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The Defense Intelligence Agency produced this reference document, dated 31 March 2010, under its Advanced Aerospace Weapon System Applications (AAWSA) Program. It reviews the state of the art and likely evolution of high-energy laser weapons, including chemical, solid-state, fiber and free-electron lasers, as well as beam control and the history of DoD laser research. It concludes that electrically powered lasers could make megawatt-class weapons practical and that spacecraft laser weapons are conceivable within 20 years. It also recommends ways to protect spacecraft from laser damage.
“The Advance”10 pages
UNCLASSIFIED/ ,'P81l 8ffll!l*le lall!! e,11e~• FREE-ELECTRON LASERS Free-electron lasers (FELs) are unique in that they are not limited to lasing only at specific wavelengths dictated by the characteristics of a specific solid, liquid, or gaseous gain medium. FELs use a stream of "free" (unbound to atoms) electron bunches, moving at almost the speed of light, to provide the lasing medium. These short bunches of electrons are generated by a photocathode and accelerated by an RF linear accelerator which is powered by klystron tubes. The relativistic electron bunches are then passed through an alternating-polarity set of magnets, called a "wiggler" or "undulator" (Figure 8) which transversely accelerates the electrons and converts a small fraction of the electron bunches' energy into a coherent optical energy. Injected electron beam micro pulse Figure 8. Free-Electron Laser Wiggler Output radiation Spent electron beam Resonator optics on each end of the wiggler repeatedly reflect the optical bunches back through the wiggler to increase their strength. The lasing wavelength can be chosen by proper design of the wiggler and selection of the electron beam's energy. Figure 9 is a diagram of a 2 kW infrared FEL built by the Thomas Jefferson National Accelerator Facility. The highest average power FEL to-date is 10 kW. 11 UNCLASSIFIED/ ,<EiOAt OEiEiIQl.ltk Wlili &••LY
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Report, from the dia collection. The PDF is mirrored here; the original link is above. 31 pages are in the text index: search them above, or from the library's search.