementation of methods of microphone-imagery, on a some fraction scale of micrometer on the most powerful lines.

Moreover, the synchrotron radiation is:

• rather easily calculable;
• very stable compared to the traditional sources;
• polarized (anisotropy);
• pulsated (observation of high-speed kinetics);
• and makes it possible to work in coherence of phase (coherent diffraction, imagery of contrast of phase).

Applications

The applications are numerous:

• in biology (Crystallography of Proteins, circular Dichroism…)
• in science of materials with vocation fundamental or applied (imagery, Diffraction)
• in physics and fundamental chemistry;
• in microphone-manufacture (deep Lithography X).