Free-electron laser

The free-electron laser FELIX Radboud University, Netherlands.

A free-electron laser (FEL) is a fourth generation light source producing extremely brilliant and short pulses of radiation. An FEL functions much as a laser but employs relativistic electrons as a gain medium instead of using stimulated emission from atomic or molecular excitations.[1][2] In an FEL, a bunch of electrons passes through a magnetic structure called an undulator or wiggler to generate radiation, which re-interacts with the electrons to make them emit coherently, exponentially increasing its intensity.

As electron kinetic energy and undulator parameters can be adapted as desired, free-electron lasers are tunable and can be built for a wider frequency range than any other type of laser,[3] currently ranging in wavelength from microwaves, through terahertz radiation and infrared, to the visible spectrum, ultraviolet, and X-ray.[4]

Schematic representation of an undulator, at the core of a free-electron laser.

The first free-electron laser was developed by John Madey in 1971 at Stanford University[5] using technology developed by Hans Motz and his coworkers, who built an undulator at Stanford in 1953,[6][7] using the wiggler magnetic configuration. Madey used a 43 MeV electron beam[8] and 5 m long wiggler to amplify a signal.

  1. ^ Margaritondo, G.; Rebernik Ribic, P. (2011-03-01). "A simplified description of X-ray free-electron lasers". Journal of Synchrotron Radiation. 18 (2): 101–108. Bibcode:2011JSynR..18..101M. doi:10.1107/S090904951004896X. ISSN 0909-0495. PMC 3042323. PMID 21335894.
  2. ^ Huang, Z.; Kim, K. J. (2007). "Review of x-ray free-electron laser theory" (PDF). Physical Review Special Topics: Accelerators and Beams. 10 (3): 034801. Bibcode:2007PhRvS..10c4801H. doi:10.1103/PhysRevSTAB.10.034801.
  3. ^ F. J. Duarte (Ed.), Tunable Lasers Handbook (Academic, New York, 1995) Chapter 9.
  4. ^ "New Era of Research Begins as World's First Hard X-ray Laser Achieves "First Light"". SLAC National Accelerator Laboratory. April 21, 2009. Retrieved 2013-11-06.
  5. ^ Pellegrini, C. (2012). "The history of X-ray free-electron lasers" (PDF). The European Physical Journal H. 37 (5): 659–708. Bibcode:2012EPJH...37..659P. doi:10.1140/epjh/e2012-20064-5.
  6. ^ Motz, Hans (1951). "Applications of the Radiation from Fast Electron Beams". Journal of Applied Physics. 22 (5): 527–535. Bibcode:1951JAP....22..527M. doi:10.1063/1.1700002.
  7. ^ Motz, H.; Thon, W.; Whitehurst, R. N. (1953). "Experiments on Radiation by Fast Electron Beams". Journal of Applied Physics. 24 (7): 826. Bibcode:1953JAP....24..826M. doi:10.1063/1.1721389.
  8. ^ Deacon, D. A. G.; Elias, L. R.; Madey, J. M. J.; Ramian, G. J.; Schwettman, H. A.; Smith, T. I. (1977). "First Operation of a Free-Electron Laser". Physical Review Letters. 38 (16). Prl.aps.org: 892–894. Bibcode:1977PhRvL..38..892D. doi:10.1103/PhysRevLett.38.892.