Nonlinear absorption of intense microwave pulses.

Abstract

Free-electron lasers in the electron cyclotron frequency range have been proposed as an efficient means of heating and driving current in tokamak plasmas. The proposed free-electron laser will have short pulses (\ensuremath{\approxeq}5\ifmmode\times\else\texttimes\fi{}${10}^{\mathrm{\ensuremath{-}}8}$ sec) with a peak power of (4--8)\ifmmode\times\else\texttimes\fi{}${10}^{9}$ W and electric fields within the plasma in the range ${10}^{5}$--${10}^{6}$ V/cm. At these high intensities nonlinear effects compete with thermal effects in the absorption of microwave power. Analytic and numerical calculations of the nonlinear absorption are presented.