Undulator

A device used in synchrotron radiation sources and free-electron lasers

Overview

An undulator is a periodic structure of magnets used in synchrotron radiation sources and free-electron lasers (FELs) to produce highly collimated and intense beams of electromagnetic radiation. The undulator forces a beam of electrons to undergo a series of oscillations, which results in the emission of radiation due to the synchrotron effect.

Principle of Operation

Diagram of an undulator showing the periodic magnetic structure.

The undulator consists of a series of alternating magnetic fields, typically created by an array of permanent magnets or electromagnets. As the electron beam passes through these fields, it is deflected back and forth in a sinusoidal path. This oscillatory motion causes the electrons to emit radiation at specific wavelengths, determined by the period of the magnetic structure and the energy of the electrons.

The emitted radiation is coherent and can be tuned by adjusting the magnetic field strength or the energy of the electron beam. This tunability makes undulators essential components in modern synchrotron light sources and FELs, where precise control over the wavelength of the emitted light is required.

Applications

Undulators are used in a variety of applications, including:

• Synchrotron light sources: Undulators are key components in synchrotron facilities, providing intense beams of X-rays for X-ray crystallography, spectroscopy, and other scientific research.
• Free-electron lasers: In FELs, undulators are used to generate coherent laser light across a wide range of wavelengths, from the infrared to the X-ray region.
• Medical imaging and therapy: The high-intensity X-rays produced by undulators are used in advanced imaging techniques and radiation therapy.

Comparison with Wigglers

Undulators are often compared to wigglers, another type of insertion device used in synchrotron radiation facilities. While both devices use periodic magnetic fields to produce radiation, undulators have a smaller magnetic field strength and a shorter period, resulting in narrower bandwidth and higher brightness of the emitted radiation. Wigglers, on the other hand, produce a broader spectrum of radiation with higher intensity but lower coherence.

Related pages

• Synchrotron radiation
• Free-electron laser
• Wiggler
• Magnetic field
• Electron beam