Undulator

From Free net encyclopedia

Image:Undulator.png An undulator is a device from high-energy physics and usually part of a larger installation, a synchrotron. It consists of a periodic dipole magnet structure. The static magnetic field is alternating along the length of the undulator with a wavelength <math>\lambda_u</math>. Electrons traversing the periodic magnet structure are forced to undergo oscillations and radiate. This process is very similar to Thomson scattering.

The important dimensionless parameter

<math>K=\frac{e B \lambda_u}{2 \pi m c},</math>

where e is the electron charge, B the magnetic field, m the electron rest mass and c the speed of light, characterises the nature of the electron motion. For <math>K\ll1</math> the motion of the electron can be considered linear and this is the undulator regime. If <math>K\gg1</math> the electron motion becomes highly non-linear which leads to radiation of harmonics. This is the wiggler regime.

External links

D. T. Attwood's page at Berkeley: Soft X-Rays and Extreme Ultraviolet Radiation. His lecture and viewgraphs are available online.de:Undulator hu:Undulátor