Transit-time scattering and heating of a relativistic electron beam in strong Langmuir turbulence

Abstract

A Fokker-Planck theory is developed to describe the diffusion in momentum space of a beam of relativistic electrons due to multiple transit-time interactions with an ensemble of coherent Langmuir wave packets. The theory incorporates two ingredients: a perturbed-orbit calculation of the momentum change of a test particle during a single transit-time interaction, and an ensemble average of the resulting Fokker-Planck coefficients based on the statistical properties of strong Langmuir turbulence. An approximate analytic solution of the Fokker-Planck equation is obtained for the case of a strongly collimated beam, and is used to interpret measurements of energy and pitch-angle scattering in rel..