Beat-wave excitation of plasma waves

Nonlinear saturation effects associated with the generation of electron plasma waves by two high-frequency electromagnetic waves, beating at a frequency nearly equal to the electron plasma frequency, are studied. A fluid model including collisions, frequency mismatch and relativistic mass variation is used. It is shown that for large-amplitude driving waves a transition to chaos can occur, leading to plasma wave breakdown. The results may be relevant to the beat-wave current drive in tokamak devices and to beat-wave particle accelerators.