ABSTRACT
This chapter deals with the particle’s diffusive motion and the growth of Langmuir waves in self-consistent dynamics. This is a fundamental phenomenon observed experimentally in plasmas and travelling wave tubes. From a theoretical viewpoint, the validity of quasilinear theory was questioned by J. C. Adam et al when accounting for nonlinear wave coupling. However, in order to control the wave dynamics better and to limit noise, experimentalists left beam–plasma experiments for travelling wave-tube experiments where slow waves are amplified by a warm electron beam. The chapter discusses a diffusion coefficient for the self-consistent dynamics. It provides a heuristic derivation of the joint quasilinear equations for the particles and the waves in both time limits of interest. The chapter also deals with a brief account of the longstanding controversy about quasilinear theory and related experimental results
