A two-dimensional nonlinear Fokker-Planck analysis is performed for collisional relaxation of a velocity distribution function of electrons heated in an ultra-short pulse laser-irradiated fully ionized plasma. The effect of electron-electron (e-e) collisions on inverse bremsstrahlung heating due to the electron quiver following tunnelling and/or above-threshold ionization (ATI) and electron-ion collisions is studied. It is found that the difference in very low-energy population between the cases with and without e-e collisions can reach up to 20-30% over the laser pulse length. This indicates that the electron self-collision may not be neglected for evaluation of the recombination rate due to slow electrons. Also discussed is the two-dimensional structure of the velocity distribution and the one-dimensional energy spectrum.
Electron energy distribution function during second harmonic ECRH plasma breakdown