Free electron laser experiments and other high power radiation sources are very demanding of beam quality for good efficiency at short wavelength. The approach to obtaining high current bright beams is examined. We conclude that very bright beams require high current density cathodes and strong magnetic fields. A new definition of beam brightness for field immersed diodes is suggested by the data. We find that perturbations on the electron beam are enhanced as a result of beam density.
C. W. Roberson,
"Bright Electron Beams For Free Electron Lasers", Proc. SPIE 0453, Free-Electron Generators of Coherent Radiation, (16 February 1984); doi: 10.1117/12.947114; https://doi.org/10.1117/12.947114