Free Electron coherent sources: From microwave to X-rays

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The term Free Electron Laser (FEL) will be used, in this paper, to indicate a wide collection of devices aimed at providing coherent electromagnetic radiation from a beam of “free” electrons, unbound at the atomic or molecular states. This article reviews the similarities that link different sources of coherent radiation across the electromagnetic spectrum from microwaves to X-rays, and compares the analogies with conventional laser sources. We explore developing a point of view that allows a unified analytical treatment of these devices, by the introduction of appropriate global variables (e.g. gain, saturation intensity, inhomogeneous broadening parameters, longitudinal mode coupling strength), yielding a very effective way for the determination of the relevant design parameters. The paper looks also at more speculative aspects of FEL physics, which may address the relevance of quantum effects in the lasing process.
Original languageEnglish
Pages (from-to)1 - 51
Number of pages51
JournalPhysics Reports
Publication statusPublished - 12 Apr 2018
Externally publishedYes


All Science Journal Classification (ASJC) codes

  • Physics and Astronomy(all)

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