Strong-Signal Theory of a Free-Electron Laser

Abstract

The strong-signal regime of a free-electron laser is analyzed in terms of a set of "generalized Bloch equations." We show that for current free-electron-laser configurations the saturation will be reached for a field on the order of ${10}^{7}$ V/m, with an efficiency at saturation of 5\ifmmode\times\else\texttimes\fi{}${10}^{\ensuremath{-}3}$. However, a strong reshaping of the electron distribution may alter the efficiency of free-electron lasers in cases where the electron beam is recycled from one shot to the next.