AAWSAP DIRD, Laser Lightcraft Nanosatellites, November 2010

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Free Electron Laser
High-energy free electrons from a particle accelerator (e.g., a high-voltage, high­
current electron injector gun) can emit amplified, coherent photons when they are sent
through an undulator (or "wiggler" magnets), which generates a periodically varying
magnetic field with a linear array of permanent or superconducting magnets. The
electron accelerator produces a micro-pulse of "electron bunches" moving at relativistic
speeds that are laterally accelerated (or "wiggled") by the alternating magnetic fields in
the undulator, thus releasing laser photons at optical wavelengths (see Figure 28 to
Figure 30). The optical laser radiation is amplified at the double-Doppler-shifted
wavelength of the undulator. The resulting laser beam photon energy depends on the
electron energy, the undulator period, and (weakly) the magnetic field strength. The
electron beam gets spent at the end of the lasing process.
Figure 28. Free-Electron Laser (courtesy of the Naval Post-Graduate School FEL Lab).
ron beam p ls s
optical
la er
-
•
wiggl r
pulses
-
100
pa.rtially
r fl cting
t 7ansmitting
Photon Emision
rror
r-ror
Figure 29. Free-Electron Laser Mechanism (courtesy of the Naval Post-Graduate School FEL
Lab).
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