radiation covered many wavelength regimes due to the nature of the bending magnet emission. In addition, the machines produced rather large photon source sizes as the electron beam emittance was large and not intended for (or ideal for) synchrotron radiation applications. Second-generation machines are dedicated machines for synchrotron radiation users and employ bending magnets as the primary source of synchrotron radiation. The beam emittances were designed by the machine architects to be smaller in order to provide users with a smaller source size and greater brilliance. Third-generation machines are dedicated for synchrotron radiation users and were designed to accommodate many so-called insertion device magnets, such as undulator and wiggler magnets. Undulator magnets generate narrow spectral lines, which enhances the overall photon brilliance. Next-generation light sources involve an optical gain mechanism, with the goal of transverse and longitudinal optical coherence such as in an FEL.



1. A.J. Balkcum, D.B. McDermott, R.M. Phillips, and N.C. Luhmann, “High-Power Coaxial Ubitron Oscillator: Theory and Design,” IEEE Transactions on Plasma Science 26: 548-555 (1998).


2. D.A.G. Deacon, L.R. Elias, J.M.J. Madey, G.J. Ramian, H.A. Schwettmann, and T.I. Smith, “First Operation of a Free-Electron Laser,” Physics Review Letters 38: 892-894 (1977).


3. National Research Council, Free Electron Lasers and Other Advanced Sources of Light: Scientific Research Opportunities (Washington, D.C.: National Academy Press, 1994).

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